Ian West, Romsey, Hampshire
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Related Field Guides - Portland and Chesil Beach
Portland Field Guide - Introduction
BIBLIOGRAPHY AND INTERNET LINKS FOR GEOLOGY OF THE ISLE OF PORTLAND
Isle of Portland - Internet Links
Some of these may provide useful geological detail. Some provide general background information on the peninsula and its environment. Some short extracts have been provided to give an idea of the content.
Portland Bill
Portland Harbour
Portland Bibliography
Portland Dinosaurs
Portland - Mutton Cove and West Cliffs
Portland Fossils
Withies Croft Quarry Wall, Portland
Chesil Beach - Introduction
Chesil - Storms, Floods
Chesil - Pebbles - General
Chesil - Magnetite, Lodestone pebbles
Chesil Beach - Geological Bibliography
Fleet Lagoon
Bridport - East Cliff (and W end of Chesil)
For Chesil Beach Bibliography see Chesil Beach Bibliography
MAIN BIBLIOGRAPHIC LISTING -
Publications relevant to the geology, geomorphology and some other aspects of the Isle of Portland
Allen, T.D. 1863. The Portland fissures with human remains. Geologist, 6, 209, 293.
Arkell, W.J. 1947. The Geology of the Country around Weymouth, Swanage, Corfe and Lulworth. Memoir of the Geological Survey, 386 pp. Explanation of Sheets 341, 342, 343, with small portions of Sheets 327, 328 and 329. By W.J. Arkell, M.A., D.Sc., with contributions by C.W. Wright, M.A. and H.J. Osborne White, F.G.S. London, Published by Her Majesty's Stationery Office, 1947, reprinted 1953. [This classic publication covers almost the same area as that of Strahan's 1898 memoir and is an update to 1939 with some small additions to 1944.]
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Bastos
, A., Kenyon, N. and Collins, M. 2002. Sedimentary processes, bedforms and facies, associated with a coastal headland: Portland Bill, Southern UK. Marine Geology, 178, Issue -3-4, pp. 235-258.
Abstract: This investigation presents new findings on the sedimentary processes and deposits associated with a coastal headland, in a mixed tidal-wave setting, using data compilation (bathymetric and sediment distribution maps), collected field data (side-scan sonar and sea-bed sampling) and sand transport modelling. Sand transport pathways are described: (a) on the basis of coupled-system seabed morphology/sand distribution; and (b) from bed shear stress and (medium-grained) sand transport rate simulations. The presence of a sequence of sedimentary deposits, associated with a complex suite of bedforms and sedimentary facies within an overall framework of limited sediment supply, represents a gradient in shear stress and sand transport towards the headland. These sequences are observed on both sides of Portland Bill, tending towards a symmetrical distribution. The sedimentary facies distribution is combined with sand transport rates and maximum bed shear stress distribution, to suggest a conceptual model for sand dispersal and deposit formation around headlands. Sand dispersal can be explained in terms of a headland-associated eddy/bedload convergent zone concept. Maximum bed shear stress is observed at the tip of the headland and is associated with bedrock exposed on the seabed. The sequence of sedimentary deposits away from the headland is: sandbanks (Shambles and Porland Banks); sand/gravel flats; sand shoals (Adamant and West Shoals); and rippled sand sheets. The banks lie in an area of very high bed shear stress (u* = 0.08 metres per second); this is greater than that for other tidal sandbanks, not associated with headlands. Bank formation is the result of the strong convergent (transport) component, enhanced by the development of transient headland eddies. The sandbanks are to some extent also morphologically controlled, i.e. the Portland Bank is affected by the deep bathymetry to the west side of Portland Bill. The principal characteristics of headland-associated eddy/bedload convergent zones is the development of bed shear stress convergent zones, on both sides of the headland. Two conceptually distinct regions of sedimentary processes, associated with the coastal headlands are recognised: (a) an inner zone, with increasing gradients in sand transport and bed shear stress towards the headland; and (b) an outer zone, in which sand transport is away from the headland, associated with a decrease in the shear stress. These zones merge into a bed shear stress (sand bedload transport) convergent zone, which enhances the formation of sandbanks around headlands. Thus, headland-associated sedimentary deposits are a complex system, compared with the occurrence of isolated sandbanks described elsewhere. The identification of a sequence of deposits related to and extending much further from the headland than previously supposed, demonstrates that the 'tidal stirring concept' of headland-associated sandbanks may explain the formation of headland-associated sandbanks; however, it ignores the presence of a suite of sedimentary deposits around such headlands. The conceptual model proposed here provides a sedimentological perspective on the formation and occurrence of headland-associated deposits, including sandbanks... The authors (Alex C. Bastos, Neil H. Kenyon and Michael Collins) are at the School of Ocean and Earth Science, and the Challenger Division, University of Southampon, Southampton Oceanography Centre, Empress Dock, Southampton, SO14 3 ZH.
Bastos, A.C., Collins, M. and Kenyon, N.H. 2003.
Morphology and internal structure of sand shoals and sandbanks off the Dorset coast, English Channel.
Sedimentology, vol. 50, issue 6, pp. 1105-1122.
By Alex C. Bastos, School of Ocean and Earth Science, Michael Collins, School of Ocean and Earth Science and Neil H. Kenyon, Challenger Division, Southampton Oceanography Centre, [now National Oceanography Centre, Southampton] University of Southampton, European Way, Southampton SO14 3ZH, UK.
Bruce
, P. 2001. Inshore along the Dorset Coast. Third Edition, Boldre Marine, Lymington. 134pp. Paperback. ISBN 1-871680-26-3 By Peter Bruce. Price was £14.95. From the back cover blurb: This is a book for seafarers and landsmen who have reason to visit the exceptionally beautiful and interesting east Dorset coast. It covers the area from Christchurch Bay to Portland Bill and gives in detail all the nautical lore, delights, tidal streams and history that most people would ever want to know. Every bay, every landing place and every feature has been surveyed in detail and researched to provide expert local knowledge. Furthermore the text is richly illustrated by superb aerial and sea level colour photographs which add considerably to the value of this unique book for those who venture on the water in any kind of craft, or for those who are curious about marine aspects of the coastline. [This book is very useful for local names and coastal detail for the eastern Dorset coast. This edition has very good colour photographs, many of them aerial photographs. Chapter 9, p. 102 et seq, is on Portland Harbour. Chapter 10 p.102 et seq., is on the Fleet Lagoon.]
Brunsden
, D. and Goudie, A. 1981. Classic Coastal Landforms of Dorset. Geographical Association, Landform Guides, No. 1, 39 pp.
Robert Damon, 1814-1899, was a well-known Dorset geologist and collector of and dealer in fossils. He was born in Weymouth, with origins in a Flemish family. He ran a fossil shop at Augusta Place, the Esplanade, Weymouth. This shop is now a fish and chip shop (information kindly provided by his great, great grandaughter - Carole Burridge - nee Carole Damon, who lives in Bridport). Robert Damon was a Member of the Imperial Natural History Society of Moscow, and visited Russia in 1883, bringing back samples. His books are extremely interesting, with many diverse footnotes and sidelines. Robert Damon made a private collection of 400 Dorset fossils to illustrate his books. The Victoria Museum, Australia has ichthyosaurs from Damon, and many other museums contain fossils of his.
Damon
, R. 1860. Handbook to the Geology of Weymouth and the Isle of Portland; with Notes on the Natural History of the Coast and Neighbourhood. By Robert Damon. Accompanied by a map of the district, geological sections, plates of fossils, coast views, and numerous other illustrations. London, Edward Stanton, 6 Charing Cross, 1860. This edition is available online in Google Book Search. The second edition, listed below is mostly the same but with some additions.
Damon
, R. 1884. Geology of Weymouth, Portland, and Coast of Dorsetshire, from Swanage to Bridport-on-the-Sea: with Natural History and Archaeological Notes. New and Enlarged Edition (2nd Ed.), Weymouth, R.F. Damon, London, Edward Stanford. 250p. With a colour geological map of part of the Dorset coast, and including a log of the Purbeck strata of Durlston Bay, Swanage, by H. W. Bristow and Prof. E. Forbes (although note that it contains a small error). (A copy of Damon's second edition is in the possession of Ian West)
Ensom, P.C. 2002. Vertebrate trace fossils in the Purbeck Limestone Group of Southern England. Pp. 203-220 in:
Milner, A.R. and Batten, D.J. (Editors) 2002. Life and environments in Purbeck times. Special Papers in Palaeontology, No. 68, Palaeontological Association, London, 268pp. Abstract: The Purbeck Limestone Group (late Jurassic-early Cretaceous) contains a rich vertebrate trace fossil fauna. Research on this fauna has been almost entirely concerned with dinosaur tracks. By contrast, the feeding traces and coprolites, which are occasionally abundant, have received little attention. The implications of some recent papers, including those where ichnotaxa are assigned, are considered along with the stratigraphic and geographic distribution of reptilian tracks. A plan of the principal footprint horizon at Townsend Road, Swanage, is presented and the more unusual aspects of the site illustrated. An appendix gives a comprehensive listing of published and manuscript accounts dealing with footprints from these strata. Some of the neglected feeding traces and coprolites are described and illustrated for the first time. [Although this is mostly on dinosaur footprints etc from the Dorset mainland, it mentions a Portland occurrence (the Jane Francis record) and is relevant to new discoveries of tracks in the Hard Slatt.]
Ensom, P.C. and Delair, J.B. 2008. Dinosaur tracks from the Lower Purbeck strata of Portland, Dorset, southern England. Proceedings of the Ussher Society.
Francis
, J. E. 1983. The Fossil Forests of the Basal Purbeck Formation (Upper Jurassic) of Dorset, Southern England: palaeobotanical and palaeoenvironmental investigations . Unpublished Ph.D. Thesis, University of Southampton. 295 pp. By Dr. Jane Elizabeth Francis. Abstract: During the Upper Jurassic, coniferous forests grew adjacent to the Purbeck evaporitic basin in Dorset: The palaeobotany of the forests is described for the first time and the Purbeck forest environment reconstructed. The basal Purbeck Formation of Dorset was deposited during minor transgressive and regressive phases on the borders of a shallow hypersaline basin. The sediments include evaporites, hypersaline intertidal algal stromatolitic sediments and lagoonal pelletoid silts interbedded with supratidal algal mat sediments. The unusual features are brecciated calcrete and calcareous marls representing former forest soils. The trees which grew in the rendzina-like palaeosols of the Lower and Great Dirt Beds are now preserved in situ as silicified tree stumps and branches. They were drowned by rising hypersaline water and preserved within mounds of algal stromatolitic sediment. The wood was rapidly silicified by length-slow chalcedony (quartzine), a type of silica commonly associated with evaporitic environments. The fossil forests were dominated by one type of conifer belonging to the extinct family Cheirolepidiaceae. The wood of this is designated Protocupressinoxylon sp. A nov., the small scale-like leaves are Cupressinocladus valdensis (Seward) Seward and the small male cones Classostrobus sp. Alvin, Spicer and Watson. The tree is a source of Classopollis Pflug pollen so widespread in the Jurassic. A reconstruction of this Purbeck tree, based on evidence from fossil remains, is presented. The trees were monopodial with low branches and shallow spreading roots and formed fairly dense, closed forests. A few other conifer species were also present but much less abundant and cycadophytes (Bennettitales) are also represented by their silicified stems. The miospore assemblage from the palaeosols is dominated by Classopollis pollen (70% of samples), but also represents a rather poor flora of filicalean and lycopsid plants. Comparison with modern tree-ring data from semi-arid regions suggests a Mediterranean-type of climate for the Purbeck with warm, wet winters and hot, dry summers. The markedly seasonal nature of the climate is supported by sedimentary and faunal evidence such as ephemeral lake sediments containing both a freshwater fauna and flora plus evaporites. Modern analogues to the Purbeck environment have been found in the Mediterranean areas of the southern parts of Australia. The environment of the Callitris forests of Rottnest Island, Western Australia, appears remarkably similar to that of the~Purbeck forests. This type of seasonal, semi-arid climate during the Upper Jurassic accounts for the paradoxical association of evaporites with well developed forest vegetation. It contrasts with the widely held view, that the Jurassic climate was warm and equable. The reconstruction of the Purbeck trees and forest environment may serve as a model for other Upper Jurassic and Lower Cretaceous vegetation.
Francis, J.E. 1983b. The dominant conifer of the Jurassic Purbeck Formation, England. Palaeontology, 26, 277-294. Abstract: Fossil trees are preserved in situ in fossil soils in the Lower Purbeck (Upper Jurassic) strata of Dorset. Silicified tree stumps, still rooted in the soils, stand erect and protrude into the overlying limestones. Numerous trunks and branches lie on the soils, which also contain conifer shoots. The forests were dominated by one kind of conifer with wood, named here as Protocupressinoxylon purbeckensis sp. nov., foliage belonging to the species Cupressinocladus valdensis (Seward) Seward and with male cones yielding Classopollis pollen. A reconstruction of the anatomy and habit of the tree is given. The Lower Purbeck palaeoclimate is discussed using the evidence of tree growth rings and the character of the associated sediments.
Francis, J.E. 1984. The seasonal environment of the Purbeck (Upper Jurassic) fossil forests. Palaeogeography, Palaeoclimatology, Palaeoecology, 48, 285-307. Abstract: In the basal Purbeck Formation of Dorset a paradoxical association of evaporites and fossil forest vegetation is found, representing well-developed gymnosperm forests which grew on the borders of the shallow, hypersaline Purbeck lagoon which covered southern England during the late Jurassic. The dominant tree was a cheirolepidiaceous conifer which appears from its morphology to have been adapted to growing in a semi-arid environment. The narrow and variable growth rings of the trees indicate that conditions were marginal for tree growth and highly irregular from year to year. Comparison with modern tree-ring data suggests that the Purbeck climate was of Mediterranean type, with warm wet winters when the trees were able to grow but with hot, arid summers suitable for the formation of evaporites.
The seasonal nature of the climate is also reflected in adjacent sediments, including a clay containing both fresh-water fossils and evaporites, calcrete crusts in the palaeosols, the nature of the silicification and the presence of seasonal crustaceans in finely laminated shales. Analogous modern environments for both the forests and the seasonal lagoonal sediments can be found in the Mediterranean-type climatic regions of South Australia.
This evidence shows that within the "equable" Jurassic climate marked seasonal variations affected the whole environment. The seasonal nature of this climate supports recent palaeoclimatic models which propose that such a climate prevailed along mid-latitude continental margins during the Mesozoic.
Francis, J. E. 1986. The Calcareous Paleosols of the Basal Purbeck Formation (Upper Jurassic) Southern England. p. 112-138 in: Wright, V.P. (Ed.) Paleosols: Their Recognition and Interpretation. Blackwell, Oxford. ISBN 0-632-01336-2. By Dr. Jane Francis of Leeds University. Summary:
Rendzina paleosols are preserved within a sequence of marginal continental deposits of algal stromatolitic and pelletoid limestones, constituting the basal part of the Lower Purbeck Formation in Dorset. The Great Dirt Bed is the most well-developed paleosol exhibiting a characteristically simple A/C rendzina profile, consisting of a dark organic-rich horizon overlying limestone bedrock. The main component of the matrix of the A-horizon is decomposed plant debris. There is little evidence of the activity of soil organisms and a notable absence of a pelletoid moder fabric, the faecal pellet textures typical of modern rendzinas. The upper O-horizon of undecomposed plant litter is also lost. This soil supported a conifer forest of slow-growing shallow rooted trees, now preserved in situ as silicified tree trunks and carbonized roots. Pebbles derived from the underlying limestone are incorporated in the soil matrix. Some consist of blackened sediment derived from a desiccated and fractured organic-rich deposit previously formed on the margins of the adjacent lagoon. The semi-arid, seasonal Purbeck climate promoted the formation of laminated and mottled deposits of secondary carbonate or calcrete, present as micritized bedrock, laminar rinds and cement around pebbles. This was itself brecciated by the soil processes and probably also by the mechanical action of the tree roots, then to become incorporated into the solum as pebbles. The Lower and Basal Dirt Beds are immature forms of rendzinas, with similar simple profiles of organic-rich layers with high carbonate content, overlying marl and devoid of large pebbles. The Lower Dirt Bed also supported a forest of conifers and cycadophytes. Each paleosol is capped by algal limestone, which originated as algal-bound sediment formed when rising saline lagoon water successively inundated the forests. This covered the tree stumps and the top of each soil with a protective layer of sediment, ensuring the rather exceptional preservation of these paleosols with in situ tree stumps. [Key paper on the Basal Purbeck Dirt Beds of Lulworth and Portland.]
Francis, J. 1996. Paddling in the Portlandian: a new record of dinosaur footprints from the Purbeck/Portland transition, Portland. Palaeontological Association Newsletterr, No. 32. Abstracts and Programme for the 1996 Annual Meeting (40th). Edited by Smith, P.M. and Thomas, A.T., 1- xxxii + 12pp. One paragraph only (as below) on page xv of the Abstracts volume. "A new set of dinosaur footprints has been discovered on the Isle of Portland on an exposed bedding surface in a disused quarry. The footprints are shallow impressions of small (up to 14 cm in length broad three-toed prints, very similar to those made by bipedal tridactly ornithopods such as Iguanodon . They do not appear to form a distinct trackway, more of a meandering stroll assemblage. The footprints occur in the upper surface of a transitional bed between the underlying marine shelly oolites of the Portland Stone Formation and overlying palaeosols and algal limestones of the Purbeck Lulworth Formation. This bed represents a change from high energy carbonate shelf facies to shallower, lower energy conditions prior to the onset of terrestrial soils/hypersaline lagoon environments. This is the lowest stratigraphical occurrence of footprints known in the Purbeck Group, since previously recorded footprints occur much higher in the Middle Purbeck Durlston Formation. These footprints show that ornithopod dinosaurs paddled happily in the shallows of the Portlandian seas in the Mediterranean climate that prevailed at that time." End of Abstract. By Jane Francis, Department of Earth Sciences, University of Leeds, Leeds, LS2 9JT. [The location is believed to be a small abandoned quarry of Portland Stone with basal Purbeck Caps and Dirt Beds above Freshwater Bay, on the east cliffs of Portland, map reference 691702, but nothing is very obvious there at present. The bed is the Transition Bed, a thin and laminated pelletoidal limestone, characterised in many places by a fauna of small lagoonal gastropods, such as Hydrobia as moulds and with some foraminifera visible in thin-section. It is fused directly to the top of the Portland Freestone which is characterised by the shells of large marine molluscs. IMW]
- There follows, effectively a book, with numerous pages of text, and with small illustrations. There is a wealth of information, which if printed out would occupy 100 or more pages of text. Chapters 1, part of the History of Wyke Regis, includes short sections on: The Formation of Chesil Beach and the Fleet, The Geology of Wyke, Fossils in Wyke. There is interesting information about the Smallmouth Sands which were once very extensive at low water (see section on: The Old Road to Portland).
Hounsell, S.S.B. 1962. The quarrying of Portland Stone. The Quarry Manager's Journal, 1962. Also reprinted as a separate. Pp 1-8 of reprint.
House, M.R. 1958. The Dorset Coast from Poole to the Chesil Beach. Geologists' Association Guides, No. 22, 21pp.
House, M.R. 1968. Purbeckian calcareous algae. In Dorset Natural History Reports - 1967 - Geology. Proceedings of Dorset Natural History and Archaeological Society for 1967. vol. 89, p.41-45.
House, M.R. 1970. The Portland Stone on Portland. Proceedings of Dorset Natural History and Archaeological Society, 91 (for 1969), 38-39.
House, M.R. 1989. Geology of the Dorset Coast. Geologists' Association Guide, 169pp, 39 text-figs and 34 monochrome plates. September 1989. Paper-back. ISBN 0 7073 0485 7.
House, M.R. 1993. Geology of the Dorset Coast. Geologists' Association Guide No. 22. 2nd edition, 164pp., 43 text-figs (mostly cliff diagrams and maps) and 32 plates, some in colour. Paper-back. ISBN 0 7073 0485 7.
