INTRODUCTION:

Topographic Maps

INTRODUCTION:

Aerial Photographs

INTRODUCTION:

Geological Maps INTRODUCTION:

Geological Maps

The British Geological Survey map, 1:50,000, Solid and Drift, 2000 Edition, Swanage Sheet, 343 and part of 342, is well worth purchasing. It can be obtained from the British Geological Survey website and is very inexpensive, costing only 12 pounds sterling.

This map is based on Nowell (1997). It is very good and it is recommend that the original paper be consulted for further details. It is particularly useful in not only showing the general geology but also revealing the details of faults in this area. The north-south distance of the Portland Stone from the Chalk varies greatly along this stretch of coast and the reasons are clearer if the details of the fault pattern here is studied.

LOCATION:

Approach from Lulworth Cove (from the east)

From Lulworth Cove the walk to Durdle Door follows a convenient path obliquely up the side of Hambury Tout. The original chalk path has now been paved with limestone sets, having been subject to serious erosion by feet. An alternative means of access to Durdle Door is by driving to the Durdle Door caravan site beyond Hambury Tout, and walking from there.

Here we see the promonotory from the cliff-top when following the path over the hill from Lulworth Cove. The outer wall of vertical, Jurassic, Portland Stone (marine oolite) and basal Purbeck Caps (stromatolitic and pelloidal limestones) is obvious. This runs approximately east-west, but with some minor deviations in direction. Notice how the outcrop of the hard stone is shown not only by the outer walls of the promontory but also by outlying rocks. The main part of the lagoonal, Cretaceous, Purbeck Formation is recognised by the thin-bedded limestone and shale. It is not complete because it is truncated here by a fault. The hard Cherty Freshwater Limestone and the Cinder Bed (with oysters) in the Middle Purbeck are conspicuous as a double reef running east west. The Lower Cretaceous Wealden Group is of fluvial sands and clays with some lignite beds. This unit is also vertical and the softer beds have been eroded out by running water so that it is marked by a series of gullies. The grassy hollow to the north (inland direction) of the Wealden has been formed by an old mudslide of the Gault Clay (Upper Cretaceous). I do not know when this occurred but it has bushes within it but no trees. It is thus unlikely to be very old. The Upper Greensand is poorly exposed on this side.

Vertical to overturned Chalk is seen in the cliffs on the right-hand side of this photograph, that is to the north. Notice the interference effect of small waves coming through two gaps in the outer stone barrier. The beach is of subangular brownish granules of flint. It is similar to the beach material on the west side.

It is interesting that the beach material is mainly of flint granules, rather than pebbles as at Lulworth Cove. Is it of about the same particle size on both sides of the promontory in spite of differences in protection from storm waves, differences in fetch and differences in relationship to the prevailing wind.

LOCATION:

Durdle Door - the Natural Arch

The photographs above gives views of Durdle Door from different viewpoints (and at different dates). Both basal Purbeck limestone (with the stromatolites) and the top of the Portland Stone are involved in the wall of Durdle Door. The near-vertical Purbeck limestone is on the north, landward side. The more resistant Portland Stone forms buttresses on the far side against the southwesterly storm waves. The rock immediately beyond is the Bull, of Portland Stone, perhaps with some Purbeck limestone. There was probably once an extension of the stone wall to near this and perhaps an arch which collapsed long ago. In the distance in the left photograph is the small Chalk promontory of Bats Head, with the cave through it. This was probably once another Durdle Door type of headland, of which the limestone Cow rock offshore is a relic (there are photographs of Bats Head below). The central photograph, incidently is taken from the "neck" of soft Wealden sands and clays; the cracked slabs on the left of the photograph are of Purbeck limestone.

The natural arch of Durdle Door is one of the physical features of the area which has retained a name given to it probably more than a 1000 years ago (Arkell, 1947), showing that the coast does not change very rapidly. The name " Durdle " is derived from an Old English word " thirl " , meaning to pierce (as in " nostril "). A similar arched rock in south Devon is known as the Thurlestone. At Durlston Bay, Swanage, there was probably an arched rock of which a stack at Durlston Head (of Purbeck Broken Beds with celestite) is most likely to be the relic. Damon (1884) also mentioned another name: " The most singular feature of this is the natural arch, known as the " Barn-door ", formed in the Purbeck Limestone and sufficiently high for a good-sized sailing boat to pass through it "

The shape of the arch is largely controlled by two sets of joints at oblique angles. You can see these in some of the photographs above. Of particular interest are the structures here. The Purbeck Monocline plunges down to the east and here in the west we are near the very angular foresyncline. In this vicinity there is overturning which is not seen elsewhere and much strike faulting. Although there has been argument about the direction in which the incompetent strata moved here it could, in fact, only have gone up. There is no room beneath and there is an unconformity between the Jurassic and middle Cretaceous strata.

LOCATION:

The Arete of the Durdle Door Peninsula

The arete of the Durdle Door peninsula is formed by Cypris Freestones, thin-bedded ostracod limestones of the basal Purbeck Formation. They dip steeply northward, and have argillaceous units interbedded. There is a path on the top but it is dangerous away from the central grassy area, and very dangerous out to the far east or west. From the path there is a view down to the south of a steep, irregular limestone cliff, largely of Portland Freestone. To the north the Cypris Freestones continue down with some east-west minor folds.

LOCATION:

Man O' War Rocks and Cove

Man O' War Rocks and Man O' War Cove are east of the Durdle Door Promontory. The rocks are a continuation of the Portland Stone and the basal Purbeck Caps outcrop from Durdle Door. The most remarkable aspect is that these strata are too close to the Chalk outcrop in the cliffs for the sequence of strata between the basal Purbeck and the Chalk. Some substantial part of the succession must be lost by strike faulting. Because the Portland Stone runs into the unconformity at the base of the Gault and Upper Greensand at depth (to the north) any faulting must have been upwards. This is also true for the strike faulting, presumably similar that is seen in the Purbeck succession in the neck of the Durdle Door promontory. Upward strike faulting of Purbeck strata explains the Lulworth Crumples. They simply accomodate upfaulted Purbeck strata.

LOCATION:

Durdle Cove - Purbeck Formation - Caps

The stromatolites, mentioned above, have encrusted trees in a similar manner to those at the Fossil Forest. This is because Durdle Door is still on the Lulworth swell with soils and trees. Holes left by the rotted trees are visible. Viewed with binoculars from the mainland cliff the uppermost one is a hollow tube letting light through from the south (the sea). More study with binoculars or telescope is needed to identify all the tree-bearing stromatolites in this cliff. One or two of those shown in the image might prove not to be but some certainly are. Others will be found by careful observation (there may, for example, be another one left of the left-most red arrow). (Incidently, this is the only place that I know where seagulls nest in Jurassic trees!)

The upper part of Durdle Door photographed with telescopic lens from the Chalk downs to the north. The man, shown for scale, is returning from a very dangerous scramble on the narrow ridge over the door. Some of the stromatolites and tree holes can be seen quite clearly in this photograph. Some of the hole are more elongate vertically than horizonally, i.e. elongated on an original north-south axis.

Details of the outer pillar of the arch. The limestone forming the northern face here is of rounded masses of stromatolitic limestone, probably, as is usually the case, in pelletoidal limestone. I think that these are of the Soft Cap, i.e. above the Great Dirt Bed, not of the Hard Cap below it, but I have not approached this by boat. The position of the Great Dirt Bed is the critical factor here and I will try to determine the position of this in relation to this hummocky bed of the north face. It should be underneath, but I might be wrong. Using the figure for scale and assuming that his height is approximately 1.75m estimates can be made of the spacings of the trees. Only three of the tree positions, which seem very clear have been used. The spacings seem to average about 5.6m although this is only a very rough figure (try it yourself on the central image). A much more accurate study of this could be made and perhaps will be in the future. The trees at this site are small with trunk diameter of only about 25cm. This seems almost like a planted conifer forest of the type common in the New Forest of southern England, with quite close-spaced trees . Evidence elsewhere suggests relatively straight, upright trees of Cypris-type with wood of the genus Cupressinoxylon purbeckensis. See the papers of Jane Francis for more information. The Great Dirt Bed soil is not as well-developed here as at the Fossil Forest (this is nearer to the margin of the Lulworth peninsula) and was perhaps less favourable for large trees, although this argument depends on this particular tree horizon being above the Great Dirt Bed. These are just preliminary comments and more study of the Durdle Door fossil forest is needed; its situation makes it a rather difficult place to investigate although some more information will be added later.