Extract from Preface: "This guide aims to provide a general introduction to what may may be seen and where. Emphasis is placed on the localities and the precise discrimination of the stratigraphic successions. It is hoped that in this way new observations can be better integrated with earlier work and thus form a more scientific basis for individual study, thought and interpretation and argument. Most emphasis is placed on the Jurassic rocks because these are such an international standard. Rather less detail is given on the Cretaceous and Tertiary rocks because these rocks are as well or better seen elsewhere, and the Dorset Chalk cliffs, being mostly vertical, are also dangerous. In any case, with such a wealth of geology to describe, some selection has been essential. The introductory sections on Sedimentology and Palaeontology have been added by request to introduce specialist terms to the general reader. "
Hunt, C.O. 1987. Dinoflagellate cysts and acritarch assemblages in shallow-marine and marginal-marine carbonates: the Portland Sand, Portland Stone, and Purbeck Formations (Upper Jurassic/Lower Cretaceous) of southern England and northern France. Pp 208-225 in: Hart M.B. (editor) Micropalaeontology of Carbonate Environments, Ellis Horwood.
Jarzembowski, E.A. 1996. Towards a revision of Purbeck insects: Protogryllus, Panorpidum, Pleciomyia and Prohousea Nom. Nov. Proceedings of Dorset Natural History Archaeological Society, for 1995, vol 117, 155-157.
Jarzembowski, E.A. and Coram, R. 1997. New fossil insect records from the Purbeck of Dorset and the Wealden of the Weald. Proceedings of Dorset Natural History and Achaeological Society, for 1996, vol.118, 119-124. Authors' Abstract: This paper updates the checklist (Jarzembowski, 1993) and subsequent articles (Clifford et al. 1994; Coram et al. 1995) in previous Proceedings. Recent discoveries are reviewed and Purbeck fossil insects collected by the Revd O. Fisher last century and deposited in the Sedgwick Museum, Cambridge, have been re-examined. Some groups are traced through the non-marine Lower Cretaceous of southern England. (End of Authors' abstract). [Bugs, flies etc from the Middle Purbeck of Durlston Bat and dragonfly larvae from the Lower Purbeck of Durlston Bay and Freshwater Bay, Portland.]
Kemp, J.P. undated - 199?. The Book of the Chesil Beach. 22pp. Small paperback booklet with interesting general and historic information. Price £2.50 obtainable from the Chesil Beach Centre.
Contents:
Example extract - Introduction:"The features of the Dorset coast between Highcliffe in the east and Lyme Regis in the west are the result of thousands of years of marine and sub-aerial processes acting upon a wide range of geological materials whilst climate, sea-level and the human use and modification of the coast have changed significantly. Coastal processes act on timescales that range from the few seconds of a wave breaking to the many millennia of sea-level change. Similarly, these processes also occur on spatial scales of a few millimetres to the scale of the English Channel and beyond. For example, a pebble falling from the cliffs at Budleigh Salterton in East Devon several thousand years ago and found today on Chesil beach has probably made a journey equivalent to the distance from Earth to the planet Neptune. During all of that time, the combined effects of waves, tides and currents have moved the pebble up, down and along the shore and buried within the beach as well."
Milner, A.C. 2002. Theropod dinosaurs of the Purbeck Limestone Group, southern England. Pp. 191-201 in: Milner, A.R. and Batten, D.J. (Editors) 2002. Life and environments in Purbeck times. Special Papers in Palaeontology, No. 68, Palaeontological Association, London, 268pp. Abstract: A small, probably juvenile theropod dinosaur, Nuthetes destructor Owen, 1854 from the Berriasian Middle Purbeck Beds, Isle of Purbeck, regarded hitherto as a megalosaur, is redescribed as a dromaeosaur on the basis of distinctive tooth and tooth denticle characters. This represents the first dromaeosaur record from Britain and fills a gap in the stratigraphical occurrence of the family in Europe between the Kimmeridgian in Portugal and the Barremian in Spain. The Purbeck fauna also includes evidence of a large maniraptoran, perhaps a dromaeosaur, although it is not at present possible to determine whether it represents the same taxon as Nuthetes. At least one other theropod taxon is present in the Purbeck Limestone on the basis of isolated teeth which closely resemble those of allosauroids. [By Angela C. Milner, The Natural History Museum, London.]
Morris, S. 1985 (new edition 2004). Portland, an Illustrated History. By Stuart Morris. Dovecote Press. ISBN 0 946159 34 3. The first full history of the 'Island' and the Royal Manor of Portland, illustrated with 150 photographs, drawings and maps. Less than 10 miles square, a solid block of limestone jutting our sharply into the Channel, Portland's virtual isolation until the 19th century delayed change and gave its inhabitants a highly individual character. For centuries quarrying and smuggling were its principal occupations. Stuart Morris, himself a Portlander, has gone back to original sources to help describe its long and eventful past. Price: £8.95.
Morris, S. 19.. Portland. Discover Dorset. Dovecote Press. Paperback. ISBN 1 874336 49 0. Price: £4.95. By Stuart Morris.
The Island and Royal Manor of Portland is unique in Great Britain, and even today retains an atmosphere and identity that are all its own. This is a portrait of the Island that both brings its past to life and adds to our enjoyment of Portland as it is today.
Morris, S. 1989. Portland in Old Picture Postcards. European Library, Zaltbommel, the Netherlands, Third Edition. ISBN 90 288 2647 5 /CIP. (First edition was in 1983). By Stuart Morris. [76 monochrome photographs]
Morris, S. 1990. Portland Camera. The Dovecote Press. Stanbridge, Wimborne, Dorset. ISBN 0-946159-79-3. By Stuart Morris. [This is a low-cost paperback book containing 160 very intereting, monochrome photographs with explanatory captions. Also a two page introduction. The 22 photographs in the sections on "Around the Coast" and the "Island of Stone" are of particular interest to geologists. The section on Chiswell has 21 photographs showing the southeastern end of the Chesil Beach, some in storm and flood conditions. The "Transport and Industry" section has a photograph of a 1907 landslide collapsing the line of the Easton and Church Hope Railway on the East Weares cliffs. There are several good-quality aerial photographs. It is an essential book for following the history of coastal and quarrying features of the Isle of Portland. The book can be obtained from the publisher and is likely to available on sale in the bookshop at Easton, Isle of Portland.]
Morris, S. (year - ?). An Index of Portland Place Names.
Palmer, S. 1970b. A fossil ivory pendant from Portland Bill. Proceedings of Dorset Natural History and Archaeological Society,91, 172-173.
Palmer, S., 1971. Second report on excavations at Portland Site 1, 1967 to 1968. Proceedings of Dorset Natural History and Archaeological Society, 92, 168-180.
Palmer, S., 1998. Ancient Portland - Archaeology of the Isle. Portland.
Palmer, S. 1999. Culverwell Mesolithic Habitation Site, Isle of Portland, Dorset. Excavation Report and Research Studies. British Archaeological Reports, British Series, 287, Oxford.
Palmer, S. 2004. Late Palaeolithic site, Castletown, Portland, Dorset. Proceedings of Dorset Natural History and Archaeological Society for 2003, 125, 13-21. By Susann Palmer.
Palmer
, T.J. 1994 - in: Fursich
, F.T., Palmer, T.J. and Goodyear, K.L. 1994. Growth and distintegration of bivalve-dominated patch reefs in the Upper Jurassic of southern England. Palaeontology, vol. 37, Part 1, pp 131-171.
By Franz T. Fursich, Timothy J. Palmer and Kay L. Goodyear.
Pugh, M.E. and Shearman, D.J. 1967. Cryoturbation structures at the south end of the Isle of Portland. Proceedings of the Geologists' Association. 78, 463-471.
Seward, A.C. 1897. On a new fossil cycad from the Isle of Portland, Geological Magazine for 1897, p. 313.
Wimbledon
, W.A. 1987. Rhythmic sedimentation in the Late Jurassic-Early Cretaceous. Proceedings of the Dorset Natural History and Archaeological Society, 108 for 1986, 127-133. Most of this paper is on the Portland Group. An Appendix refers to Purbeck nomenclature. Abstract: A number of shallowing and deepening phases is described in the late Kimmeridgian - Berriasian interval. Eleven deepening / transgressive events are noted in the most complete Dorset section. A preferred lithostratigraphy for these beds is compared to previous lithostratigraphy, and "event correlations" are critically examined.
Wimbledon, W.A. and Cope, J.C.W. 1978. The ammonite faunas of the English Portland Beds and the zones of the Portlandian Stage. Journal of the Geological Society, London 135, 183-190.
Example extract:
Wimbledon, W.A., Allen, P., Parker, A., Ogg, J., Algeo, T., Hunt, C.O. and Nunn, J. in preparation 1997. The Kimmeridge-Wealden transition in the Portland, Lulworth and Swanage districts; the Portland-Purbeck type sections - their stratigraphy, palynology, clay mineralogy, heavy minerals and palaeomagnetism.
Wimbledon, W.A. and Hunt, C.O. 1983. The Portland - Purbeck junction (Portlandian - Berriasian) in the Weald, and the correlation of latest Jurassic - early Cretaceous rocks in southern England. Geological Magazine, 120, 267-280.
West, I.M. 1964. Evaporite diagenesis in the Lower Purbeck Beds of Dorset. Proceedings of Yorkshire Geological Society, 34, 315-330. [Petrographic evidence of vanished evaporites in the Caps and Broken Beds - pseudomorphs, celestite, lutecite etc. Diagenetic history established.] Abstract: Five stages have been determined in the diagenetic history of the calcium sulphate beds of Lower Purbeck age in Dorset, particularly by reference to abundant pseudomorphs and other relict textures and structures preserved in late-formed gypsum and in secondary silica and calcite. The weight of the overburden is thought to have controlled the changes. Occurrences are described of minerals, including celestite, calciostrontianite, lutecite and quartz remaining after the removal in solution of gypsum. A description is also given of secondary limestones which occur particularly in the Caps and Broken Beds. They are shown to be almost entirely replacements of original sulphate deposits.
West, I.M. 1965. Macrocell structure and enterolithic veins in British Purbeck gypsum and anhydrite. Proceedings of the Yorkshire Geological Society, 35, 47-58. Abstract: A nodular structure, here termed "macrocell structure" [nodular or chicken-wire structure] , is commonly associated with enterolithic veins in the British Purbeck gypsum and anhydrite. The veins and macrocell structure preceded the brecciation that gave rise to the Broken Beds and were present in early secondary anhydrite. Both structures probably originated when primary gypsum was undergoing compaction before the lithification of the associated marl, and have not resulted from hydration of anhydrite. A sequence of diagenesis for Purbeck calcium sulphate with macrocell structure is established, comparable to that previously elaborated [West, 1964a] for the calcium sulphate with [the microscopic] net-texture. Similar features are present in other calcium sulphate deposits.
West, I.M., 1969. Contribution in International Field Symposium on the British Jurassic; Guide for Dorset and South Somerset. Ed. H.S. Torrens, A60-61.
West, I.M. 1973. Vanished evaporites - significance of strontium minerals. Journal of Sedimentary Petrology, 43, 278-279. [On indicators of former evaporites such celestite and associated lutecite, the oblique-extinguishing variety of chalcedony; also length-slow chalcedony - quartzine etc.] Extracts: 'In a recent paper, Folk and Pittman (1971) have clearly indicated the importance of lutecite and quartzine varieties of chalcedony as evidence for the former presence of evaporites. Although lutecite has been successfully employed by the present writer for the detection of former gypsum deposits removed by dissolution (West, 1964; West, Brandon and Smith, 1968), confirmatory evidence is usually necessary. Fortunately, those processes which cause the removal of evaporites in solution frequently also result in their partial replacement by other minerals. Groundwater with bicarbonate ions may partly convert calcium sulphate deposits to calcium carbonate before dissolution of any remaining gypsum. Examples of such calcitised evaporites have been described by West (1964), Shearman and Fuller (1969) and other authors. In a dolomitic succession the calcitic nature of such replacements may be conspicuous. Pseudomorphs, relics of anhydrite in euhedral quartz crystals, and traces of net-texture (West, 1964) or nodular structure (West, 1965) may be present in any replacements or residues of dissolved evaporites. A positive indication of the former presence of calcium sulphate is the occurrence of celestite. This mineral is rarely found in sedimentary deposits other than evaporites, replaced evaporites or insoluble residues of evaporites. The related mineral barite is not so restricted. Associations of celestite with present or former evaporites have been described by Lacroix (1897), Zaritsky (1961), West (1964), West, Brandon and Smith (1968) and many other authors. Celestite is, in most cases, formed by the replacement of gypsum or anydrite; it is much less soluble than those minerals. It is usually formed by the selective removal of strontium ions from groundwater by reaction with deposits of calcium sulphate. Water containing a large proportion of calcium ions and a small proportion of strontium ions most commonly exists where limestone deposits occur in proximity. Celestite beds of appreciable thickness may be thus formed, particularly at the upper and lower boundaries of gypsum or anhydrite deposits. Such diagenetic formation of celestite is most favoured where there is appreciable flow of groundwater. Continuing diagenesis in a bicarbonate-rich environment may convert celestite to calciostrontianite (Salter and West, 1965). Smaller scale occurrences of celestite may be produced by a similar mechanism where gypsum veins have penetrated into limestone... Thus, there are many criteria for indicating the former presence of evaporites and it is wise to employ at least two. The occurrence of strontium minerals together with length-slow chalcedony [and/or lutecite] provides reliable evidence for the former presence of evaporites.'
West, I.M. 1974. Evaporite diagenesis in the Lower Purbeck Beds of Dorset. Reprinted in Kirkland and Evans (Ed.): Marine Evaporites, Origin, Diagenesis and Geochemistry. Benchmark Papers in Geology. [See West, 1964]
Abstract: Five stages have been determined in the diagenetic history of the calcium sulphate beds of Lower Purbeck age in Dorset, particularly by reference to abundant pseudomorphs and other relict textures and structures preserved in late-formed gypsum and in secondary silica and calcite. The weight of the overburden is thought to have controlled the changes. Occurrences are described of minerals, including celestite, calciostrontianite, lutecite and quartz remaining after the removal in solution of gypsum. A description is also given of secondary limestones which occur particularly in the Caps and Broken Beds. They are shown to be almost entirely replacements of original sulphate deposits.
West, I.M. 1975. Evaporites and associated sediments of the basal Purbeck Formation (Upper Jurassic) of Dorset. Proceedings of the Geologists' Association, London, 86, 205-225. By Ian Michael West of Southampton University. Abstract: Four facies of limestones, each with particular contents of calcitised evaporites and of skeletal debris were recognised. They are compared with sediments of modern evaporite-depositing environments. The lowermost limestones, stromatolitic and pelletoid with foraminifera, probably originated in intertidal to shallow subtidal, moderately hypersaline, water. Overlying pelletoid limestones with algal-mats and some gypsum are products of high-intertidal flats. The main evaporite beds were originally gypsum, probably formed in supratidal to intertidal, very hypersaline, palaeoenvironments. The gypsum was converted to anhydrite and later brecciated in part, forming the Broken Beds. Extensive calcitisation produced porous unfossiliferous limestones. Ostracodal limestones above probably originated in shallow, only moderately hypersaline water. All the basal Purbeck strata were formed in and around a large shallow gulf with extensive tidal flats and with water of varying but predominantly high salinities. At times of uplift, thin soils developed on the former margins of the gulf. Forests were able to exist there because, although the area was within the semi-arid zone, it was probably very near to the boundary of the warm-temperate zone. [End of Abstract.]
[Additional notes on topics discussed: Palaeosalinity origins of the basal Purbeck facies and lateral correlation. Mostly hypersaline to varying extents, including the stromatolite horizons. Fossil trees 'pickled' in a salt lake. Details of the basal Purbeck strata at all the main localities, studied petrographically. Depositional environments of the dirt beds and marls. Palaeoenvironmental significance of sedimentary cyles. Thickness variations of the facies. Relationship of the Broken Beds to the evaporitic facies. Local uplift. Penecontemporaneous fault movement. The Mupe Bay oil sand. Perryfield Quarry succession on the Isle of Portland.]
West, I.M. 1979. Sedimentary Environments and Diagenesis of Purbeck Strata (Upper Jurassic - Lower Cretaceous) of Dorset, U.K. Unpublished Ph.D. Thesis, Southampton University, 181 p. Abstract: Twelve papers, notes and a contribution to a book, all either published or accepted for publication, constitute this thesis. All parts of the classic, shallow-water, schizohaline Purbeck Formation of the type area are discussed but emphasis is on Lower Purbeck evaporites. Diagenesis of these involved much conversion of initial small lenticular crystals of gypsum to anhydrite with net-texture. The anhydrite was extensively replaced by calcite and celestite in the Broken Beds, a tectonic evaporite breccia at the base of the Purbecks. Evaporites were almost completely lost in solution from this breccia leaving characteristic relics of "vanished evaporites". Elsewhere, in the more argillaceous parts of the formation the sulphate remains, mainly as porphyrotopic secondary gypsum. Nodules and enterolithic veins are abundant in both the calcium sulphate and in the replacements. The similarity to those in Holocene sabkhas of the Trucial Coast (Shearman, 1966) suggested an origin on supratidal sabkhas, but there is a lack of desert sediments and instead the evaporites are interbedded with forest soils. Analogous Carboniferous evaporites show evidence of sabkha origins but no sign of desert conditions [West, Brandon and Smith, 1968. A tidal flat evaporitic facies in the Visean of Ireland. Journal of Sedimentary Petrology, 38, 1079-1093.]. New evidence has come from sabkhas in Northern Egypt where gypsum nodules develop in partly vegetated environment, dry but not excessively so, and supports other evidence for a semi-arid origin for the Lower Purbeck evaporites [West, Ali and Hilmy. 1979. Primary gypsum nodules in a modern sabkha on the Mediterranean coast of Egypt. Geology, 7, 354-358.]. The relatively dry climate was temporary and facies of higher parts of the Purbecks seem to result from sub-humid conditions. Throughout the formation lagoonal, 'intertidal' and supratidal deposits can be recognised but in the Middle and Upper Purbecks the lagoonal sediments have abundant brackish shelly faunas and, there, 'tidal-flat' deposits consist of shell-sand with dinosaur footprints but usually without evaporites. Progressively the proportion of land-derived clastics such as kaolinite and quartz sand increases as the continental Wealden is approached and final Purbeck sediments contain debris eroded from the underlying Portland Stone Formation, then uplifted at the western margin of the basin.
West, I.M. 1979. Review of evaporite diagenesis in the Purbeck Formation of Southern England. Symposium on: Sedimentation Jurassique W. European. ASF Publication Speciale, No. 1, 407-415.
West, I.M. and Hooper, M.J. 1969. Detrital Portland chert and limestone in the Upper Purbeck Beds at Friar Waddon, Dorset. Geological Magazine, 106, 277-280.
West, I.M., Shearman, D.J. and Pugh, M.E. 1969. Whitsun Field Meeting in the Weymouth Area, 1966. Proceedings of the Geologists' Association, 80, 331-340. [Portland, section of Perryfield Quarry etc]
Weymouth and Portland Borough Council, undated (about 1998). Portland: Geology and Landforms. Colour pamphlet. This is an illustrated colour pamphlet with maps and illustrations of the coast and of fossils from Portland. It also provides the following useful information: If you would like further information about Portland please contact: The Tourist Information Centre : 01305 -785747, or Weymouth and Portland Borough Council: Telephone 01305-761222, Email wpbc@weymouth.gov.uk.
Williams
, N. 1992. A Study of Landslides at the West Weare Cliffs, Portland, Dorset. B.Sc. Honours, Environmental Science Undergraduate Research Project, University of Southampton, 1992. By Nicola Williams. Summary: This report presents the results of a final year undergraduate research project on the landslides on the West Weare Cliffs of Portland, undertaken in 1991/92. A detailed field study of the landslides, their mechanisms and other degradation processes is presented together with their relationships to the geological, geomorphological and biological composition of the area. The study is augmented by published data and information gained from current leading authorities on the area. An estimate of recent coastal retreat is given and discussed together with predictions of the area of potential future movement. Evidence is presented to date the landslides using historical records, old photographs and maps of the area. (Supervised by Dr Ian West).
Williams, S. and Hardwick, P. 1996. Portland: Island of Discovery, a Teachers Guide. Weymouth and Portland Borough Council, Planning Department, North Quay, Weymouth, Dorset, DT4 8TA. Compiled and written by Simon Williams and Philip Hardwick of Weymouth and Portland Borough Council. ISBN 19000762005. (The reader may wish to enquire from the council as to whether there is a later edition available, as some aspects may become out-of-date.) This very useful publication consists of a substantial number of sheets (possibly about 200 or more ), with many maps, diagrams and photographs in a hard cover ring-binder and could be purchased for the sum of £22.50p.