Notice, incidently the solution effects by the sea on the limestone at the base of the pillar. The rather brownish-yellow colour of the rock in general is partly because of a fairly low and slightly reddish sun, the picture having been taken at about 7 pm. In direct and whiter light the Purbeck limestone is more of a buff colour.

Please be very careful of the cliffs around here. It is unnecessary to point out that no-one should try to cross the arch of Durdle Door. The cliff jumping shown in the picture is clearly not a safe activity, especially since there are submerged rocks at shallow depth in places. Particularly, do not try to climb any chalk cliffs in the Lulworth area (note that a rescue was taking place not far away while the right photograph was being taken). Most chalk cliffs are obviously impossible. But even in the few places where the slope is more moderate, chalk and grass has insufficient strength to hold you and sooner or later will come away in your hand. Grass on chalk cliffs is no guarantee of safety and can be very slippery, especially when wet. I know from some personal experience that chalk cliffs should not be climbed.

In the past, incidently, there were other risks on this coast. At least one fall from a cliff here was not an accident. On the night of 28th June, 1832, the Chief Officer of the Coastguard, Lieutenant Thomas Knight of Folkstone, was attacked by a band of smugglers near here. He was beaten before being thrown over the cliff near Durdle Door. He died on the following day (Legg, 1989).

LOCATION:

Durdle Cove - Purbeck Formation -Cypris Freestones

Ripple marks are present in the Lower Purbeck Formation at Durdle Door. These examples are from the Hard Cockle Member on the west side of the promontory close to the southern end of the beach and vertical limestone wall. You can also see excellent examples in the slightly older Cypris Freestones Member on the east side of the promontory. You can see that they are sharp crested and frequently bifurcate. In one photograph some (not necessarily all) bifurcations have been marked for clarity. You may see a few more on the image, and you will certainly find more in the field.

Such ripples conform to the descriptions of wave-formed ripples (oscillation ripples) (Tucker, 1982). These are formed by the action of waves on non-cohesive sediment, usually of medium silt to sand grades. They are typically symmetrical in shape (but not always). The crests of wave-formed ripples are generally straight and bifurcation is common , sometimes rejoining to enclose small depressions. In profile the troughs tend to be more rounded than the crests which can be pointed. The ripple index (wavelength over height) of wave-formed ripples is generally around 6 or 7. If you have time determine the ripple index of these.

The sediment here is a carbonate sand with some quartz. You will not see normal marine fossils. There are no ammonites, belemnites or large, thick-shelled bivalves. Fossils that you are likely to find are the small tests of ostracods (oval objects about 2 mm. in length). They are very abundant at some horizons. Look also for the shells (about 1 centimetre) of the " cockle " Protocardia . Fossil insect may also occur at about this horizon but are not easy to find. Protocardia purbeckensis is very common in the Lower Purbeck Formation. It probably occupied an ecological niche in the Purbeck environment much like that which the modern euryhaline (tolerant of various salinities) cockle, Cardium or Cerastoderma sometimes occupies. In Egypt it lives in moderately hypersaline lagoons, although it is dwarfed (West, Ali and Hilmy, 1983). There is evidence in this region for hypersalinity when these Lower Purbeck strata were deposited. Moulds of halite crystals occur at Worbarrow Tout and elsewhere, and in thin-section under the microscope pseudomorphs after gypsum crystals can be found. Although not present at Durdle Door beds of gypsum occur in the Soft Cockle Member above, further east.

The ripples, then, can be seen as evidence of shallow marginal conditions of a hypersaline lagoon, where small waves washed around the sediment. There are sediments casts of halite crystals here too. Dinosaur footprints can sometimes be found in facies like this but they have been seen here.