Geography Fieldwork Enquiry - Contents:
Preface
Useful Local information: Information about the local area to assist in planning a visit, sources of information, services and facilities which may be required whilst on a Field Study Visit.
Attractions: Details of local attractions which are appropriate for school visits and which in some cases produce material for group visits and the National Curriculum.
Accommodation: Hotels and Guest Houses willing and able to accommodate field study visits, with a summary of services and facilities and details of current prices (this will be out-of-date in the 1996 edition).
Geography Fieldwork Enquiry Preface:
A key aim of the Project is to encourage visiting groups to stay, preferably on Portland, but if not in Weymouth and a schedule accommodation providers willing and able to accommodate field study groups is included within the guide. Some of the establishments may be prepared to offer free or reduced prices or similar offers for teachers involved in familiarisation visits to the area.
If you require any further information about this initiative, please contact: Simon Williams or Philip Hardwick in the Borough Council's Planning Department on 01305 206333 or 206214.
The Department is indebted to the assistance provided by Dorset County Council Geography Adviser and the following local geography teachers, particularly in working up the Case Study projects and who may be contacted if visiting teachers would like a local opinion on some of the projects which are included in this Guide:
Mike Hillary, Dorset County Council's Geography Education Adviser, Tel No. 01305 224698 Keith Bartlett, Royal Manor School Portland, Tel No. 01305 820262 Fax No. 01305 860417
Rhys Davy, Budmouth Technology College, Weymouth, Tel. 01305783057 Fax No. 01305 766389 Kelvin Huff, All Saints School, Wyke Regis, Weymouth, Tel. 01305 783391 Fax No. 01305 785291
Also acknowledged is the contribution by Colin Ellis and Eric Ricketts in respect of Case Study 8 and by Adrian Powell for the caricature sketches. Photographs are acknowledged in the text where appropriate.
Weymouth and Portland Borough Council Planning Department,
Wimbledon, W.A. and Cope, J.C.W. 1978. The ammonite faunas of the English Portland Beds and the zones of the Portlandian Stage. Journal of the Geological Society, 135, 183-190.
[END OF PORTLAND BIBLIOGRAPHY - UNDIVIDED SECTION - 1.1 - MAIN LISTING]
(NOT DIVIDED BY SUBJECT)
.
Allen
, T.D. 1863. Mammalian and human remains. Isle of Portland. Geologist, 6, 94, 136, 251.
.
Anonymous
, 1962. The Quarrying of Portland Stone. Reprinted from the Quarry Managers' Journal, June, 1962, 8 pp.
.
Arkell
, W.J. 1933. The Jurassic System in Great Britain. Clarendon Press, Oxford, 344p.
Attwooll
, M. 1989. Shipwrecks. Discover Dorset. The Dovecote Press, 79 pp. ISBN 1 874336 59 8.
.
Bastos
, A., Kenyon, N. and Collins, M. 2000. Symmetrical sand transport and deposition patterns associated with headlands: preliminary results. A poster at the Southampton Oceanography Centre (authors are at SOC). Abstract: Bathymetric, hydrodynamic and side scan sonar are being used to investigate the sediment processes associated with a headland - Isle of Portland (Pingree, 1978). However, first results show a fairly symmetrical distribution of bedforms, being apparently associated with net bedload transport patterns. Instead of residual circulation the transient nature of the flow during the tidal cycle (transient edies) should be controlling the bedload transport patterns and, as a consequence, the formation of the sedimentary deposits is related to the gradient in bottom stress. Some of the asymmetry of the morphology of the deposits is due to the greater influence of waves on the west side of the headland. This will lead to hypotheses that will have general application to coastal zone sediment transport. (data also provided to Dorset County Council)
Abstract:
The morphology and internal structure of sand shoals and sandbanks around a coastal headland (Portland Bill, southern UK) are described on the basis of sidescan sonar and high-resolution seismic data sets. Morphological and architectural evidence, combined with the spatial distribution and nature of the bedrock surface, indicates that the evolution of these deposits, especially the sandbanks, may not only be hydrodynamically controlled but also morphologically controlled. The internal structure of the sand shoals reveals a simple pattern of clinoforms dipping in the same direction as their steeper profile. In contrast, the internal structure of the sandbanks reveals that their lower seismic units consist of a sedimentary core interpreted as the remains of a lowstand deposit or an early stage of the bank development under different prevailing hydrodynamic conditions. The present morphology of the sandbanks is represented by upper seismic units characterized by large-scale sandwave foresets dipping at 6–8°. The nature and morphology of the bedrock surface may also influence the development of sandbanks in some cases. For example, to the west of Portland Bill, the morphology of the bedrock surface (basal reflector) restricts the development of the Portland Bank. This information may explain the asymmetric evolution of sandbanks around Portland Bill.
.
Blake
, J.F. 1880. On the Portland rocks of England. Quarterly Journal of the Geological Society, London, 36, 189-236. With notes and descriptions of Portland fossils and comparitive sections of the Portland rocks of England. By the Rev. J.F. Blake, M.A., F.G.S. Pp 190 -193 on the Isle of Portland [not highly detailed regarding the Isle of Portland but with information of Swindon, Vale of Wardour and elsewhere].
.
Bosence
, D.W.J. 1987. Mesozoic platform carbonates and benthic calcareous algae of the Severn and Wessex Basins. In: 4th International Symposium on Fossil Algae, Cardiff, July, 1987, edited by Robert Riding. Pre-Symposium Field Excursion, Excursions Guide, pages unnumbered. [See section: Portland and Purbeck Formations of the Isle of Portland. End-Jurassic regressive sequence with oncoids, oyster/Solenopora reefs, trees, palaeosols and tufas.]
.
Bruce
, P. 1989. Inshore along the Dorset Coast. First Edition, Boldre Marine, Lymington. 115p + charts. Paperback. By Peter Bruce. There was a second edition in 1996. [Useful for local names and coastal detail for the eastern Dorset coast. It has information on the Isle of Portland and tidal stream data for the area. Chapter 9, p. 82 et seq., is on Portland Harbour and the Fleet.]
.
Brunsden
, D., Coombe, K., Goudie, A.S. and Parker, A.G. 1996. The structural geomorphology of the Isle of Portland, southern England. Proceedings of the Geologists' Association, 107, 209-230. Authors' Abstract: The Isle of Portland, southern England, is composed of gently folded Upper Jurassic Beds ranging from the Kimmeridge Clay through the Portland Group to the Lower Purbeck Group which are gently folded to form part of the northern end of the Shambles Syncline. The essential arrangement of the beds is for hard, jointed well-bedded and permeable Purbeck and Portland limestones to overlie the Kimmeridge Clay members. The jointing along NW-SE, NE-SW, N-S and E-W master and conjugate sets closely parallels the axis of the syncline and the NNE-SSW fault pattern of the Purbeck Anticline and is a major regional landform control at all scales from the occurrence and form of individual rock falls to the shape of the island itself. Portland has a large number of landslips, which have been mapped from colour air photography. Their spatial pattern is spectacularly related to the geological conditions of the island and varies in size and type in a systematic manner as the thickness of clay and orientation of the dip changes with respect to coastline orientation. The slips, which occur predominantly in the winter months after heavy rainfall, are of frequent occurrence and pose major hazards to engineering structures. The landslide pattern and the overall morphology of the island is used to suggesta tentative model of landscape evolution which emphasizes the process of lateral spreading, loading, clay extrusion and erosional unloading. End of authors' abstract. [This is a key paper. Some further notes from the paper: Maps and dates of Portland landslips since 1615, including a major one on the East Weare in 1792. Seasonal distribution of slips - February, March. Joints. Coombe's joints. Development of a synclinal structure by extrusion of a ductile underlayer. Relation to Shambles syncline. No faulting.]
.
Buckland
, W.A. and De la Beche, H.T. 1836. On the geology of the neighbourhood of Weymouth and the adjacent parts of the coast of Dorsetshire. Transactions of the Geological Society of London, series 2, vol.4, pp. 1-46.
.
Bullen, R.A. 1894. Shells from the Portland rubble drift. Geological Magazine for 1894, p. 431. By the Rev. R.A. Bullen.
.
Clasby
, C.S. 2003. A Study of the Research Potential and Environment of Deposition of a Set of Dinosaur Footprints from Suckthumb Quarry on the Isle of Portland, Dorset. Unpublished undergraduate research project, School of Ocean and Earth Science, Southampton University, 56pp. Abstract: A number of slabs of rock bearing the footprints of dinosaurs, have been found in a quarry on the Isle of Portland, Dorset. The slabs originate in the middle part of the "Cypris" Freestones of the Purbeck Limestone Formation. The cast of the trackway has been preserved in the base of a large freestone unit and it is this which has been discovered. Petrological studies reveal considerable lateral variation of the bed. This and the subsequent difficulties in correlating the Purbeck strata of the Isle of Portland to that of the more easterly type section are discussed. The footprints were formed on the salt-encrusted surface of an ephemeral lake in an evaporitic environment, but with little evidence of product other than pseudomorphs after halite. Gypsum does not appear to be as common in this sequence as elsewhere in the succession and this is believed to reflect a non marine recharge system. Within these beds organic remains, mainly plant and insect, are locally abundant, though largely fragmented. Well preserved pollen and spores have also been recovered, and the results of their study confirm the variance of the western Purbeck. [This is a report by Caroline Clasby on her third year student project with one copy filed at Southampton University.]
.
Coombe
, E.D.K. 1982. Some Aspects of Coastal Landslips and Cliff-falls at Portland. Dissertation in the Bodleian Library, Oxford and the School of Geography, Oxford. This also exists, probably unchanged, in the form of an unpublished typescript for the Proceedings of Dorset Natural History and Archaeological Society, with 29 text-pages and 31 figures. The Dorset Proceedings version was not published because of its large size and dissertation format. By Mr. Ken Coombes of Exbourne, Wakeham, Portland, who at the time was a teacher of geography at Thornlow School, Weymouth. He received the Royal Geographical Society's annual award and Fellowship for this dissertation. [This is an extremely interesting account full of useful information on Portland and particularly on landslides. In particular it includes a map of joints on Portland. There is information on quarrying and history etc.]
Extract from the Introduction: As many geographers have pointed out, probably more has been written about the Dorset coast than about
any other comparable stretch of British coastline and it includes the Island of Portland as part of its appeal,
especially to the geomorphologist. Comparing the Dorset
coast with/the Hampshire Basin to the East, and that of
Devon to the west, one is faced with a coastline that is
intermediate in character as well as in position. From the Permian at Paignton eastwards to Portland Bill, the whole of Lyme Bay has been eroded in generally soft Triassic and Jurassic deposits. It would seem that virtually all traces of an older coastline have been removed since the last significant sea level rise, leaving only the platform and raised beach at Portland Bill extant.
It is probably true that the Island of Portland's preservation is largely unexplained, more so, perhaps, as there is now firm evidence of a sea-floor continuation of Portland strata planed off during some previous marine epoch affecting an area eastwards to Purbeck, and westwards into Lyme Bay (Donovan and Stride, 1961). Thus ,one may infer that the island of Portland probably stood up as an island hill on some interglacial marine platform, and may be analagous to the chalk Highdown Hill standing above the Sussex coastal plain today.
Arkell (1947) p.342, maintains that... "Portland came into existence as a headland 4 miles long since the middle of the Palaeolithic period or thereabouts..."
As Steers (1954) p.260 suggests that post-glacial sea level changes were rapid enough for peat to be preserved on the Dogger Bank, it seems possible, ceteris paribus, that the relatively hard Portland Stone would preserve traces of an older cliff line, possibly of more than one age and of..one level, along the Dorset 6Dast.
Because Portland is thus the. last vestige of the southern limb of the Weymouth anticline, it is unique not only as a relict landform, but also as an area for geomorphological study, especially of the effects of the Quaternary period. Portland has a relatively long coastline of some 15 kilometres under continuous wave attack encompassing an ever decreasing planimetric area currently of approximately 1160 hectares. Strahan (1898) p.114 quotes Dr. Fitton as maintaining...
"Few places, probably in the world, exhibit with such clearness, and in so small a space, phenomena of more extraordinary interest and of greater importance to theory..."
It has long been noticed that the cliff falls and landsli at Portland are a prominent and noteworthy feature of the is land topography. Observers as early as Leland (1546) and Hutchins (1710), and as recent as Perkins (1977), have historically and variously regarded them as resulting from earthquake, Acts of God, etc., and more recently as rotational slips, or topples due to structural weaknesses in the lithology combined with wave attack.
The presence of the adjacent Chesil Beach is evidence of the massive 7,000 mile fetch from the southwest, and implies high wave energy expended on the island (Plate No. 1). The raised beach at Portland Bill with its axis at 90 degrees to Chesil also implies a dominant fetch at a former higher sea level and from a different direction.
However important one regards marine erosion as a factor in the cliff falls, it is untrue to suggest that the sea has necessarily been a factor in all the slips on the island; but this adds greatly to the problems.
Arkell (1947) (op.cit., p.353) notes:
"The landslips round the cliffs of the northern
half of Portland are to some extent intermediate between normal cliff slides and inland slips, for some are ancient and date from the original formation of the escarpment, before the sea approached. Others are
very recent and are documented..."
It seems that little, if any, work has been published
to date giving clear definitive description of the falls and slips, and apparently none with evidence to explain the complex nature of the falls, which from the writer's investigation cannot be placed into anyone simple category, but raise more problems than they answer.
The vertical jointing running throughout the island has attracted much attention from geologists and others
during the past 120 years. For example, Gray (1861) p.129, noted:
"Fissures which traverse the island from NE to SW, and extend from within a few feet of the surface down to the clay. It would seem also, from the fact of the fissures being independent of any particular bed, that they were produced subsequent to the deposition of the most recent formation developed on the island. The direction of the fissures is so constant, that quarrymen profess to ascertain, very nearly the hour of the day by the extent of the shadow cast in the opening.." ... [continues].
.
Delair
, J.B. 1993. Reptilia from the Portland Stone (Upper Jurassic) of England: a preliminary survey of the material and the literature. Modern Geology, 18, 331-348. By Justin B. Delair, with contribution on the stratigraphy by William A. Wimbledon. Abstract: The Portland Stone has long been prime building material and, over the years, has yielded a diversity of vertebrate osteological and trace fossils. The literature and museum holdings of such fossils are surveyed and the distribution pattern of the reptiles is considered in terms of lithology and palaeoenvironments. Key words: Reptiles, crocodiles, Portlandian (Late Jurassic), England.
.
Damon, Robert,
Preface to Second Edition
Since the issue of the First Edition increased attention has been given to the Geology of the coast of Dorsetshire, especially in the contributions of Messrs. Blake and Hudleston, and Professor Prestwich, which in part have been embodied in the present volume.
Elementary and explanatory notes are given for the use of those young in the study of the science.
A description of the geological formations of Swanage and Bridport, the two extremes of the district under consideration, is for more convenient reference placed towards the end.
The Geological Survey of this district was almost entirely made by Mr. Henry W. Bristow, Senior Director of the Geological Survey of Great Britain. To him I am greatly indepted for a final revision of the work. Mr. W. Topley, of the Survey, has also kindly given much assistance, as have also Messrs. G. Sharman and E. T. Newton with the lists of fossils. Mr. Etheridge has favoured me with the Bridport portion of his unpublished sections of the Oolitic rocks of England.
The works I have consulted are necessarily very numerous, and to their respective authors I acknowledge my great obligations.
To the above and other friends, who have kindly responded to my enquiries for information, my sincere thanks are rendered.
R. Damon
Weymouth, October 1884.
.
Davies, K.H. and Keen, D.H. 1985. The age of Pleistocene marine deposits at Portland, Dorset. Proceeding of the Geologist's Association, 96 (3), 217-225.
.
Delair
, J.B. 1993. Reptilia from the Portland Stone (Upper Jurassic) of England: a preliminary survey of the material and the literature. Modern Geology, 18, 331-348. By Justin B. Delair, with contribution on the stratigraphy by William A. Wimbledon. Abstract: The Portland Stone has long been prime building material and, over the years, has yielded a diversity of vertebrate osteological and trace fossils. The literature and museum holdings of such fossils are surveyed and the distribution pattern of the reptiles is considered in terms of lithology and palaeoenvironments. Key words: Reptiles, crocodiles, Portlandian (Late Jurassic), England.
.
Donovan
, D.T. and Stride, A.H. 1961. An acoustic survey of the sea floor south of Dorset and its geological interpretation. Philosophical Transactions of the Royal Society, Series B, 244, 299-330.
.
Dorset County Council
, Devon County Council and the Dorset Coast Forum. 2000. Nomination of the Dorset and East Devon Coast for Inclusion in the World Heritage List. Published by Dorset County Council on behalf of Dorset County Council, Devon County Council and the Dorset Coast Forum. Publication of this nomination has been supported by English Nature and the Countryside Agency and has been advised by the Joint Nature Conservation Committee and the British Geological Survey. Design and production by Sillson Communications. 149pp. [Lavishly colour-illustrated account of the importance of Dorset geology, with superb aerial and other photographs and useful summary of Dorset geological information. Primarily designed to justify designating the Dorset coast as a World Heritage Site, it is an impressive production that is useful for reference or browsing.]
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Edmonds
, R., King, S., Badman, T. and Brunsden, D. 2002. The Jurassic Coast - 185 million years in 59 miles of coast. Geoscientist: the magazine of the Geological Society of London, vol. 12, no. 4, April 2002, pp. 4-7, with cover picture of a dinosaur footprint from the Pubeck Formation of Portland. By Richard Edmonds, Sally King, Tim Badman, World Heritage Team and Professor Denys Brunsden, Chairman of the Dorset Coast Forum (but the content page lists the article as by John Burland). Extract: "The Dorset and East Devon Coast became England's first Natural World Heritage Site in December 2001 after eight years of hard work and consultation by Dorset and Devon County Councils and the Dorset Coast Forum. Inclusion within the World Heritage List is an accolade of international significance but for the uninitiated it is probably quite taxing. Everyone can recognise that the Grand Canyon should be a World Heritage Site because it is so big. But the Devon and East Dorset Coast. Well, the answer lies in understanding the geology and its importance within a global concept... In summary, the coast between Exmouth in East Devon and Studland Bay in Dorset represents a near complete sequence of accessible and well researched rocks through the entire Mesozoic Era of geological time. In addition, the coast contains a number of internationally important fossil localities and displays a superb range of active geomorphological processes."
.
Edmunds
, F.H. and Schaffer, J. 1932. Portland Stone: its geology and properties as a building stone. Proceedings of the Geologists' Association, 43, 225-240.
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Ensom
, P. 1998. Discover Dorset: Geology. The Dovecote Press, Stanbridge, Wimborne, Dorset. 89 pp. ISBN 1-874336-52-0.
Dinosaur tracks from strata below the Cherty Freshwater Member, Lulworth Formation, Purbeck Limestone Group, of Dorset had not been recorded formally until 2002 when Professor Michael House published a preliminary note, in the Proceedings of the Dorset Natural History and Archaeological Society. He flagged the 2001 discovery of a number of blocks of the ‘Thick Slatt’, Hard Cockle Member, with casts of dinosaur tracks preserved on their lower surfaces, in a quarry on the Isle of Portland. New light is shed on the source of the tracks, and the history of their discovery is documented. The methods employed to record them are described. The traces are placed in their stratigraphic and palaeoenvironmental settings.
In this paper, how the tracks were made is described, and most importantly it is concluded that they are preserved as transmitted casts. Three distinct types of tridactyl track attributable to bipedal dinosaurs are recognized, as well as isolated tracks
which are interpreted as belonging to quadrupedal dinosaurs. Evidence is presented to support the interpretation that one of the tracks assigned to a quadrupedal dinosaur was produced by a sauropod. Despite their apparent differences, it is suggested that the majority of the tridactyl tracks were left by one species of dinosaur which was almost certainly herbivorous and lived in groups. One trackway may have been made by a carnivorous dinosaur.
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Falcon-Lang
, H.J. 1998. A Geological Survey of the Isle of Portland, Dorset. Undertaken by Dr H.J. Falcon-Lang, Department of Geology, Royal Holloway College, University of London, Egham, Surrey, TW20 0EX, UK for the Jurassic Coast Project, Dorset County Council, UK, October, 1998. 86 pages with maps, diagrams and photographs. [It provides much valuable information on the stratal successions in the various quarries on Portland.]