Higher in the Purbeck Formation look for the Cinder Bed with its numerous small oysters. It has a bluish grey appearance and is easily recognised once you have seen it. It represents more nearly marine conditions because echinoids have been found in it, notably by Professor Forbes in the 19th Century. Echinoids have no osmotic mechanism to survive non-marine salinities so they are important indicators of sea-water. They do not occur any other horizon in the Purbeck as far as is known because salinities were usually above or below those of sea-water and prone to fluctuate wildly in this extensive shallow lagoon. I believe that they fluctuated seasonally as well, so that the lagoon became very salty in the dry summer and halite was sometimes deposited from a lagoon that was almost fresh in the winter. One of the best horizons for study of Purbeck freshwater sediments is the Cherty Freshwater Limestone. It is easily found a short distance beneath the Cinder Bed. It is not very good for fossils here because it needs soil weathering and not sea erosion to bring out the silicified gastropods etc.

LOCATION:

Durdle Cove - Wealden

Proceeding northward (landward), and stratigraphically above the almost vertical, Purbeck strata, you will see the soft clays and sands of the Wealden Group. The steps down the cliff are on this. The unit is abnormally thin here but interesting. There is much black, lignitic, fossil wood which has come from conifer trees. It is compressed, friable and pyritic. The organic matter nourished sulphate-reducing bacteria which produced the sulphide ions; reaction with iron in the sediments produced the pyrite and surplus hydrogen sulphide may have given an unpleasant odour to the soils of the Wealden marshes and floodplains.

This is a possible locality for for dinosaur remains. They sometimes occur elsewhere in the Wealden with fossil wood. The bones are hard, brown and mineralised. They occur in the Dorset exposures (Swanage and Worbarrow) but are not as frequently found as in the Isle of Wight. I have only found one worn Iguanodon tooth, in the Wealden at Swanage.

LOCATION:

Durdle Cove - Gault and Upper Greensand

Next above (i.e. northward) comes dark grey, Gault Clay of the Albian Stage of the Cretaceous. It usually causes landslides and, as at other localities, there some collapse of the cliff. At the base of the Gault is a pebble bed which marks the transgression of the sea over the Wealden fluvial environments. The Gault can contain marine fossils but they are difficult to find unless the exposure is clean and unweathered. The Gault becomes more silty and sandy upwards and passes up into the Upper Greensand in a transitional manner.

Northward of the Gault, the west side of the Durdle Door peninsula has a good exposure of the Upper Greensand. One bed, as shown above, contains conspicuous Thalassinoides ichnofossil (burrows of decapods or crabs) cemented by calcite and protruding from the base of the bed. The hard projecting Exogyra Bed with Exogyra conica and Rotularia concava ( Serpula concava ) is easily recognised. The Chert Beds are also easily seen, although the chert is not black like the Portland chert but usually brown or grey. Sponge-spicules within it, with the aid of a hand-lens. Some of the Upper Greensand chert follows burrows. Notice the boulder bed just beneath the basement bed of the Chalk. The latter has small brown phosphate nodules, some replacing fossils such as small ammonites. Phosphatised ammonites can also been seen in the phosphate beds of the Upper Greensand. Look for a recess in the cliff in the Upper Greensand section and search for small brown or black phosphatised fossils in the softer more argillaceous units.

LOCATION:

Durdle Cove - Chalk Stratigraphy and Fossils

The Chalk of the Durdle Cove area is Lower Chalk, Middle Chalk and the lowest part of the Upper Chalk. The old terminology was in terms of the classic Chalk zones - Schloenbachia varians, Holaster subglobosus, Inoceramus labiatus, Terebratulina lata, Holaster subglobosus.. etc, etc. There is now, however, in addition a lithostratigraphic nomenclature of Mortimore and the British Geological Survey. If this terminology is used, some translation is needed. Thus a table is provided above to help with discussion of the Chalk.

It is necessary to have some knowledge of the fossils of the Chalk that are used for zoning. Thus some basic fossil illustrations are given below.

Echinoids occur in the chalk here, usually Micraster but the specimens are usually abraded through by sea erosion and only an outline of the thin test is visible. Some examples of Cretaceous echinoids are shown in the illustration above.