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Fitton
, W.H. 1836. Observations on some of the strata between the Chalk and the Oxford Oolites, in the south-east of England. Transactions of the Geological Society, London, 4, 103-389.
..
Francis - Dr Jane Francis of Leeds University. Notable specialist on Purbeck fossil trees and palaeosols, and also on Antarctic geology.
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Fursich
, F.T., Palmer, T.J. and Goodyear, K.L. 1994. Growth and distintegration of bivalve-dominated patch reefs in the Upper Jurassic of southern England. Palaeontology, vol. 37, Part 1, pp 131-171. By Franz T. Fursich, Timothy J. Palmer and Kay L. Goodyear.
Abstract: Patch reefs, up to 4 metres high and 8 metres across, grew amongst oolith shoals at the top of the Portland Limestone Formation (Portlandian, Upper Jurassic) on the Isle of Portland, southern England. Principal reef framebuilders, which provided between 55 and 70 per cent of the reef volume, were cementing bivalves, solenoporacean algae, and bryozoans. The remaining pore-space in the reef was filled by sediment, most of which is in the form of a precipitated peloidal cement. The cement lithified the reef while it was still exposed on the sea floor, and was probably precipitated under bacterial control. A diverse accessory fauna of small cementing encrusters and nestlers includes groups such as terebratulid brachiopods and lithistid sponges
-that have not previously been found in the Portland Limestone. Serpula (Cycloserpula) striatissima sp. novo and Carterochaena pulcherrima gen. et sp. novo are described. Both the primary organic framework of the reef and the submarine cements were bored by a variety of endoliths, which locally removed as much as 40 per cent of the reef volume. Vacated borings acted as sites for precipitation of further peloidal cement. Borings are well preserved as natural three-dimensional casts in cases where they originally perforated an aragonite substrate which has since dissolved. New taxa of borings consist of Cunctichnus probans ichnogen. et ichnosp. nov., Spirichnus spiralis ichnogen. et ichnosp. nov., Talpina bromleyi ichnosp. nov., and Entobia cervicornis ichnosp. novo.
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Goudie
, A. and Brunsden, D. 1997. Classic Landforms of the East Dorset Coast. Published by the Geographical Association in conjunction with the British Geomorphological Research Group. Sheffield. 48 pp. Series Editors - Rodney Castleden and Christopher Green. Low cost paperback , pocket size booklet. Concise with excellent colour illustrations including good aerial photographs. Sections comprise: Introduction, the Portland Cliff, the Portland Raised Beach, the south Dorset coast, the Lulworth Coast, the east Purbeck coast, Studland Bay and the South Haven Peninsula, Poole Harbour, Glossary, Bibliography. (see also companion volume on West Dorset).
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Harvey
, P.E.G. 900 Years in the Life of a Fortress Isle. Portland 900 years committee.
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Haslett
, S.K. 1992. Rhaxellid sponge microscleres from the Portlandian of Dorset, UK. Geological Journal, 27, 239-347. [These kidney-shaped sponge spicules are abundant features of the Portland Cherty Series. They were originally of opaline silica and have largely been replaced by calcite, thus providing a source of silica for the Portland chert. See also Wilson (1966)]
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Hayter, A. 2002. The Wreck of the Abergavenny: One of Britain's Greatest Maritime Disasters and its Links to Literary Genius. Macmillan, 223 pp. ISBN 0333 98917 1. By Alethea Hayter.
"In February 1805 The Earl of Abergavenny, one of the largest of the East India Company's ships set sail in convoy from Portsmouth for a voyage round the world to India and China. Her captain, John Wordsworth, was the younger brother of the poet William Wordsworth. On board were more than 400 passengers, troops and crew and a rich cargo of luxury goods and silver dollars. Only three days later, separated from the convoy by the stormy weather, the ship struck the notorious Shambles Shoal in Weymouth Bay and sank, drowning 260 souls including her captain."
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Hollings, D.F. 1993.
Welcome to the Home Page of the Village of Wyke Regis, Weymouth, Dorset, England. An excellent website written by D.F. Hollings, 36 Westhill Road, Wyke Regis, Dorset.
"Introducting Wyke Regis: Wyke Regis has a long and rich history with evidence of human occupation stretching back to the stoneage era some 10,000 years ago. The earliest written record relates to a charter signed by the Saxon King Ethelred 11 in 988 AD. The name Wyke Regis can be loosely translated as meaning "the farm of the King".
The present All Saints Church was consecrated in 1455 but there were at least two previous churches on the present site. Until the 1890's the people of Wyke earnt their living through farming and tishing. Farming records of the manor exist back to 1243 and tishing has taken place over many centuries off Chesil Beach in the turbulent waters of the English Channel.
In 1891 Robert Whitehead, the inventor of the deadly underwater torpedo, built his Whitehead Torpedo Manufactury at Ferrybridge, Wyke Regis and this resulted in engineering becoming the predominant occupation with a dramatic expansion in house building. Eventually Wyke Regis was absorbed into the much larger Borough of Weymouth and Portland but it still retains its own distinctive character."
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Hounsell
, S.S.B. 1952. Portland and its stone. Mine and Quarry Engineering, 18, 107-114.
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House
, M.R. The late Professor Michael House, author of well-known guides to the geology of the Dorset Coast, and former Professor of Geology at Hull University and at Southampton University. He was most notable as a Devonian specialist but was much involved in research and publication on the Jurassic and Cretaceous of the Dorset coast, his home region.
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Howe
, J.A. 1910. The Geology of Building Stones. Edward Arnold, London. 455 pp.
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Hunt
, C.O. 1985. Miospores from the Portland Stone Formation and the lower part of the Purbeck Formation (Upper Jurassic/Lower Cretaceous) from Dorset, England. Pollen et Spores, 28, nos. 3-4, 419-451.
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Jarzembowski
, E.A. 1995. Early Cretaceous insect faunas and palaeoenvironment. Cretaceous Research, 16, 681-694. [Notes: Warmer conditions are indicated by many species of Blattoidea. Lepidoptera were beginning at this time.]
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Kemp
, J.P. undated. The Book of Weymouth and Portland. By John Kemp; drawings by McLean. ISBN 0 907683 32 0. Nigel J. Clarke Publications, 3 Russel House, Lyme Close, Lyme Regis, Dorset. 54pp. [Small paperback booklet. With the following pictures: p. 24 Smallmouth Ferry before 1839 with rope and horses; p. 50 of Portland Ferry House, 1800.]
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Legg
, R. 1976. Portland Souvenir Magazine. Portland Branch of the Royal Naval Association. 22 pp.
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Lilley
, G. 1892. Tourist's Guide to the Isle of Portland.
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Mackenzie
, R. 1993. Portland: A Topographical and Historical Gazetteer. Published by K.D. Print. Revised August, 1995. (Small paperback book, pages unnumbered. Price £2 - 40 p. in 1998)
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May
, V. 2005 (?). Coastal Form Processes. Part of: Physical Changes to the Coast. Webpage:
Coastal Form Processes . By Professor Vincent May of Bournemouth University. Part of Dorset Coast Digital Archive - Dorset Coast Digital Archive, operated by Bournemouth University, Bournemouth Borough Council, Dorset County Council and Dorset County Museum. [A very good website with specific data. Recommended.]
Introduction
General Information
Detailed Information
Waves
Tides
Sea Level Rise
Coastal Erosion
Beaches
Dunes and Estuaries
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Milner
, A.R. and Batten, D.J. (Editors) 2002. Life and environments in Purbeck times. Special Papers in Palaeontology, No. 68, Palaeontological Association, London, 268pp. Report from a symposium on the Purbeck Formation at the Dorset County Museum, Dorchester, Dorset, March 19-22, 1999. Contains 16 papers and with a preface. Dedicated to the memory of the late Professor Michael House. Price £66. Published December 2002. With 22 plates, 7 tables and 77 text-figures.
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Mitchell
, V. and Smith, K. 1989. Branch Lines Around Weymouth; from Abbotsbury, Easton and the Quay. Middleton Press, Easebourne Lane, Midhurst, West Sussex, GU29 9AZ. ISBN 0 906520 65 7. 96pp. Price was £8.95p. [This railway book contains several old maps and charts of Portland including parts of the Chesil Beach. These include the 1867 chart of the northern Portland, the Chesil Beach and Weymouth (showing the originally very narrow, Small Mouth), a 1903 map of the Mere and adjacent Chesil Beach, a 1929 large scale map of Ferrybridge showing Small Mouth as it originally was. It also has photographs of the Fleet Viaduct at Ferry Bridge etc. The maps and photographs of the Easton and Church Hope Railway are of interest regarding the east cliffs of Portland and their landslides. There is also much information on former quarries on the old maps.]
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Morris
, S. 1892. Portland Place Names.
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Palmer
, S. 1970a. The Stone Age industries of the Isle of Portland, Dorset, and the utilization of Portland chert as artifact material in southern England. Proceedings of the Prehistoric Society, 36, 82-115.
Summary: Artefacts of a Late Palaeolithic aspect have in the past been recorded from various sites on the Island of Portland, but have never previously been found and studied in a late Pleistocene context without a substantial admixture of later lithic material. Limited excavation of a site in the north of the island recently produced a sizeable assemblage with some interesting but atypical characteristics, reminiscent of finds made nearby at the end of the 19th century. [There is reference to Damon's (1884) description of a midden on the southwest glacis of the Verne, adjacent to the road to Fortuneswell.]
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Abstract: Patch reefs, up to 4 metres high and 8 metres across, grew amongst oolith shoals at the top of the Portland Limestone Formation (Portlandian, Upper Jurassic) on the Isle of Portland, southern England. Principal reef framebuilders, which provided between 55 and 70 per cent of the reef volume, were cementing bivalves, solenoporacean algae, and bryozoans. The remaining pore-space in the reef was filled by sediment, most of which is in the form of a precipitated peloidal cement. The cement lithified the reef while it was still exposed on the sea floor, and was probably precipitated under bacterial control. A diverse accessory fauna of small cementing encrusters and nestlers includes groups such as terebratulid brachiopods and lithistid sponges
-that have not previously been found in the Portland Limestone. Serpula (Cycloserpula) striatissima sp. novo and Carterochaena pulcherrima gen. et sp. novo are described. Both the primary organic framework of the reef and the submarine cements were bored by a variety of endoliths, which locally removed as much as 40 per cent of the reef volume. Vacated borings acted as sites for precipitation of further peloidal cement. Borings are well preserved as natural three-dimensional casts in cases where they originally perforated an aragonite substrate which has since dissolved. New taxa of borings consist of Cunctichnus probans ichnogen. et ichnosp. nov., Spirichnus spiralis ichnogen. et ichnosp. nov., Talpina bromleyi ichnosp. nov., and Entobia cervicornis ichnosp. novo.
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Perkins
, J.W. 1977. Geology Explained in Dorset. David and Charles, Newton Abbott, 224 pp. ISBN 0-7153-7319-6. [A good simple explanation of Dorset geology with well-labelled diagrams.]
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Perry
, C.T. 1994. Fresh-water tufa stromatolites in the basal Purbeck Formation (Upper Jurassic), Isle-of-Portland, Dorset. Geological Journal, 29, 119-135. Abstract: Recent interpretations of the tufaceous limestones from within the 'Caps Beds' on the Isle of Portland have suggested a depositional environment of intertidal flats and lagoons with typically higher than normal marine salinity levels, a stark contrast with earlier ideas of a freshwater origin. However, evidence is presented in this paper to show that these deposits are indeed most likely to be freshwater in origin. The micro-fabrics observed are typical of those seen in freshwater tufas forming at the present day, and contrast with those observed within intertidal/subtidal stromatolites. Furthermore, the Portland deposits lack syndepositional evaporite deposits, they lack recognizable intertidal deposits, and any lagoonal sediments observed are depositionally distinct from the tufas. Finally, the soil horizons observed are clear evidence of periodic subaerial exposure and isolation from marine influences. Four facies types are identified on Portland: (1) tufaceous limestone; (2) littoral grainstones; (3) subaerial stromatolites; and (4)
paleosols. Each facies is repeated a number of times through the sequence, and evidence is presented to show that these formed in a marginal marine setting as a response to a series of minor transgressive (soils to freshwater lakes/lagoon to saline marine/lagoonal) and regressive events (saline marine/lagoonal to soils). The tufa stromatolite deposits themselves, which are often developed around cylindrical holes (representing former tree trunks and branches), are shown to have developed seasonally, by the precipitation of carbonate, due to microbial activity within the freshwater lake environment. Precipitation appears to have been most intense around tree bases (and any associated vegetation), where an active biofilm developed on the underlying soil substrate. Two distinct textures are recognized in this material: (1) micro-porous and (2) macro-porous. These developed together in a crudely laminated, semi-concentric pattern around the holes and together may represent a seasons growth of tufa. [This paper is particularly useful in providing detailed description and showing the unusual features of the Purbeck stromatolites. The present writer considers that the lack of a freshwater gastropod fauna, lack of low salinity ostracods, and the presence of pseudomorphs after gypsum in the equivalent strata (the Hard Cap) with stromatolites at the Fossil Forest is evidence against a freshwater origin. See West (1975) for details of high salinity evidence. ]
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Pingree
, R.D. 1978. The formation of the Shambles and other banks by tidal stirring of the seas. Journal of Marine Biological Association, UK..
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Pugh
, M.E. 1968. Algae from the Lower Purbeck Limestones of Dorset. Proceedings of the Geologists' Association, 79, 513-523, pl. 13-18.
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Quest
, M. 1985. Petrographic and Geochemical Studies of the Portland and Purbeck Beds of Dorset. Unpublished Ph.D. Thesis, Department of Geological Sciences, Faculty of Science and Engineering, University of Birmingham, England, 347pp. By Martin Quest. Supervised by Professor Tony Hallam; thesis examined by Ian West. Synopsis: The Portland and Purbeck Beds (Upper Jurassic - Lower Cretaceous) exposed along the south Dorset coast are examined using a variety of geochemical and petrographic tools in an attempt to elicit diagenetic and palaeosalinity information. Boron in the less than 2 micron illite/total clay correlates well with inferred salinity in the Purbeck and there are important conclusions to be drawn regarding element re-cycling. In the Portland Limestone Formation there is no correlation with salinity, the very low boron concentrations possibly reflecting syn-depositional illite degradation. In the Portland Sand Formation and top-most Kimmeridge the concentration of boron (greater than 250 ppm.) is too high for the inferred marine salinities and probably reflects a mineralogical boron input in the form of glauconite. Petrographic, stable isotope and minor/trace element analysis of the Portland Limestone Formation confirms a very simple diagenetic history compatible with early lithification in the shallow sub-surface meteoric zone. A positive correlation between del 18 O and Sr/Na suggests increased diagenetic stabilisation of carbonates on the swell and eastern basin compared to those in the western basin. An apparent isotope and elemental cyclicity on the Isle of Portland may correspond to variations in eustatic sea level. Isotopic analysis of the Purbeck type-section at Durlston Bay has failed to differentiate between early and late-cemented carbonates. This is probably the result of late (ferroan) cements in the former imparting heavy del 13 C signature. Stable isotope and petrographic work on Middle Purbeck beef has identified a burial diagenetic origin. Petrographic, stable isotope, trace element and XRD work on the dolomites of the Portland Sand Formation rejects a penecontemporaneous origin and suggests that they were formed by the dolomitization of a stabilised (lithified?) low Mg calcite mud. Mg was supplied via evaporatively modified solutions, dolomite formation taking place in a partially isolated diagenetic system. The timing of dolomitization is unclear although there is some evidence that it occurred during a period of low eustatic sea level prior to deposition of the Portland Limestone Formation. In the extreme east of the region, basal Purbeck calcitised evaporites exhibit extreme del 13 C depletion (del 13 C - 25 %) suggesting an origin via bacterial sulphate reduction. Calculations using minor/trace element data indicates that calcitisation occurred within a partially closed environment. The absence of very light carbon values further west may reflect less severe reduction reactions or inorganic calcitisation in an aerobic zone associated with a structural high. End of abstract. [This is a very interesting thesis containing good work which has not been published and is therefore not well-known. The isotopic and other geochemical work in general supports previous petrographic studies. Note the two types of calcitisation in the Broken Beds and top Soft Cap which accord with petrographic evidence. There is much calcitised anhydrite in the east and calcitised gypsum in the west. The bacterial reduction theory brings up the interesting topic of hydrocarbons having once been present in the Broken Beds in certain areas, and this is quite likely. The Portland dolomitisation theory differs from that of Townson (1975) who regarded it as penecontemporaneous.]
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Radley
, J.D. 2002. Distribution and palaeoenvironmental significance of molluscs in the Late Jurassic - Early Cretaceous Purbeck Formation of Dorset, southern England: a review. Pp. 41-51 in: Milner, A.R. and Batten, D.J. (Editors) 2002. Life and environments in Purbeck times. Special Papers in Palaeontology, No. 68, Palaeontological Association, London, 268pp. Report from a symposium on the Purbeck Formation at the Dorset County Museum, Dorchester, Dorset, March 19-22, 1999. By Jonathon D. Radley, University of Portsmouth and Warwickshire Museum. Abstract: Knowledge of the stratigraphic distribution of Purbeck molluscs in the largely lacustrine to marginal marine Purbeck Formation of Dorset, southern England is summarised. The gastropod faunas are well known but the bivalves await detailed documentation. The shell concentrations are largely a result of wave and/or current processes although bivalves are preserved in life position. Comparision with Recent marginal-marine settings suggests that the stratigraphic distribution of Purbeck molluscs reflects long-term palaeoenvironmental change. Some bivalves are interpreted as strongly euryhaline, environmentally-tolerant opportunists. Others, notably those of marine aspect, probably tolerated only restricted salinity fluctuations. Dinosaur tracks throughout much of the succession indicate no significant change in water depth. Hence salinity excursions are attributed mainly to fluctuations in runoff and evaporation, as well as changing barrier porosities and inflow-channel configurations. Amongst the near-marine phases, the Cinder Member provides evidence for attendant sea-level rise. Many upper Middle-Upper Purbeck shell concentrations resemble those of the younger Wealden lacustrine-lagoonal successions and attest to upfaulting or intrabasinal highs and/or of the Cornubian massif in latest Berriasian or ealiest Valanginian times. [This paper includes a valuable listing of mollusc species from the various members of the formation and some of these occurrences are not well-known. Radley discusses some of the shell beds: "The concordant biofabrics of the shell pavements and thinner bioclastic limestones indicate oscillatory flow as the dominant mechanism (Kidwell and Bosence, 1991). This is confirmed by imbricated, stacked and nested shell amongst the densely packed accumulations... The Purbeck shell concentrations reflect varying degrees of time-averaging and environmental condensation... Clements (1973) recognised open, closed and transitional salinity series in the Purbeck Formation of Dorset through his studies of the ostracods. Thus the Lower Purbeck Beds are largely 'closed' above the basal strata. Consistently the sedimentological data (West, 1975) indicate a hot, semi-arid, sometimes hypersaline, coastal-lagoonal setting with limited marine influence. This interpretation is supported by the molluscan faunas which comprise low salinity and high salinity assemblages with no intervening influxes of marine taxa...The Middle and Upper Purbeck Beds signify largely 'open' environments (Clements, 1973). Accordingly their molluscan associations indicate salinities within the freshwater-euhaline range. Replaced evaporites are mostly restricted to the 'closed' lacustrine Cherty Freshwater Member.. An outline representation of the broad-scale, member-level salinity changes based on molluscan assemblages is presented in text-fig 1." -- There is much more of interest and the diagram referred to is particularly useful. I thoroughly agree with the contents and recommend this paper! - IMW]. [Portland significance - Lower Purbeck strata present on Portland contain Protocardia purbeckensis and other molluscs.]
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Rohling
, E.J., Grant, K., Hemleben, CH., Siddall, M., Hoogakker, B.A.A., Bolshaw, M. and Kucera, M. 2008. High rates of sea-level rise during the last
interglacial period. Nature Geoscience, vol. 11, January 2008, pp. 38-?. Published online: 16 December 2007.
The last interglacial period, Marine Isotope Stage (MIS) 5e, was characterized by global mean surface temperatures that were at least 2 degrees C warmer than present. Mean sea level stood 4–6m higher than modern sea level, with an important contribution from a reduction of the Greenland ice sheet1. Although some fossil reef data indicate sea-level fluctuations of up to 10m
around the mean, so far it has not been possible to constrain the duration and rates of change of these shorter-term variations. Here, we use a combination of a continuous high-resolution sea level record, based on the stable oxygen isotopes of planktonic foraminifera from the central Red Sea, and age constraints from coral data to estimate rates of sea-level change during
MIS-5e. We find average rates of sea-level rise of 1.6m per century. As global mean temperatures during MIS-5e were comparable to projections for future climate change under the influence
of anthropogenic greenhouse-gas emissions, these observed rates of sea-level change inform the ongoing debate about high versus low rates of sea-level rise in the coming century. [continues]
[this is relevant to the Portland Raised Beaches]
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Ross
, A.J. and Vannier, J. 2002. Crustacea (excluding Ostracoda) and Chelicerata of the Purbeck Limestone Group, southern England: a review. Pp. 71-82 in: Milner, A.R. and Batten, D.J. (Editors) 2002. Life and environments in Purbeck times. Special Papers in Palaeontology, No. 68, Palaeontological Association, London, 268pp. Report from a symposium on the Purbeck Formation at the Dorset County Museum, Dorchester, Dorset, March 19-22, 1999.
By Andrew Ross, The Natural History Museum, London and Jean Vannier, Universite Claude Bernard Lyon 1, Villeurbanne, France. Abstract: Three orders of Crustacea, apart from the Ostracoda, are represented in the Purbeck Limestone Group of southern England: the Isopoda, Conchostraca and Decapoda. Two species of isopod have been recorded: Archaeoniscus brodiei Milne Edwards and a single specimen of Cyclosphaeroma woodwardi Van Straelen. However, examination of the specimen of C. woodwardi has shown that it is from the Portland Group and not from the Purbeck Limestone Group. Archaeoniscus brodiei is abundant at one horizon just above the Cinder Bed in the Vale of Wardour, Wiltshire, which Brodie called the Isopod Limestone. Four species of conchostracans have been recorded: Liograpta subquadrata (J. de C. Sowerby); L. jurassica Novozhilov; Brachygraptus wardourensis Novozhilov; and Pseudograpta andrewsii (Jones). The order Decapoda is represented by two unidentified species belonging to the families Erymidae and Coleiidae. One chelicerate specimen is known, belonging to the subclass Xiphosuria. Associated ostracods indicate that it came from the base of the Purbeck Limestone Group or the Portland Group. It is identified as Mesolimulus sp. and constitutes the second xiphosuran record for the Mesozoic of the UK.
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SCOPAC (Standing Conference on Problems associated with the Coastline). 2004. Isle of Portland and Weymouth Bay (Portland Bill to Redcliff Point).
Available online at:
SCOPAC - Isle of Portland and Weymouth Bay.
Weymouth Bay is one of only three open coast frontages in the SCOPAC region with an east-facing orientation. It cuts across a succession of Jurassic strata related to the disposition of the Weymouth anticline, the only surviving part of the southern limb being represented by the "Isle" of Portland extending southward to form the major headland of Portland Bill - see Photo 1 (Bird, 1995; Brunsden and Goudie, 1997). The Bay itself comprises the inundated and partly eroded remains of the Wey river valley occupied by a barrier beach of gravel and sand which was formed by the landward migration of sediments that were combed up during Holocene sea level rise. Cliff erosion occurring between Ringstead Bay and Redcliff Point provided an additional local source of material for the barrier, with material being transported westwards along a locally reversed drift pathway prior to the emergence of Redcliff Point (Photo 2) as a transport boundary. The barrier enclosed a small estuary and drift deflected its entrance westward against the hard Nothe headland (Photo 3). The estuary is now largely infilled by sedimentation and is occupied by the Yacht basin and Radipole Lake. Major complex landslides occur in areas of high topography on the north of the Isle of Portland where resistant and/or porous cap rocks overlie soft impermeable clays (Photo 4)... [continues]
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Seward
, A.C. 1897. Cycadeoidea gigantea, Seward: an omission. Geological Magazine for 1897, p. 190.
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Strahan
, A. 1898. The Geology of the Isle of Purbeck and Weymouth. Memoirs of the Geological Survey, England and Wales. London. 278pp. Published by Order of the Lords Commissioners and Her Majesty's Treasury. Price 10 shillings and 6 pence. Printed for Her Majesty's Stationery Office, by Wyman and Sons, Limited, Fetter Lane, EC. With coloured map, cross-sections and a bibliography of books, papers and maps by W. Whitaker, F.R.S. (1761-1873) and by A. Strahan, M.A. (1874-1898).
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Thomas
, J. and Ensom, P. 1989. Bibliography and Index of Dorset Geology. Dorset Natural History and Archaeological Society. 102 pp. [Valuable guide to Dorset geological literature including journal articles, newspaper reports and obscure publications.] See also the internet version - Bibliography and Index of Dorset Geology.
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Trim
, P. 1991. The quarrying of Portland Stone. Isle of Portland Heritage Trust. 21pp + map.
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Underhill
, J.R. 2002. Evidence for structural controls on the deposition of the late Jurassic- early Cretaceous Purbeck Limestone Group, Dorset, southern England. Pp. 21-40 in: Milner, A.R. and Batten, D.J. (Editors) 2002. Life and environments in Purbeck times. Special Papers in Palaeontology, No. 68, Palaeontological Association, London, 268pp. Abstract: Integration of field studies with subsurface data demonstrate that deposition of the late Jurassic - early Cretaceous Purbeck Limestone Group occurred under semi-arid conditions during an important phase of syntectonic extensional activity in the Wessex Basin. Use of structural restorations and neotectonic analogue studies support the introduction of a new model to account for the regional and local along-strike variability in deposition of the Purbeck Limestone Group. It is proposed that the segmented nature of the episodically-active, basin-bounding Purbeck Fault explains observed thickness and sedimentological variations, including lateral facies changes and clast reworking. In addition to affording a tectonic framework in which to understand the rich palaeontological assemblages, the new depositional model also provides a mechanism for explaining the rapid death and unusual preservation of conifer forests through rapid submergence following co-seismic activity on the normal fault system. [By John R. Underhill, Department of Geology and Geophysics, University of Edinburgh.]
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Wallis, 1891. The Portland stone quarries. Proceedings of the Dorset Field Club, vol. 12, p. 187.
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Walshaw
, G. 1993. An Environmental Study of the Eastern Cliffs of the Isle of Portland, Dorset. B.Sc. Hons. Environmental Science Project, University of Southampton, 1993. By Genevieve Walshaw. 32 pp + appendices, maps and diagrams. Abstract: The following report presents the findings of a third year undergraduate research project on the eastern cliffs of the Island of Portland, Dorset, completed in 1992-1993. The study involved detailed mapping of the landslide units and their mechanisms, the geomorphology of the area and the biological communities present. Geological and biological cross sections of the site have been drawn and analysed for relationships. The degradation processes on the eastern coast of the Isle of Portland consist of a combination of topples and rotational slides. Rotational slides are dominant in the north and topples are dominant in the south. Trends in plant communities exist as a result of the geomorphology that the cliff falls create.
[This was a First-Class Honours standard undergraduate project and it contains much useful information.]
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Waring
, E. 1967. The black dog in Dorset. Proceedings of the Dorset Natural History and Archaeological Society for 1966, vol. 88, 234-235. [record of Dorset folklore]
"There are two type of phantom dog in English Folklore...
7. Portland. The Row Dog ("row" rhymes with "cow") was a shaggy black dog "as high as a man", with fiery eyes "as big as tea-saucers". It was unwise to go out when he was about: he didn't attack you, but barred your way. His route is given variously as from Grove Point to the Bill, from the end of Wakeham to Perryfield Corner, and along Avalanche Road. In addition to the above Tophill sites, the dog is also known at Underhill...
From the evidence of items 1, 2, 3, 5, 6 and 7 above, it would seem safe to generalise and say that the Black Dog is known along the West Dorset coast from Lyme Regis to Portland. There are some signs in the region of the Stour, but no trace of him, to my knowledge, in the Frome Valley or Purbeck."
.
Warren
, J.W. (year not yet known to me). The Island and Royal Manor of Portland. By order of the Court Leet and Court of the Manor.
.
Weymouth and Portland Borough Council
. 1997. Portland Circular Walks. Pamphlet. With useful maps and notes.
.
White
, E. and White, C.J. Old Portland : the eighteenth and nineteenth century memoirs of Elizabeth Pearce (later White) and Clara Jane White (later King Warry) of Portland Isle, Dorset.
.
Williams
, N. 1992. A Study of the Landslides at the West Weare Cliff, Portland, Dorset. Unpublished Undergraduate Environmental Science Project for B.Sc. University of Southampton, 64pp + Tables, Figures and Appendices. Abstract: This report presents the results of a final year undergraduate research project on the landslides on the West Weare Cliffs of Portland, Dorset, undertaken in 1991/92.A detailed field study of the landslides, their mechanisms and other degradation processes is presented together with their relationship to the geological, geomorphological and biological composition of the area. The study is augmented by published data and information gained from current leading authorities on the area. An estimate of recent coastline retreat is given and discussed together with predictions of the areas of potential future movement.
Evidence is presented to date the landslides using historical records, old photographs and maps of the area.
[This is an unusually good student project, of First Class Honours standard, with much interesting information.]
.
Wimbledon, W.A. 1976. The Portland Beds of Wiltshire. Wiltshire Archaeological and Natural History Magazine, 71, 3-11.
Abstract: On the basis of new and large collections of ammonites, a succession of ammonite faunas is described from the Portland Beds of southern England and a revised scheme of Standard Zones (=chronozones) proposed. The faunas of the Portland Freestone of Dorset are shown to consist largely of hitherto undescribed species; Titanites anguiformis sp. novo is described and figured therefrom. Correlations are proposed with other areas where the Portland Beds occur, and the scheme is integrated with the zonal scheme proposed by Casey (1974) for the younger Portlandian faunas. Glaucolithites glaucolithus Buckman and Titanites giganteus (Sowerby) are redefined with the aid of new material. 'Portlandian' is preferred as stage name for the terminal Jurassic stage. [end of abstract]
The first scheme of zones for the Portlandian Stage of the Upper Jurassic was proposed by Salfeld (1913) but has suffered because some of the index species used were of dubious interpretation, and it was based on sections in the S Midlands now known to be incomplete. Salfeld's zonal table was succeeded by Buckman's hemeral scheme. Buckman was the first person to attempt any really detailed stratigraphical work on the Portland Beds, and he obtained, from quarries in the Thame district ammonites which were described half a century ago in 'Type Ammonites' under a multiplicity of new generic and specific names. Although Buckman's hemeral scheme has long since been abandoned, his work is a very useful record of the faunal succession in an area where there are now few exposures. Comparison with sections further south has shown that his records are essentially correct as far as recording of horizons is concerned. Where his work failed, and also that of subsequent workers, was in the correlation of the south Midland successions with those of the Dorset coast. This was due to the persistent acceptance of certain widespread misconceptions concerning the ammonites and their stratigraphic relationships, a lack of systematic collecting, and a consequent inability to establish the ranges of the faunal assemblages.
Recent work on the Portland Beds throughout their outcrop by the authors, but with emphasis on the presumed complete successions in Dorset, has shown how wrong some of the former correlations were, and although work has not yet reached completion (when a joint monogtaphic work is contemplated) sufficient is now known to set up a revised zonal scheme.
The work on the faunas of the Portland Stone, the subjacent rocks north of Dorset, and the systematic palaeontology, is by Wimbledon. This has been integrated with Cope's work on the Portland Sand in Dorset.
The Faunal succession
A succession of distinctive ammonite faunas has been recognised throughout the Portland Beds (Fig. 1). In ascending stratigraphical order these are:
Fauna 1: Progalbanites-Epivirgatites fauna
The genus Progalbanites Spath 1933 appears to be quite distinct from the earlier Volgian genus Zaraiskites with which it has long been confused (see Casey 1967, p. 132). The type species of the genus, P. albani, is frequently common, and is associated with hitherto undescribed species of the genus. The remainder of the ammonite fauna includes species of Epivirgatites including E. nikitini (Mich.), E. vulgaris (Spath) and others. There are also undescribed species of Pavlovia. Amongst the pavloviids are occasional fragments of forms apparently close to the subgenus Epipallasiceras Spath (see Buckman 1926, pI. 693).
[continues for 10 pages, including three large photographic plates of ammonites.
.
Webster
, T. 1826. Observations on the Purbeck and Portland Beds. Transactions of the Geological Society of London, Series 2, 37-44.
.
West
, I.M. 1960. On the occurrence of celestine on the Caps and Broken Beds at Durlston Head, Dorset. Proceedings of the Geologists' Association, 71, 391-401. Abstract: An occurrence of celestine in the Lower Purbeck Beds at Durlston Head is described and shown to be of syngenetic origin. Deposition probably took place near the margin of a basin of evaporite deposits into which strontium solutions were introduced. At a later date the celestine has been involved both in the brecciation that formed the Broken Beds and in complex local faulting. [This record of strontium minerals was the first definate evidence of former evaporites in the Broken Beds. It supported the hypothesis of Hollingworth (1938) that gypsum or anhydrite were once present at this horizon. The precise origin of the celestite, however, was not well-understood at that time, and it was later shown to be a replacement of evaporites (connected with groundwater flow up the fault-plane) and not syngenetic. See West (1973; 1975). The cliff section (fig. 2) is of a downbulge into former evaporites, and is a relatively complex part of the Durlston Bay cliffs that is not easily interpreted at first sight. Two celestite horizons are present, but the palaeosols of the Lulworth area are not properly developed here because this locality is in the "basinal" facies of the Purbecks. Since this paper was written celestite has been found in the Purbecks in the Soft Cockle Member of Durlston Bay and the Isle of Portland, in the Caps and Broken Beds at Worbarrow Tout and at Stair Hole. Calciostrontianite also occurs at Durlston Head (Salter and West, 1965).]
.
Weymouth and Portland District Council
. (date unknown - about 2001). Portland Fieldwork Guide (10 Case Studies). In 2001 - £15 per copy, plus £3 p&p. Also Supplementary Case Studies: 11. Portland Coastal Footpath, 12. Resort Tourism, 13. Portland Bill Visitor Centre, 14. Coast Geology and Landslips, 15. Prison Ship Portland, 16. River Wey Valley. (Mostly either £3 or £4 each in 2001, plus £1.50 p&p. Available from Weymouth and Portland Borough Council, North Quay, Weymouth, Dorset, DT4 8TA.
.
Wilkinson
, I.P. 2007. The distribution of Late Kimmeridgian and Portlandian ostracoda in southern England. La répartition des ostracodes du Kimméridgien supérieur au Portlandien en Angleterre méridionale
Revue de Micropaleontologie. By Ian P. Wilkinson, British Geological Survey, Keyworth, Available online 1 October 2007.
Abstract: The vertical distribution of ostracods in the Upper Kimmeridgian and Portlandian (sensu anglico) succession in three cored boreholes at Hartwell, Tisbury and Fairlight, are compared to other successions in southern England. The Upper Kimmeridge Clay Formation yields rich, but low diversity ostracod faunas, characterised by stratigraphically restricted species of Aaleniella, Galliaecytheridea, Klentnicella, Macrodentina, Mandelstamia, Micrommatocythere, Paralesleya and Prohutsonia. Several continue into the Portlandian, but some species, belonging to genera such as Cytherelloidea, Paracypris, Fabanella, Galliaecytheridea, Klieana, Paraschuleridea, Eocytheridea, Paranotacythere, Procytheropteron, Rectocythere and Macrodentina, appear for the first time. Biostratigraphical subdivision is made difficult by provincialism caused by decreasing salinities and facies change during the Late Portlandian. Marine taxa such as Protocythere, Macrocypris, Paraschuleridea, Paranotacythere, Procytheropteron and Rectocythere were replaced by euryhaline forms, such as species of Fabanella and Mantelliana, and fresh-oligohaline species of the genera Cypridea, Scabriculocypris, Alicenula and Rhinocypris.
.
Will
, J. 2003. The Sedimentology and Palaeoenvironments of the Purbeck Formation of the West Coast of Portland. 42pp. Unpublished B.Sc. undergraduate research project, 2002-2003, School of Ocean and Earth Science, Southampton University. Abstract: There is a succession of Late Jurassic/Early Cretaceous lagoonal strata present on the west coast of the Isle of Portland. There is a transition upwards from low to high salinity. There are palaeosols indicating shallower conditions in places, allowing ancient soils to form. There are two evaporite beds present, which contain lutecite, which is an indicator of evaporites. High energy is indicated by ripple laminations in some limestone beds and coarser particle size in the Hard Slatt. The gypsum discovered is secondary gypsum in the upper evaporite beds and good pseudomorphs after halite are present in the upper limestone beds. The section is an example of hypersaline lagoon conditions which in this region marked the regression at the end of the Jurassic Period. [Report by Jennifer Will on her student project. One copy filed at Southampton University.]
General Introduction
Portland-Background
Geography in the national and school curriculum
town and country planning system statistical information
Case Studies
Involving Decision Making Exercises and role play.
(1) Portland Naval Base and Portland Harbour Management Plan
(2) Chesil Beach and the Fleet - The Ferrybridge Management Plan
(3) Markham and Little Francis - New Housing and Environmental Constraints.
(4) Portland Stone and Quarries - Geology, history, quarrying, waste disposal and re-use of land.
(5) Portland Bill - Leisure and Recreational Potential
(6) Retail Surveys of Shopping Centres on Portland
(7) Tourism Development Strategy for Portland
(8) Weymouth Town Trails.
(9) Sea Defence Schemes at Chesil Beach, Portland and Preston, Weymouth.
(10) Proposed Relief Roads to serve Weymouth and Portland.
This guide to Geographical Enquiries using Fieldwork on the Island and Royal Manor of Portland has been prepared by Weymouth and Portland Borough Council's Planning Department on behalf of the South Dorset Economic Partnership. The initiative is being promoted as part of the Single Regeneration Budget Programme for Portland and is aimed at attracting geography field study visits to the Portland, Weymouth and South Dorset area, with a view to visiting groups of students staying on the Island or in the locality, to the benefit of the local economy.
The area is subject to major economic restructuring as a result of the closure of defence establishments on Portland and this initiative itself is part of the strategy being implemented to diversify the local economy. The natural and environmental assets and other physical and geographical attributes of the area make it an ideal location for field study visits. Current planning and environmental issues in the area have been presented in this guide in a Case Study format suitable for use at different ability and curriculum levels, from Key Stage 3 to A Level. A wide range of information is also provided to help make the planning and implementation of field study visits to Portland easier for teachers and lecturers.
The ten Case Studies in this guide deal with a wide range of subject matter and involve survey/fieldwork, decision making and role play exercises. They are based principally on the Island of Portland but where appropriate, focus on examples in Weymouth, notably relating to housing pressures, town trails and a comparative Sea Defence Case Study.
North quay
Weymouth
Dorset DT4 8TA
Tel 01305 206333, fax 01305 766773
.
Wilson
, R.C.L. 1966. Silica diagenesis in Upper Jurassic limestones of southern England. Journal of Sedimentary Petrology, 36, 1036-1049. Abstract: Silica diagenetic fabrics occurring in the Portland and Corallian Beds of southern England are described. On the basis of their morphology, five major fabric types are distinguished: mosaic quartz, chalcedonic overlays, spherulitic chalcedony, lutecite, and microcrystalline granular quartz. Of these, the first three may be cementation fabrics, and all except chalcedonic overlays may exhibit replacement features. The silica fabrics are dated according to their relation to carbonate diagenetic fabrics. Two major stages of silicification are demonstrated, the first being pre-calcite cement fabrics and the second post-calcite cement fabrics; each was probably accompanied by calcitization of sponge spicules. The latter occur in sufficient quantities throughout the sediments to account for the silica fabrics. Lack of silicification in the Corallian Beds, despite their high spicule content, is probably caused by calcite cements effectively reducing porosity early in their diagenetic history. This contrasts with the extensive development of cherts in the Portland Beds, in which high porosities are maintained after deposition to the present day.
.
Wimbledon
, W.A. 1987. Rhythmic sedimentation in the Late Jurassic-Early Cretaceous. Proceedings of the Dorset Natural History and Archaeological Society, 108 for 1986, 127-133. Most of this paper is on the Portland Group. An Appendix refers to Purbeck nomenclature. Abstract: A number of shallowing and deepening phases is described in the late Kimmeridgian - Berriasian interval. Eleven deepening / transgressive events are noted in the most complete Dorset section. A preferred lithostratigraphy for these beds is compared to previous lithostratigraphy, and "event correlations" are critically examined.
.
Woodward
, H.B.1895. The Jurassic Rocks of Britain. Vol 5. The Middle and Upper Oolitic Rocks of England (Yorkshire excepted). Memoirs of the Geological Survey of the United Kingdom. 499pp.
2. PORTLAND BIBLIOGRAPHY CONTINUED - DIVIDED INTO TOPICS
For Chesil Beach Bibliography see Chesil Beach Field Guide
References cited in the Portland Field Guide, but not listed in other sections
2.1 TOPICS - Chesil Beach
2.2 TOPICS - Other References
...
Barker
, D., Brown, C.E., Bugg, S.C. and Costin, J. 1975. Ostracods, land plants and charales of the basal Purbeck Beds of Portesham Quarry. Palaeontology, 18, 419-436. Fauna and flora of the Portesham charophyte chert.
...
Bell
, M. and Walker, M.J.C. 1992. Late Quaternary Environmental Change: Physical and Human Perspectives. Longman Scientific and Technical, Harlow, Essex, England. 273 pp. ISBN 0-582-04514-2.
.
West
, I.M. 1961. Lower Purbeck Beds of Swindon facies in Dorset. Nature, London, 190, 526. Extract: ' .. a marl has been discovered with a fauna resembling that of the freshwater facies of the 'Swindon Series'. In the well-known Portisham [or Portesham] quarry with the 'fossil elephant' [stromatolitic limestone around a tree trunk], the tree-foot "impure marls with seams of chert" listed by Woodward as occurring 9 feet, 6 inches above the Portland Stone have been found to contain the Swindon ostracod Ulwellia papulata Anderson, and well-preserved charophytes in abundance. Gastropods are also abundant and perhaps have Swindon affinities... continues. [The fauna and flora discovered in the Portesham Charophyte Chert was subsequently described by Barker, D., Brown, C.E., Bugg, S.C. and Costin, J. 1975. Ostracods, land plants and charales of the basal Purbeck Beds of Portesham Quarry. Palaeontology, 18, 419-436.]
.
Allen
, T.D. 1863. Mammalian and human remains. Isle of Portland. Geologist, 6, 94, 136, 251.
Allen, T.D. 1863. The Portland fissures with human remains. Geologist, 6, 209, 293.
...
Anonymous
, 1869. . Hitcraft Quarry in Wide Street, Portland, near St George's Church , Reforne. A cavern was found 56 feet below surface, 600 yards long, full of stalactites 2-3 feet long, cream, amber etc. also "curious petrifactions" Dorset County Chronicle
,16, (9), 3, (23.09.69).
.
Anonymous
, 1972. Finding the hidden world under Portland. Mid Week Magazine
, Wednesday, August 30, 1972.
...
Churcher
, R.A., Butler, B. and Bartlett, P.D. 1970. A further report on the caves of the Isle of Portland. Transactions of the Cave Research Group of Great Britain, vol. 12, No. 4, 291-298.
...
Falconer
, H. 185? On Portland ossiferous fissures. (not seen - details not known - probably about 1850-1865)
.
Fisher
, O. 1861. Fissures in Portland strata. Geologist, 4, 556.
Fisher, O. 1863. The Portland ossiferous fissures. Geologist, 6, 250.
.
Ford, T.D. and Hooper, M.J. 1964. The caves of the Isle of Portland. Cave Research Group of Great Britain, Transactions, 7, 13-37. (Sawmill Cave in Inmosthay Quarries, Thrutch Cavern - still accessible, amongst the rubbish, in Higher Headland Quarry, Cherty Rift and Australia Rift on the east coast, St George's Fissure in Bower's Quarry. Steve's Endeavour Fissure in the cliff west of Bower's Quarry.)
Ford, T.D. and McTurk, G. 1969. The stereoscan microscope and speleothems. Transactions of the Cave Research Group of Great Britain, 11, No. 4, Dec. 1969. 241-243 plus plates. (speleothems from Thrutch Cavern).
.
Graham
, N. 1994. Caves of Portland. The Geology and Caves of Portland. 15 pages plus notes on Blacknor Hole, Sandy Hole and references.
Graham, N. 1995. Letter to IMW re Dorset caves. Dancing Ledge solution tube. Karst cave at Emmett's Hill. Doline at West Stafford. Book by Graham on Portland caves.
Graham - book - details to be added.
...
Hollingworth
, S.E., Taylor, J.H. and Kellaway, G.A. 1943. Large scale superficial structures in the Northampton Ironstone field. Quarterley Journal of the Geological Society of London, 100, 1-44. Gulls, Gulleys on Portland, Camber, Valley Bulge.
.
Neale
, A. 1852. Notice of fossil bones at Portland. (From a letter to the secretary of the Geological Society). Quarterly Journal of the Geological Society, 8, p. 109 only (1 paragraph). [Molar tooth of horse in fissure in northeastern Portland.]
.
Prestwich
, J. 1875. Notes on the phenomena of the Quaternary period in the Isle of Portland and around Weymouth. Quarterly Journal of the Geological Society, London, 31, 29-54. [Raised beach, landslides, beef and middle Purbeck detritus at Portland Bill, Chesil Beach, vertebrate remains in fissures, the Portland Mammaliferous Drift etc.]
Prestwich, J. 1892. The raised beaches and 'Head' or rubble-drift, of the south of England; their relation to the valley drifts and to the Glacial Period; and on a late post-Glacial submergence. Quarterly Journal of the Geological Society, London, 48, 263-343.
.
Stopes
, M. and .... 1953(?). (on human bones found in a fissure in a small quarry at Bumpers Lane, near Easton, Portland. Also stone artifacts) Proceedings of Dorset Natural History and Archaeological Society [details to be added].
[END OF 2.3 TOPICS - Portland Caves and Fissures]
2.4 TOPICS - Portland East and West Cliffs
(and related landslip literature)
.
Admiralty
Charts, 1844. Weymouth and Portland Roads, with sections of the Chesil Beach. Surveyed by Comm. W. Sheringham. Ref. L4021.
Admiralty Charts, 1855. Bill of Portland to Abbotsbury. Surveyed by Lt.H.L. Cox, J.C.B. Usborne and J.E. Davis. Ref. D1821 & D8052. .
...
Allen
, J.R.L. 1985. Principles of Physical Sedimentology. London, George Allen and Unwin, 272p. [See page 165 et seq. Rotational slides - bowl-shaped glide surfaces - amphitheatres. Crown cracks. Aprons of disturbed ground with pressure ridges (and thrusts?). Failure occurs under conditions of significantly raised pore-water pressure. Translational slides - gathering region, chutes, accretionary lobe with disturbed ground and thrusts(?). Bordering faults occur. Debris aprons. Not on the subject of Portland but relevant to landslides.]
Allen, T.D. 1863. Mammalian and human remains. Isle of Portland. Geologist, 6, 94, 136, 251.
Allen, T.D. 1863. The Portland fissures with human remains. Geologist, 6, 209, 293.
.
Andrews, J.T., Bowen, D.Q. and Kidson, C. 1979. Amino acid ratios and the correlation of raised beach deposits in south west England and Wales. Nature, London, 281, 556-558.
...
Anonymous
. 1859. Landslip at the Isle of Portland. Geologist, 2, 127-128. Early on Sunday morning, 26th December 1858 - noise like the continual falling of a stone wall. 20 - 25 acres of undercliff slid away. Sinking of enormous mass of broken stone, the debris of adjoining quarries and the accumulation of very many years. West side of the island overlooking the great West Bay. 200 or 300 yards from the village of Chesil. A slight sinking the previous afternoon. Collapse an hour after midnight. The main cliff is at this point about 200 feet above the level of the sea, the north end is 495 feet with a southerly dip. Kimmeridge Clay pushed forward beyond the beach into the water and forced upward with the shingle over it so as to present an escarpment towards the sea. A small pond behind. Plots rotated from a seaward dip through 90 degrees so as to dip landwards. A crack of a few inches in the solid cliff above. (Was this in the cliff below the Tout Quarries or below the Trade Quarries?)
Anonymous. 1859.01.20. Landslip at Portland. Dorset County Chronicle, 5, 485.
Anonymous. 1823. " Earthquake shock " Island of Portland. (in reality a cliff fall R. Musson pers. comm. to Thomas) 16.12.c1735. Notes and Queries for Somerset and Dorset, 17, (113), 139.
Anonymous. 1859.01.13. The landslip in the Island of Portland. (Sunday, 06.12.1858. Outline of the Geology of the Strata) Dorset County Chronicle, 5, 466.
Anonymous. 1981.11.27. (Chesil Beach coast protection, photo and text). Dorset Evening Echo.
Anonymous. 1982.04.22. Sea defence consultants change mind on Portland Stone. Dorset Evening Echo. .
Anonymous. 1983.02.18. Test hole plan at Chesil Beach. (boreholes?) Western Gazette. .
Anonymous. 1983.04.29. Portland sea defences progress. Western Gazette. .
Anonymous. 1983.08.08. Chesil Beach Probe under way. Dorset Evening Echo. .
Anonymous. 1986.09.26. Mystery tremors at Portland. Dorset Evening Echo. .
...
Barton
, M.E. and Coles, B.J. 1984. The characteristics and rates of the various slope degradation processes in the Barton Clay Cliffs of Hampshire. Quarterly Journal of Engineering Geology, London, 17, 117-136. [A useful paper for comparison but not directly on the subject of Portland.]
Barton, M.E., Coles, B.J. and Tiller, G.R. 1983. A statistical study of the cliff top slumps in part of the Christchurch Bay coastal cliffs. Earth Surface Processes and Landforms, 8, 409-422. Some use for comparison but not directly on Portland.
...
Bromhead
, E.N. 1992. The Stability of Slopes. Blackie. Not on Portland but relevant to landslides.
...
Brunsden - Professor Denys Brunsden
Brunsden, D., Coombe, K., Goudie, A.S. and Parker, A.G. 1996. The structural geomorphology of the Isle of Portland, southern England. Proceedings of the Geologists' Association, London, 107, 209-230. [This is a key paper.] Authors' Abstract: The Isle of Portland, southern England, is composed of gently folded Upper Jurassic Beds ranging from the Kimmeridge Clay through the Portland Group to the Lower Purbeck Group which are gently folded to form part of the northern end of the Shambles Syncline. The essential arrangement of the beds is for hard, jointed well-bedded and permeable Purbeck and Portland limestones to overlie the Kimmeridge Clay members. The jointing along NW-SE, NE-SW, N-S and E-W master and conjugate sets closely parallels the axis of the syncline and the NNE-SSW fault pattern of the Purbeck Anticline and is a major regional landform control at all scales from the occurrence and form of individual rock falls to the shape of the island itself. Portland has a large number of landslips, which have been mapped from colour air photography. Their spatial pattern is spectacularly related to the geological conditions of the island and varies in size and type in a systematic manner as the thickness of clay and orientation of the dip changes with respect to coastline orientation. The slips, which occur predominantly in the winter months after heavy rainfall, are of frequent occurrence and pose major hazards to engineering structures. The landslide pattern and the overall morphology of the island is used to suggesta tentative model of landscape evolution which emphasizes the process of lateral spreading, loading, clay extrusion and erosional unloading. End of authors' abstract. [Some further notes from the paper: Maps and dates of Portland landslips since 1615, including a major one on the East Weare in 1792. Seasonal distribution of slips - February, March. Joints. Coombe's joints. Development of a synclinal structure by extrusion of a ductile underlayer. Relation to Shambles syncline. No faulting.]
Brunsden, D. and Goudie, A. 1981. Classic coastal landforms of Dorset. Geographical Association, Landform Guides, No. 1, 39 pp.
Brunsden, D. and Jones, D.K.C. 1976. The evolution of landslide slopes in Dorset. Philosophical Transactions of the Royal Society, London, A 283, 605-631.
[You are in: "2.4 TOPICS - Portland East and West Cliffs"]
...
Carr
, A.P. 1969. Size grading along a pebble beach; Chesil Beach, England. Journal of Sedimentary Petrology, 39, 297-311.
Carr, A.P. and Blackley, M.W.L. 1969. Geological composition of the pebbles of Chesil Beach, Dorset. Proceedings of the Dorset Natural History and Archaeological Society, 90 (for 1968), 133-140.
Carr, A.P. and Blackley, M.W.L. 1973. Investigations bearing on the age and development of Chesil Beach, Dorset and the associated area. Transactions of the Institute of British Geographers, 58, 99-111.
Carr, A.P. and Blackley, M.W.L. 1974. Ideas on the origin and development of Chesil Beach, Dorset. Proceedings of the Dorset Natural History and Archaeological . Society (for 1973), 95, 9-17.
.
Coombe
, E.D.K. 1982. Some Aspects of Coastal Landslips and Cliff-falls at Portland. Dissertation in the Bodleian Library, Oxford and the School of Geography, Oxford. This also exists, probably unchanged, in the form of an unpublished typescript for the Proceedings of Dorset Natural History and Archaeological Society, with 29 text-pages and 31 figures. The Dorset Proceedings version was not published because of its large size and dissertation format. By Mr. Ken Coombes of Exbourne, Wakeham, Portland, who at the time was a teacher of geography at Thornlow School, Weymouth. He received the Royal Geographical Society's annual award and Fellowship for this dissertation. [This is an extremely interesting account full of useful information on Portland and particularly on landslides. In particular it includes a map of joints on Portland. There is information on quarrying and history etc.]
Extract: As many geographers have pointed out, probably more has been written about the Dorset coast than about
any other comparable stretch of British coastline and it includes the Island of Portland as part of its appeal,
especially to the geomorphologist. Comparing the Dorset
coast with/the Hampshire Basin to the East, and that of
Devon to the west, one is faced with a coastline that is
intermediate in character as well as in position. From the Permian at Paignton eastwards to Portland Bill, the whole of Lyme Bay has been eroded in generally soft Triassic and Jurassic deposits. It would seem that virtually all traces of an older coastline have been removed since the last significant sea level rise, leaving only the platform and raised beach at Portland Bill extant.
It is probably true that the Island of Portland's preservation is largely unexplained, more so, perhaps, as there is now firm evidence of a sea-floor continuation of Portland strata planed off during some previous marine epoch affectin:.:~ an area eastwards to Purbeck, and westwards into Lyme Bay (Donovan and Stride, 1961). Thus ,one may infer that the island of Portland probably stood up as an island hill on some interglacial marine platform, and may be analagous to the chalk Highdown Hill standing above the Sussex coastal plain today.
Arkell (1947) p. 342, maintains that... "Portland came into existence as a headland 4 miles long since the middle of the Palaeolithic period or thereabouts..."
As Steers (1954) p.260 suggests that post-glacial sea level changes were rapid enough for peat to be preserved on the Dogger Bank, it seems possible, ceteris paribus, that the relatively hard Portland Stone would preserve traces of an older cliff line, possibly of more than one age and of one level, along the Dorset Coast.
Because Portland is thus the. last vestige of the southern limb of the Weymouth anticline, it is unique not only as a relict landform, but also as an area for geomorphological study, especially of the effects of the Quaternary period. Portland has a relatively long coastline of some 15 kilometres under continuous wave attack encompassing an ever decreasing planimetric area currently of approximately 1160 hectares. Strahan (1898) p.114 quotes Dr. Fitton as maintaining...
"Few places, probably in the world, exhibit with such clearness, and in so small a space, phenomena of more extraordinary interest and of greater importance to theory..."
It has long been noticed that the cliff falls and landsli at Portland are a prominent and noteworthy feature of the is land topography. Observers as early as Leland (1546) and Hutchins (1710), and as recent as Perkins (1977), have historically and variously regarded them as resulting from earthquake, Acts of God, etc., and more recently as rotational slips, or topples due to structural weaknesses in the lithology combined with wave attack.
The presence of the adjacent Chesil Beach is evidence of the massive 7,000 mile fetch from the southwest, and implies high wave energy expended on the island (Plate No. 1). The raised beach at Portland Bill with its axis at 90 degrees to Chesil also implies a dominant fetch at a former higher sea level and from a different direction.
However important one regards marine erosion as a factor in the cliff falls, it is untrue to suggest that the sea has necessarily been a factor in all the slips on the island; but this adds greatly to the problems.
Arkell (1947) (op.cit., p.353) notes:
"The landslips round the cliffs of the northern
half of Portland are to some extent intermediate between normal cliff slides and inland slips, for some are ancient and date from the original formation of the escarpment, before the sea approached. Others are
very recent and are documented..."
It seems that little, if any, work has been published
to date giving clear definitive description of the falls and slips, and apparently none with evidence to explain the complex nature of the falls, which from the writer's investigation cannot be placed into anyone simple category, but raise more problems than they answer.
The vertical jointing running throughout the island has attracted much attention from geologists and others
during the past 120 years. For example, Gray (1861) p.129, noted:
"Fissures which traverse the island from NE to SW, and extend from within a few feet of the surface down to the clay. It would seem also, from the fact of the fissures being independent of any particular bed, that they were produced subsequent to the deposition of the most recent formation developed on the island. The direction of the fissures is so constant, that quarrymen profess to ascertain, very nearly the hour of the day by the extent of the shadow cast in the opening.." ... [continues].
...
Carreck
, J.N. and Ford, T.D., 1966. The fauna of the Portland caves and fissures, Dorset, The Transactions of the Cave Research Group of Great Britain, vol.7, No. 2, 205-208.
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Damon
, R. 1884. Geology of Weymouth, Portland, and Coast of Dorsetshire, from Swanage to Bridport-on-the-Sea: with Natural History and Archaeological Notes. New and Enlarged Edition (2nd Ed.), Weymouth, R.F.Damon, London, Edward Stanford. 250p. See page 157 et seq. from which comes the following extracts. "... This was illustrated in the landslip of Dec. 26th, 1858, when the sliding down of an extent of undercliff covering an area of twenty-five acres caused the sinking of an enormous mass of broken stone, the debris of adjoining quarries and the accumulation of very many years. ... west side of the Island overlooking West Bay. ... low undercliff of Kimmeridge Clay, which, from lateral pressure, was pushed forward beyond the beach into the sea and forced upwards with the shingle over it, so as to present a steep outer face towards the sea. A little way up the cliff .... some garden plots, which previously inclined towards the sea at an angle of 45 degrees, but dip now as much in the opposite direction, the plane of this portion of land having consequently traversed 90 degrees... The entire ground from the beach upwards was rent with innumerable cracks running in lines parallel to the coast and rising in a series of steps or terraces. For many years the debris of the adjoining quarries had been thrown from trucks over the cliff, forming a kind of causeway extending some forty feet, all of which sunk bodily down into basin-shaped cavities beneath, and carried with it portions of the main cliff. Either from the sudden withdrawal of this enormous mass, or the undermining which had gone on below, there was a partial severance of a large part of the solid cliff, which left an open crack several inches in width. ..." Also notes on the Chesil Beach.
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Denness
, B. 1972. The reservoir principle of mass movement. Report of the Institute of Geological Science, London., 72/3. [Theory relevant to Portland.]
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Edmunds
, F.H. and Schaffer, R.J. 1932. Portland Stone; its geology and properties as a building stone. Proceedings of the Geologists' Association, London, 43, 225-240.
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Gibbs
, P. 1982. Observations of short term profile changes on Chesil Beach. Proceedings of the Dorset Nat History and Archaeological Society, 102 (for 1980), 77-82.
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Goudie
, A. and Brunsden, D. 1997. Classic Landforms of the East Dorset Coast. Published by the Geographical Association in conjunction with the British Geomorphological Research Group. Sheffield. 48 pp. Series Editors - Rodney Castleden and Christopher Green. Low cost paperback , pocket size booklet. Concise with excellent colour illustrations including good aerial photographs. Sections comprise: Introduction, the Portland Cliff, the Portland Raised Beach, the south Dorset coast, the Lulworth Coast, the east Purbeck coast, Studland Bay and the South Haven Peninsula, Poole Harbour, Glossary, Bibliography. (see also companion volume on West Dorset).
Graham, J.T. 1954. A visit to Portland. The Dorset Year Book 1953-4.
[This is part of: 2.4 TOPICS - Portland East and West Cliffs]
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Hollingworth
, S.E., Taylor, J.H. and Kellaway, G.A. 1943. Large scale superficial structures in the Northampton Ironstone field. Quarterley Journal of the Geological Society of London., 100, 1-44. Gulls, Gulleys on Portland, Camber, Valley Bulge.
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Hounsell
, S.S.B. 1952. Portland and its stone. Mine and Quarry Engineering, 18, 107-114.
Hounsell, S.S.B. 1962. The quarrying of Portland Stone. The Quarry Manager's Journal, 1962, 1-8 (of reprint).
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House
, M.R. 1970. Portland Stone on Portland. Proceedings of the Dorset Natural History and Archaeological Society, 91, (for 1969), 38,39.
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Hutchins
, J. 1861. The History and Antiquities of the County of Dorset. Ed. 3, By Shipp, W. and Hodson, J.W. London. Pp. 807 - 832. [The Island and Liberty of Portland. Camden says it was formerly an island although now annexed to the continent. Holinshed and Leland of same opinion. Beale Point. The Beell. 1710 map showing the West Cliffs. Broadly similar as at present. The Clay Ope Amphitheatre is visible. The north end of the landslip area looks similar to the present but there is no tip shown and no obvious Tar Rocks promontory. The map is not accurate. The Mare is shown. . Attributed to much use of spirits. Ancient British Baleares - used to fling stones. Kimmeridge Coal is present and burnt and used for manure. Grotos and caverns at Portland Bill. Keeve's Hole - one of the wonders of Portland. Vegetable mould - Purbeck palaeosol. Chesil pebbles - Portland pebbles. Travertine in the southwest quarries. Kimmeridge coal worked half a mile east of the Castle in the north of the island. Fossils. Cave Hole. Weirs - uneven slopes of grassland formed by successive landslips. Chesil or Steepstone (step-stone) beach. German Keisel - flint or Ceorl - Saxon - Gravel.]
[This is part of: 2.4 TOPICS - Portland East and West Cliffs]
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Jeffreys
, J.G. 1875. Notes on the fossil shells . In: Prestwich, J. Notes on the phenomena of the Quaternary period in the Isle of Portland and around Weymouth. Quarterly Journal of the Geological Society, London, 31.
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Jones
, M.E., Allison, R.J. and Gilligan, J. 1984. On the relationship between geology and coastal landform in central southern England. Proceedings of the Dorset Natural History and Archaeological Society, 105 (for 1983), 107-118.
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Kerney
, M.P. and Cameron, R.A.D. 1979. A Field Guide to the Land Snails of Britain and North-West Europe. Collins, London.
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Melville
, R.V. and Freshney, E.C. 1982. The Hampshire Basin and adjoining areas. Institute of Geological Science, H.M.S.O., 146pp.
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Neale
, A. 1852. Note on fossil bones at Portland. Quarterly Journal of the Geological Society, London, 8.
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Pentin
, H. 1916. Old Portland. Proceedings of the Dorset Natural History and Archaeological Society, 37, 228-253.
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Pitts, J. 1982. An historical survey of the landslips of the Axmouth-Lyme Regis undercliff, S. Devon. Proceedings of the Dorset Natural History and Archaeological Society, 103 (for 1981), 101-106.
Pitts, J. 1984. The recent evolution of landslipping in the Axmouth-Lyme Regis Undercliffs National Nature Reserve. Proceedings of the Dorset Natural History and Archaeological Society, 105 (for 1983), 119-125. Relevant for comparison.
[You are in: 2.4 TOPICS - Portland East and West Cliffs]
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Prestwich
, J. 1875. Notes on the phenomena of the Quaternary period in the Isle of Portland and around Weymouth. Quarterly Journal of the Geological Society, London, 31, 29-54. [Raised beach, landslides, beef and middle Purbeck detritus at Portland Bill, Chesil Beach, vertebrate remains in fissures etc.]
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Rothwell
, C. 1986. Weymouth in Times Past. Chamberlain Publishing Ltd. 48p. Old pictures of Portland.
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Walshaw
, G. 1993. An Environmental Study of the Eastern Cliffs of the Isle of Portland, Dorset. B.Sc. Hons. Environmental Science Project, University of Southampton, 1993. By Genevieve Walshaw. 32 pp + appendices, maps and diagrams. Abstract: The following report presents the findings of a third year undergraduate research project on the eastern cliffs of the Island of Portland, Dorset, completed in 1992-1993. The study involved detailed mapping of the landslide units and their mechanisms, the geomorphology of the area and the biological communities present. Geological and biological cross sections of the site have been drawn and analysed for relationships. The degradation processes on the eastern coast of the Isle of Portland consist of a combination of topples and rotational slides. Rotational slides are dominant in the north and topples are dominant in the south. Trends in plant communities exist as a result of the geomorphology that the cliff falls create.
[This was a First-Class Honours standard undergraduate project and it contains much useful information.]
[You are in: 2.4 TOPICS - Portland East and West Cliffs]
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Williams
, N. 1992. A Study of the Landslides at the West Weare Cliff, Portland, Dorset. Unpublished Undergraduate Environmental Science Project for B.Sc. University of Southampton, 64pp + Tables, Figures and Appendices. Abstract: This report presents the results of a final year undergraduate research project on the landslides on the West Weare Cliffs of Portland, Dorset, undertaken in 1991/92.A detailed field study of the landslides, their mechanisms and other degradation processes is presented together with their relationship to the geological, geomorphological and biological composition of the area. The study is augmented by published data and information gained from current leading authorities on the area. An estimate of recent coastline retreat is given and discussed together with predictions of the areas of potential future movement. Evidence is presented to date the landslides using historical records, old photographs and maps of the area. [This is an unusually good student project, with much interesting information.]
2.5 TOPICS - Portland Landslide Analogues
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Parks, C.D. 1991. A review of the mechanisms of cambering and valley bulge. Pp. 373-380 in: Forster, A., Culshaw, M.G., Cripps, J.C., Little, J.A. and Moon, C.F. (eds). 1991. Quaternary Engineering Geology, Geological Society Engineering Geology, Special Publication, No. 7, 724p. [Development of gulls, bulging and stress relief gives dips away from the cliffs much like Portland.]
2.6. TOPICS - Portland Raised Beaches
(more to be added)
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Arkell
, W.J. 1949. Erratics in Dorset shingle beaches. Proceedings of the Dorset Natural History and Archaeological Society, 70, 125.
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Brokenshire, A. 1997. Visit to Dorset by Reading Geological Society, 12-14th September, 1997, Leader Adrian Brokenshire. Dorset Group of the Geologists' Association Newsletter, October, 1997. pp 6-7.
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House, M.R. 1993 (and earlier edition in 1989) - Geology of the Dorset Coast. Geologists Association Guide No. 22. 2nd edition, 164 pages plus plates. ISBN 0 7073 0485 7. (This inexpensive, conveniently small, paper back guide should be carried in the field as a very useful source of information by all seriously studying the geology of the Dorset coast. It is full of detailed information and is concise and accurate. It enables field leaders to obtain essential information quickly and without carrying much weight of publications. )
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Davies
, K.H. and Keen, D.H. 1985. The age of Pleistocene marine deposits at Portland, Dorset. Proceedings of the Geologists' Association, 96, (3) 217-225. (Key Paper. Authors' abstract: The deposits have been known for 145 years as providing evidence of high Pleistocene sea-levels. Most accounts have relied on nineteenth century descriptions of the deposits and their fauna. Such accounts emphasise the supposed similar ages of the marine deposits on both west and east sides of the peninsula, despite their differences in facies and faunal content. This paper reports the results of new work based upon mapping and levelling the deposits and the amino acid analysis of the fauna. The results suggest the existence of two stratigraphically and geochronologically separate marine deposits at Portland. It is proposed that there is a correlation with oygen isotope stage 5e (c. 125,000 BP) for the beach on the east side of Portland Bill and a correlation with oygen isotope stage 7 (c. 210,000 BP) for the beach on the west side of Portland Bill.)
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De La Beche
, H.T. 1839. The Geology of Cornwall and Devon and a Part of West Somerset. Memoir of the Geological Survey of Great Britain.
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Keen
, D.H. 1985. Late Pleistocene deposits and mollusca from Portland, Dorset. Geological Magazine, 122 (2), 181-186. (Author's abstract: The stratigraphy and fauna of terrestrial deposits at Portland Bill is described. The fauna is restricted to the head and is indicative of a cool climate rather than the temperate conditions suggested by earlier authors. An age in the Devensian Glacial Stage is tentatively suggested.)
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Kellaway, G.A., Redding, J.H., Shephard-Thorn, E.R. and Destombes, J-P. 1975. The Quaternary history of the English Channel. Philosophical Transactions of the Royal Society, London, Series A, 279, 189-218. In: Dunham, K., and Smith, A.J. 1975. A Discussion on the Geology of the English Channel. The Royal Society, 6 Carlton House Terrace, London, SW1Y 5AG. Abstract: "Several lines of evidence for former glaciation of the English Channel are considered. These include the following major geomorphological features: (1) extensive areas of flat featureless sea bed bounded by cliffs with residual steep-sided rock masses rising about 60-150m above them., (2) terrace forms bounded by breaks in slope or low cliffs, (3) palaeovalley systems attributed to present land drainage, (4) enclosed deeps (fosses); all except (3) may be attributed to a glacial origin. The distribution of erratics on the Channel floor and in modern and raised beaches of its coasts are attributed to widespread Saalian glaciation. This glaciation was responsible for the deposition of morainic material at Selsey and the damming-up of glacial Lake Solent. The so-called '100 foot raised beach' of west Sussex is now re-interpreted as a fluvioglacial deposit laid down at the northern margin of the English Channel ice. It is thought that at the height of the Saalian glaciation mean sea-level fell to between 90 and 100 m below O.D. and that for a time the ice was grounded near the western margin of the continental shelf. Possible reconstructions of the limits and main movements of the Weichselian and Saalian ice sheets covering the British Isles and English Channel are included. " See pp 206-7 for mention of Portland raised beach. The whole (controversial) theory of an English Channel glacier is relevant to the Portland raised beach or beaches.
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Prestwich
, J. 1875. Notes on the phenomenon of the Quaternary period in the Isle of Portland and around Weymouth. Quarterly Journal of the Geological Society, London, 31, 29-54.
Prestwich, J. 1892. The raised beaches and 'Head' or rubble-drift, of the south of England; their relation to the valley drifts and to the Glacial Period; and on a late post-Glacial submergence. Quarterly Journal of the Geological Society, London, 48, 263-343.
2.7 TOPICS - Portland Stone Formation
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Arkell
, W.J. 1933. The Jurassic System in Great Britain. Clarendon Press, Oxford, 344p.
Arkell, W.J. 1947. The Geology of the Country around Weymouth, Swanage, Corfe and Lulworth. Memoir of the Geological Survey, 386 pp. Explanation of Sheets 341, 342, 343, with small portions of Sheets 327, 328 and 329. By W.J. Arkell, M.A., D.Sc., with contributions by C.W. Wright, M.A. and H.J. Osborne White, F.G.S. London, Published by Her Majesty's Stationery Office, 1947, reprinted 1953. [This classic publication covers almost the same area as that of Strahan's 1898 memoir and is an update to 1939 with some small additions to 1944.]
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Blake
, J.F. 1880. On the Portland rocks of England. Quarterly Journal of the Geological Society, London, 36, 189-236. With notes and descriptions of Portland fossils and comparitive sections of the Portland rocks of England. By the Rev. J.F. Blake, M.A., F.G.S. Pp 190 -193 on the Isle of Portland [not highly detailed regarding the Isle of Portland but with information of Swindon, Vale of Wardour and elsewhere].
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Bosence
, D.W.J. 1987. Mesozoic platform carbonates and benthic calcareous algae of the Severn and Wessex Basins. In: 4th International Symposium on Fossil Algae, Cardiff, July, 1987, edited by Robert Riding. Pre-Symposium Field Excursion, Excursions Guide, pages unnumbered. [See section: Portland and Purbeck Formations of the Isle of Portland. End-Jurassic regressive sequence with oncoids, oyster/Solenopora reefs, trees, palaeosols and tufas.]
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Callomon
, J.H. and Cope, J.C.W. 1995. The Jurassic Geology of Dorset. In: Taylor, P.D. (ed.). Field Geology of the British Jurassic. Geological Society, London, pp. 51-103. (See p. 56 on the Blue Lias. See p. 59 and 60 on the Bridport Sands)
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Cox
, L.R. 1925. The fauna of the basal shell bed of the Portland Stone, Isle of Portland. Proceedings of the Dorset Natural History and Antiquarian Field Club, 41, 113-172.
Cox, L.R. 1929-1930. A synopsis of the lamellibranchia and gastropoda of the Portland Beds of England. Proceedings of the Dorset Natural History and Antiquarian Field Club, 50, 131-202.
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Damon
, R. 1884. Geology of Weymouth, Portland, and Coast of Dorsetshire, from Swanage to Bridport-on-the-Sea: with Natural History and Archaeological Notes. New and Enlarged Edition (2nd Ed.), Weymouth, R.F.Damon, London, Edward Stanford. 250p
Falcon-Lang, H.J. 1998. A Geological Survey of the Isle of Portland, Dorset. Undertaken by Dr H.J. Falcon-Lang, Department of Geology, Royal Holloway College, University of London, Egham, Surrey, TW20 0EX, UK for "The Jurassic Coast Project", Dorset County Council, UK, October, 1998. 86 pages with maps, diagrams and photographs.
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Fitton
, W.H. 1835. Notice on the junction of the Portland and Purbeck strata on the coast of Dorsetshire. Proceedings of the Geological Society, London, 2, 185-187.
Fitton, W.H. 1836. Observations on some of the strata between the Chalk and the Oxford Oolites, in the south-east of England. Transactions of the Geological Society, London, 4, 103-389.
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Quest
, M. 1985. Petrographic and Geochemical studies of the Portland and Purbeck Beds of Dorset. Unpublished Ph.D. Thesis, Geology Dept., University of Birmingham, England, 347pp.
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Townson, W.G. 1971. Facies Analysis of the Portland Beds. Unpublished. D.Phil. thesis, Oxford University., 284pp.
Townson, W.G. 1975 Lithostratigraphy and deposition of the type Portlandian. Journal of the Geological Society of London, 131, 619-638. (Key Paper)
Townson, W.G. 1976. Discussion of Portlandian faunas. Journal of the Geological Society of London, 132, 335-336.
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Wilson
, R.C.L. 1967. Diagenetic carbonate fabric variations in Jurassic limestones of southern England. Proceedings of the Geologists' Association, London, 78, 535-554.
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Wimbledon, W.A. 1987. Rhythmic sedimentation in the Late Jurassic-Early Cretaceous. Proceedings of the Dorset Natural History and Archaeological Society, 108 for 1986, 127-133. [Most of this paper is on the Portland Group. An Appendix refers to Purbeck nomenclature. Abstract: A number of shallowing and deepening phases is described in the late Kimmeridgian - Berriasian interval. Eleven deepening / transgressive events are noted in the most complete Dorset section. A preferred lithostratigraphy for these beds is compared to previous lithostratigraphy, and "event correlations" are critically examined. ]
Wimbledon, W.A. and Cope, J.C.W. 1978. The ammonite faunas of the English Portland Beds and the zones of the Portlandian Stage. Journal of the Geological Society, London, 135, 183-190. (Key Paper).
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Woodward
, H.B.1895. The Jurassic Rocks of Britain. Vol 5. The Middle and Upper Oolitic Rocks of England (Yorkshire excepted). Memoirs of the Geological Survey of the United Kingdom. 499pp.
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Wright
, V.P. 1985. Seasonal banding in the alga Solenopora jurassica from the Jurassic of Gloucestershire, England. Journal of Palaeontology, 59, 721-732.
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2.8 TOPICS - Portland Building Stone and Quarrying
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Anonymous
, 1962. The Quarrying of Portland Stone. Reprinted from the Quarry Managers' Journal, June, 1962, 8 pp.
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Howe
, J.A. 1910. The Geology of Building Stones. Edward Arnold, London. 455 pp.
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Lang
, J. 1956. Rebuilding St. Paul's after the Great Fire of London. Oxford University Press, Oxford [not yet seen - recommended by Tom Williamson as the best account of how stone was quarried for the rebuilding of London after the Great Fire]
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Leary
, E. 1983. The Building Limestones of the British Isles. Department of the Environment, Building Research Establishment. London, Her Majesty's Stationery Office, IBSB 011671365 8, 91pp.
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North
, F.J. 1930. Limestones: their Origins, Distribution, and Uses. Thomas Murby and Co., Fleet Lane, London. 467pp.
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Pushman
, D. 1987. Precious Stone of Dorset. Dorset Publishing Company, Sherborne, Dorset. 128 pp. ISBN 0 90212993 7
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Trim
, P. 1991. The Quarrying of Portland Stone. Isle of Portland Heritage Trust, 22 pp. including map. By Peter Trim, Isle of Portland Heritage Trust (obtainable at at the Chesil Beach Centre). [Useful information on the history of quarrying of Portland Stone, with several old photographs.]
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2.9 TOPICS - Purbeck of the Isle of Portland
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Bosence
, D.W.J. 1987. Mesozoic platform carbonates and benthic calcareous algae of the Severn and Wessex Basins. In: 4th International Symposium on Fossil Algae, Cardiff, July, 1987, edited by Robert Riding. Pre-Symposium Field Excursion, Excursions Guide, pages unnumbered. See section: Portland and Purbeck Formations of the Isle of Portland. End-Jurassic regressive sequence with oncoids, oyster/Solenopora reefs, trees, palaeosols and tufas.
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Damon, R. 1884. Geology of Weymouth, Portland, and Coast of Dorsetshire, from Swanage to Bridport-on-the-Sea: with Natural History and Archaeological Notes. New and Enlarged Edition (2nd Ed.), Weymouth, R.F.Damon, London, Edward Stanford. 250p
.
Francis
, J. E. 1983. The Fossil Forests of the Basal Purbeck Formation (Upper Jurassic) of Dorset, Southern England: palaeobotanical and palaeoenvironmental investigations . Unpublished Ph.D. Thesis, University of Southampton. 295 pp. By Dr. Jane Elizabeth Francis, now at Leeds University. Abstract: During the Upper Jurassic, coniferous forests grew adjacent to the Purbeck evaporitic basin in Dorset: The palaeobotany of the forests is described for the first time and the Purbeck forest environment reconstructed. The basal Purbeck Formation of Dorset was deposited during minor transgressive and regressive phases on the borders of a shallow hypersaline basin. The sediments include evaporites, hypersaline intertidal algal stromatolitic sediments and lagoonal pelletoid silts interbedded with supratidal algal mat sediments. The unusual features are brecciated calcrete and calcareous marls representing former forest soils. The trees which grew in the rendzina-like palaeosols of the Lower and Great Dirt Beds are now preserved in situ as silicified tree stumps and branches. They were drowned by rising hypersaline water and preserved within mounds of algal stromatolitic sediment. The wood was rapidly silicified by length-slow chalcedony (quartzine), a type of silica commonly associated with evaporitic environments. The fossil forests were dominated by one type of conifer belonging to the extinct family Cheirolepidiaceae. The wood of this is designated Protocupressinoxylon sp. A nov., the small scale-like leaves are Cupressinocladus valdensis (Seward) Seward and the small male cones Classostrobus sp. Alvin, Spicer and Watson. The tree is a source of Classopollis Pflug pollen so widespread in the Jurassic. A reconstruction of this Purbeck tree, based on evidence from fossil remains, is presented. The trees were monopodial with low branches and shallow spreading roots and formed fairly dense, closed forests. A few other conifer species were also present but much less abundant and cycadophytes (Bennettitales) are also represented by their silicified stems. The miospore assemblage from the palaeosols is dominated by Classopollis pollen (70% of samples), but also represents a rather poor flora of filicalean and lycopsid plants. Comparison with modern tree-ring data from semi-arid regions suggests a Mediterranean-type of climate for the Purbeck with warm, wet winters and hot, dry summers. The markedly seasonal nature of the climate is supported by sedimentary and faunal evidence such as ephemeral lake sediments containing both a freshwater fauna and flora plus evaporites. Modern analogues to the Purbeck environment have been found in the Mediterranean areas of the southern parts of Australia. The environment of the Callitris forests of Rottnest Island, Western Australia, appears remarkably similar to that of the~Purbeck forests. This type of seasonal, semi-arid climate during the Upper Jurassic accounts for the paradoxical association of evaporites with well developed forest vegetation. It contrasts with the widely held view, that the Jurassic climate was warm and equable. The reconstruction of the Purbeck trees and forest environment may serve as a model for other Upper Jurassic and Lower Cretaceous vegetation.
Francis, J.E. 1983b. The dominant conifer of the Jurassic Purbeck Formation, England. Palaeontology, 26, 277-294. Abstract: Fossil trees are preserved in situ in fossil soils in the Lower Purbeck (Upper Jurassic) strata of Dorset. Silicified tree stumps, still rooted in the soils, stand erect and protrude into the overlying limestones. Numerous trunks and branches lie on the soils, which also contain conifer shoots. The forests were dominated by one kind of conifer with wood, named here as Protocupressinoxylon purbeckensis sp. nov., foliage belonging to the species Cupressinocladus valdensis (Seward) Seward and with male cones yielding Classopollis pollen. A reconstruction of the anatomy and habit of the tree is given. The Lower Purbeck palaeoclimate is discussed using the evidence of tree growth rings and the character of the associated sediments.
Francis, J.E. 1984. The seasonal environment of the Purbeck (Upper Jurassic) fossil forests. Palaeogeography, Palaeoclimatology, Palaeoecology, 48, 285-307. Abstract: In the basal Purbeck Formation of Dorset a paradoxical association of evaporites and fossil forest vegetation is found, representing well-developed gymnosperm forests which grew on the borders of the shallow, hypersaline Purbeck lagoon which covered southern England during the late Jurassic. The dominant tree was a cheirolepidiaceous conifer which appears from its morphology to have been adapted to growing in a semi-arid environment. The narrow and variable growth rings of the trees indicate that conditions were marginal for tree growth and highly irregular from year to year. Comparison with modern tree-ring data suggests that the Purbeck climate was of Mediterranean type, with warm wet winters when the trees were able to grow but with hot, arid summers suitable for the formation of evaporites. The seasonal nature of the climate is also reflected in adjacent sediments, including a clay containing both fresh-water fossils and evaporites, calcrete crusts in the palaeosols, the nature of the silicification and the presence of seasonal crustaceans in finely laminated shales. Analogous modern environments for both the forests and the seasonal lagoonal sediments can be found in the Mediterranean-type climatic regions of South Australia. This evidence shows that within the "equable" Jurassic climate marked seasonal variations affected the whole environment. The seasonal nature of this climate supports recent palaeoclimatic models which propose that such a climate prevailed along mid-latitude continental margins during the Mesozoic.
Francis, J. E. 1986. The Calcareous Paleosols of the Basal Purbeck Formation (Upper Jurassic) Southern England. p. 112-138 in: Wright, V.P. (Ed.) Paleosols: Their Recognition and Interpretation. Blackwell, Oxford. ISBN 0-632-01336-2. By Dr. Jane Francis of Leeds University. Summary: Rendzina paleosols are preserved within a sequence of marginal continental deposits of algal stromatolitic and pelletoid limestones, constituting the basal part of the Lower Purbeck Formation in Dorset. The Great Dirt Bed is the most well-developed paleosol exhibiting a characteristically simple A/C rendzina profile, consisting of a dark organic-rich horizon overlying limestone bedrock. The main component of the matrix of the A-horizon is decomposed plant debris. There is little evidence of the activity of soil organisms and a notable absence of a pelletoid moder fabric, the faecal pellet textures typical of modern rendzinas. The upper O-horizon of undecomposed plant litter is also lost. This soil supported a conifer forest of slow-growing shallow rooted trees, now preserved in situ as silicified tree trunks and carbonized roots. Pebbles derived from the underlying limestone are incorporated in the soil matrix. Some consist of blackened sediment derived from a desiccated and fractured organic-rich deposit previously formed on the margins of the adjacent lagoon. The semi-arid, seasonal Purbeck climate promoted the formation of laminated and mottled deposits of secondary carbonate or calcrete, present as micritized bedrock, laminar rinds and cement around pebbles. This was itself brecciated by the soil processes and probably also by the mechanical action of the tree roots, then to become incorporated into the solum as pebbles. The Lower and Basal Dirt Beds are immature forms of rendzinas, with similar simple profiles of organic-rich layers with high carbonate content, overlying marl and devoid of large pebbles. The Lower Dirt Bed also supported a forest of conifers and cycadophytes. Each paleosol is capped by algal limestone, which originated as algal-bound sediment formed when rising saline lagoon water successively inundated the forests. This covered the tree stumps and the top of each soil with a protective layer of sediment, ensuring the rather exceptional preservation of these paleosols with in situ tree stumps. [Key paper on the Basal Purbeck Dirt Beds of Lulworth and Portland.]
Francis, J. 1996. Paddling in the Portlandian: a new record of dinosaur footprints from the Purbeck/Portland transition, Portland. Palaeontological Association Newsletterr, No. 32. Abstracts and Programme for the 1996 Annual Meeting (40th). Edited by Smith, P.M. and Thomas, A.T., 1- xxxii + 12pp. One paragraph only (as below) on page xv of the Abstracts volume. "A new set of dinosaur footprints has been discovered on the Isle of Portland on an exposed bedding surface in a disused quarry. The footprints are shallow impressions of small (up to 14 cm in length broad three-toed prints, very similar to those made by bipedal tridactly ornithopods such as Iguanodon . They do not appear to form a distinct trackway, more of a meandering stroll assemblage. The footprints occur in the upper surface of a transitional bed between the underlying marine shelly oolites of the Portland Stone Formation and overlying palaeosols and algal limestones of the Purbeck Lulworth Formation. This bed represents a change from high energy carbonate shelf facies to shallower, lower energy conditions prior to the onset of terrestrial soils/hypersaline lagoon environments. This is the lowest stratigraphical occurrence of footprints known in the Purbeck Group, since previously recorded footprints occur much higher in the Middle Purbeck Durlston Formation. These footprints show that ornithopod dinosaurs paddled happily in the shallows of the Portlandian seas in the Mediterranean climate that prevailed at that time." End of Abstract. By Jane Francis, Department of Earth Sciences, University of Leeds, Leeds, LS2 9JT. [The location is believed to be a small abandoned quarry of Portland Stone with basal Purbeck Caps and Dirt Beds above Freshwater Bay, on the east cliffs of Portland, map reference 691702, but nothing is very obvious there at present. The bed is the Transition Bed, a thin and laminated pelletoidal limestone, characterised in many places by a fauna of small lagoonal gastropods, such as Hydrobia as moulds and with some foraminifera visible in thin-section. It is fused directly to the top of the Portland Freestone which is characterised by the shells of large marine molluscs.]
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Jarzembowski
, E.A. and Coram, R. 1997. New fossil insect records from the Purbeck of Dorset and the Wealden of the Weald. Proceedings of Dorset Natural History and Achaeological Society, for 1996, vol.118, 119-124. Authors' Abstract: This paper updates the checklist (Jarzembowski, 1993) and subsequent articles (Clifford et al., 1994; Coram et al., 1995) in previous Proceedings. Recent discoveries are reviewed and Purbeck fossil insects collected by the Revd O. Fisher last century and deposited in the Sedgwick Museum, Cambridge, have been re-examined. Some groups are traced through the non-marine Lower Cretaceous of southern England. (End of Authors' abstract). [Bugs, flies etc from the Middle Purbeck of Durlston Bay and dragonfly larvae from the Lower Purbeck of Durlston Bay and Freshwater Bay, Portland.]
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Webster
, T. 1826. Observations on the Purbeck and Portland Beds. Transactions of the Geological Society of London, Series 2, 37-44.
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West
, I.M. 1960. On the occurrence of celestine on the Caps and Broken Beds at Durlston Head, Dorset. Proceedings of the Geologists' Association, 71, 391-401. Abstract: An occurrence of celestine in the Lower Purbeck Beds at Durlston Head is described and shown to be of syngenetic origin. Deposition probably took place near the margin of a basin of evaporite deposits into which strontium solutions were introduced. At a later date the celestine has been involved both in the brecciation that formed the Broken Beds and in complex local faulting. [This record of strontium minerals was the first definate evidence of former evaporites in the Broken Beds. It supported the hypothesis of Hollingworth (1938) that gypsum or anhydrite were once present at this horizon. The precise origin of the celestite, however, was not well-understood at that time, and it was later shown to be a replacement of evaporites (connected with groundwater flow up the fault-plane) and not syngenetic. See West (1973; 1975). The cliff section (fig. 2) is of a downbulge into former evaporites, and is a relatively complex part of the Durlston Bay cliffs that is not easily interpreted at first sight. Two celestite horizons are present, but the palaeosols of the Lulworth area are not properly developed here because this locality is in the "basinal" facies of the Purbecks. Since this paper was written celestite has been found in the Purbecks in the Soft Cockle Member of Durlston Bay and the Isle of Portland, in the Caps and Broken Beds at Worbarrow Tout and at Stair Hole. Calciostrontianite also occurs at Durlston Head (Salter and West, 1965).]
West, I.M. 1964a. Evaporite diagenesis in the Lower Purbeck Beds of Dorset. Proceedings of Yorkshire Geological Society, 34, 315-330. [Petrographic evidence of vanished evaporites in the Caps and Broken Beds - pseudomorphs, celestite, lutecite etc. Diagenetic history established.] Abstract: Five stages have been determined in the diagenetic history of the calcium sulphate beds of Lower Purbeck age in Dorset, particularly by reference to abundant pseudomorphs and other relict textures and structures preserved in late-formed gypsum and in secondary silica and calcite. The weight of the overburden is thought to have controlled the changes. Occurrences are described of minerals, including celestite, calciostrontianite, lutecite and quartz remaining after the removal in solution of gypsum. A description is also given of secondary limestones which occur particularly in the Caps and Broken Beds. They are shown to be almost entirely replacements of original sulphate deposits.
West, I.M. 1965. Macrocell structure and enterolithic veins in British Purbeck gypsum and anhydrite. Proceedings of the Yorkshire Geological Society, 35, 47-58.
West, I.M., 1969. Contribution in International Field Symposium on the British Jurassic; Guide for Dorset and South Somerset. Ed. H.S. Torrens, A60-61.
West, I.M. 1973. Vanished evaporites - significance of strontium minerals. Journal of Sedimentary Petrology, 43, 278-279. [On indicators of former evaporites such celestite and associated lutecite, the oblique-extinguishing variety of chalcedony; also length-slow chalcedony - quartzine etc.] Extracts: 'In a recent paper, Folk and Pittman (1971) have clearly indicated the importance of lutecite and quartzine varieties of chalcedony as evidence for the former presence of evaporites. Although lutecite has been successfully employed by the present writer for the detection of former gypsum deposits removed by dissolution (West, 1964; West, Brandon and Smith, 1968), confirmatory evidence is usually necessary. Fortunately, those processes which cause the removal of evaporites in solution frequently also result in their partial replacement by other minerals. Groundwater with bicarbonate ions may partly convert calcium sulphate deposits to calcium carbonate before dissolution of any remaining gypsum. Examples of such calcitised evaporites have been described by West (1964), Shearman and Fuller (1969) and other authors. In a dolomitic succession the calcitic nature of such replacements may be conspicuous. Pseudomorphs, relics of anhydrite in euhedral quartz crystals, and traces of net-texture (West, 1964) or nodular structure (West, 1965) may be present in any replacements or residues of dissolved evaporites. A positive indication of the former presence of calcium sulphate is the occurrence of celestite. This mineral is rarely found in sedimentary deposits other than evaporites, replaced evaporites or insoluble residues of evaporites. The related mineral barite is not so restricted. Associations of celestite with present or former evaporites have been described by Lacroix (1897), Zaritsky (1961), West (1964), West, Brandon and Smith (1968) and many other authors. Celestite is, in most cases, formed by the replacement of gypsum or anydrite; it is much less soluble than those minerals. It is usually formed by the selective removal of strontium ions from groundwater by reaction with deposits of calcium sulphate. Water containing a large proportion of calcium ions and a small proportion of strontium ions most commonly exists where limestone deposits occur in proximity. Celestite beds of appreciable thickness may be thus formed, particularly at the upper and lower boundaries of gypsum or anhydrite deposits. Such diagenetic formation of celestite is most favoured where there is appreciable flow of groundwater. Continuing diagenesis in a bicarbonate-rich environment may convert celestite to calciostrontianite (Salter and West, 1965). Smaller scale occurrences of celestite may be produced by a similar mechanism where gypsum veins have penetrated into limestone... Thus, there are many criteria for indicating the former presence of evaporites and it is wise to employ at least two. The occurrence of strontium minerals together with length-slow chalcedony [and/or lutecite] provides reliable evidence for the former presence of evaporites.'
West, I.M. 1974. Evaporite diagenesis in the Lower Purbeck Beds of Dorset. Reprinted in Kirkland and Evans (Ed.): Marine Evaporites, Origin, Diagenesis and Geochemistry. Benchmark Papers in Geology. [See West, 1964]
West, I.M. 1975. Evaporites and associated sediments of the basal Purbeck Formation (Upper Jurassic) of Dorset. Proceedings of the Geologists' Association, London, 86, 205-225. Abstract: Four facies of limestones, each with particular contents of calcitised evaporites and of skeletal debris were recognised. They are compared with sediments of modern evaporite-depositing environments. The lowermost limestones, stromatolitic and pelletoid with foraminifera, probably originated in intertidal to shallow subtidal, moderately hypersaline, water. Overlying pelletoid limestones with algal-mats and some gypsum are products of high-intertidal flats. The main evaporite beds were originally gypsum, probably formed in supratidal to intertidal, very hypersaline, palaeoenvironments. The gypsum was converted to anhydrite and later brecciated in part, forming the Broken Beds. Extensive calcitisation produced porous unfossiliferous limestones. Ostracodal limestones above probably originated in shallow, only moderately hypersaline water. All the basal Purbeck strata were formed in and around a large shallow gulf with extensive tidal flats and with water of varying but predominantly high salinities. At times of uplift, thin soils developed on the former margins of the gulf. Forests were able to exist there because, although the area was within the semi-arid zone, it was probably very near to the boundary of the warm-temperate zone. End of Abstract. [Additional notes on topics discussed: Palaeosalinity origins of the basal Purbeck facies and lateral correlation. Mostly hypersaline to varying extents, including the stromatolite horizons. Fossil trees 'pickled' in a salt lake. Details of the basal Purbeck strata at all the main localities, studied petrographically. Depositional environments of the dirt beds and marls. Palaeoenvironmental significance of sedimentary cyles. Thickness variations of the facies. Relationship of the Broken Beds to the evaporitic facies. Local uplift. Penecontemporaneous fault movement. The Mupe Bay oil sand. Perryfield Quarry succession on the Isle of Portland.]
West, I.M. 1979a. Sedimentary Environments and Diagenesis of Purbeck Strata (Upper Jurassic - Lower Cretaceous) of Dorset, U.K. Unpublished Ph.D. Thesis, Southampton University, 181 p. Abstract: Twelve papers, notes and a contribution to a book, all either published or accepted for publication, constitute this thesis. All parts of the classic, shallow-water, schizohaline Purbeck Formation of the type area are discussed but emphasis is on Lower Purbeck evaporites. Diagenesis of these involved much conversion of initial small lenticular crystals of gypsum to anhydrite with net-texture. The anhydrite was extensively replaced by calcite and celestite in the Broken Beds, a tectonic evaporite breccia at the base of the Purbecks. Evaporites were almost completely lost in solution from this breccia leaving characteristic relics of "vanished evaporites". Elsewhere, in the more argillaceous parts of the formation the sulphate remains, mainly as porphyrotopic secondary gypsum. Nodules and enterolithic veins are abundant in both the calcium sulphate and in the replacements. The similarity to those in Holocene sabkhas of the Trucial Coast (Shearman, 1966) suggested an origin on supratidal sabkhas, but there is a lack of desert sediments and instead the evaporites are interbedded with forest soils. Analogous Carboniferous evaporites show evidence of sabkha origins but no sign of desert conditions [West, Brandon and Smith, 1968. A tidal flat evaporitic facies in the Visean of Ireland. Journal of Sedimentary Petrology, 38, 1079-1093.]. New evidence has come from sabkhas in Northern Egypt where gypsum nodules develop in partly vegetated environment, dry but not excessively so, and supports other evidence for a semi-arid origin for the Lower Purbeck evaporites [West, Ali and Hilmy. 1979. Primary gypsum nodules in a modern sabkha on the Mediterranean coast of Egypt. Geology, 7, 354-358.]. The relatively dry climate was temporary and facies of higher parts of the Purbecks seem to result from sub-humid conditions. Throughout the formation lagoonal, 'intertidal' and supratidal deposits can be recognised but in the Middle and Upper Purbecks the lagoonal sediments have abundant brackish shelly faunas and, there, 'tidal-flat' deposits consist of shell-sand with dinosaur footprints but usually without evaporites. Progressively the proportion of land-derived clastics such as kaolinite and quartz sand increases as the continental Wealden is approached and final Purbeck sediments contain debris eroded from the underlying Portland Stone Formation, then uplifted at the western margin of the basin.
West, I.M. 1979b. Review of evaporite diagenesis in the Purbeck Formation of Southern England. In: Symposium on: Sedimentation Jurassique W. European. ASF Publication Speciale, No. 1, 407-415.
[text location: Portland Bibliography - end of West references]
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Whitaker
, W. and Edwards, W. 1926. Wells and Springs of Dorset. Memoirs of the Geological Survey, England. H.M. Stationery Office, 119 plus xi pp.
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Wimbledon
, W.A. 1987. Rhythmic sedimentation in the Late Jurassic-Early Cretaceous. Proceedings of the Dorset Natural History and Archaeological Society, 108 for 1986, 127-133. Most of this paper is on the Portland Group. An Appendix refers to Purbeck nomenclature. Abstract: A number of shallowing and deepening phases is described in the late Kimmeridgian - Berriasian interval. Eleven deepening / transgressive events are noted in the most complete Dorset section. A preferred lithostratigraphy for these beds is compared to previous lithostratigraphy, and "event correlations" are critically examined.
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Ordnance Survey,
Map 1:25,000 Weymouth and Portland, Sheet SY 67/77, Pathfinder 1343 (see also 1:10,000 map).
2.11 TOPICS - Maps, Geological
(Flat or folded copies geological maps can be ordered from the British Geological Survey).
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British Geological Survey. 1974. 1:50,000 geological map - Weymouth, Sheet 342. [This covers Weymouth and Portland with Lulworth Cove in central part (a large part of this map is sea, the geology of which is not shown). It extends from west of Weymouth to east of Kimmeridge and northward to Winfrith Newburgh. This map, based on a survey of 1896, is quite reliable and is easier to read than the new 2000 West Fleet and Weymouth Sheet (see House (2001) ). However, the new map is useful as a supplement.]
British Geological Survey. 2000. Geological Map: West Fleet and Weymouth. 1:50,000 Series, England and Wales Sheet 341 and part of sheet 342. Solid and Drift, with seafloor geology, cross-sections and other data. New map. [This commences just to the west of Durdle Door, Lulworth and includes Bats Head. It extends from here westward to Abbotsbury, including all the Fleet Lagoon and the Isle of Portland. It provides a cover of most of the Weymouth Anticline. The continuation southward onto seafloor geology is something that the previous Weymouth and Fleet maps do not have. There are large, north-south cross-sections based on boreholes and seismic data. These show deep faulting and such features of interest as the thickness and distribution of evaporites in the Permo-Trias. It has good structural contour maps for the top Penarth Group and the top Corallian and other information, such as sea-floor sediment data for the offshore area around Weymouth and Portland.
There are clearly different views on this map. It has been favourable reviewed by David Nowell (2001). Although this new Weymouth map certainly provides some new details, particularly in terms of members, there are also, unfortunately, some problems (which one hopes will be corrected in later editions). Some of the defects have been discussed by House (2001) . Most easily seen, and most affecting the coastal geology, are anomalies in outcrop and symbols in the offshore around Bats Head to White Nothe. The offshore rocks of Portland Stone at Bats Head, the Cow and the Calf have been placed not in a Portland outcrop but in the Chalk Group. As Professor House (2001) House pointed out their Portland Stone composition has been known since 1818. Indeed, in the past the Geological Survey has always described them correctly. The matter will not be discussed further here.
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Webpage - written and produced by:
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Ian West, M.Sc. Ph.D. F.G.S.