LOCATION:

West of Durdle Door - Durdle Cove Chalk

Beyond, in a north-westward direction, is Lower Chalk of Cenomanian age. This is, as usual, cyclically banded but it is very sheared here. Next comes the conspicuous unit of marl - the Plenus Marl, which is also very sheared with conjugate shears. It is well-exposed in a recess as shown in a photograph above. Middle Chalk follows in the younging direction, to the north, and it is mainly nodular and without flints.

LOCATION:

Durdle Cove - Plenus Marl and Sheared Chalk

Vertical Chalk and Upper Greensand in Durdle Cove is shown here in a fairly recent photograph and in an old photograph of Rowe and Sherborn (1902). Notice the plenus Marl in both photographs. The bearded gentleman in the old photograph (who is it - Dr Arthur Rowe?) with the black leather gaiters and stick is pointing to the Chalk Rock of the Geological Survey. This is a band of yellowish nodules, a conglomeratic horizon, usually glauconitic but here oxidised to a yellowish colour. Note the uppermost bed of the Upper Greensand forming a prominant wall, and to the left (stratigraphically above) the phosphatic basement bed of the Chalk. Note that the Lower Chalk has been placed by Rowe entirely in the subglobosus zone. The plenus marl at the top of the Lower Chalk has been displaced northwards by a small thrust fault.

LOCATION:

Durdle Cove - Thrust Plane in the Chalk

Chalk cliffs west of Durdle Door. The cliffs mainly consist of vertical Middle Chalk with some flints. The thrust plane of Durdle Cove is conspicuous (Arkell, 1947, p. 289) and has some fault breccia above it. This is near the junction of Middle and Upper Chalk. The slide plane or shear plane (classified by Arkell, 1938, as belonging to group 3a) dips south at various angles between 0 and 20 degrees. The hanging wall (the part above the fault) have moved north by up to 4 metres (Strahan, 1898) and there is a fault breccia of up to a third of metre in thickness. The sea has eroded the fault plane into a series of caves. You can see that it does not continue west of the embayment where the dry valley of Scratchy Bottom comes down to the sea. It is replaced by a number of smaller shears.

An old photograph from the classic work of Rowe and Sherborn (1902) showing the Chalk zones west of Durdle Door. The whole succession is Upper Chalk (or Ramsgate Chalk), with as mentioned above, the junction with the Middle Chalk (Seaton Chalk) near beach level. Annotations are based on those on an overlay of Rowe with minor modifications. Abbreviations are for the following zones.

Coniacian (lower part of Senonian)

M.ca. = Micraster coranguinum
M.ct. = Micraster cortestudinarium

Turonian

H.p. = Holaster planus (although Turonian this is part of the Upper Chalk and contains flints. This chalk is greyish)
T.lata = Terebratulina lata
Inoceramus labiatus

The Inoceramus labiatus and Terebratulina lata zones total 21 metres in Durdle Cove. Note that an older zone occurs in the upper part of the cliff. This is because the strata are overturned to some extent. Note also that the Terebratulina gracilis zone in Rowe and Sherborn's work has been replaced in this image by the more modern Terebratulina lata zone. The brachiopod Terebratulina gracilis actually only occurs in the upper part of the much higher Belemnitella mucronata zone according to Arkell (1947). A similar correction has been applied elsewhere where Rowe and Sherborn's photographs are used. The Inoceramus labiatus zone is seen in the eastern corner of Durdle Cove and is not clearly visible in this image.

There is clear increase in vegetation on the Chalk cliffs since 1902. Further comment is made on this elsewhere, but it is particularly obvious from these two photographs.

LOCATION:

Durdle Cove and Beyond - More on Structural Features

Bevan (1985) has provided a well-reasoned explanation of this and the numerous other shears of these cliffs. Sigma one, the maximum principal compressive stress, is near horizontal and there has been a net elongation parallel to the vertical layer-dip. Put into plain language, this means chalk has been squeezed from south to north, thinned in this direction and, in contrast, stretched out vertically. It is not surprising that this has happened near the foresyncline (the sharp bend of the fold), which intersects the coast at the inaccessible beach west of Bats Head. The proximity of the Portland Stone to the Chalk (but there are also other factors) and the faulting-out of parts of the Purbeck succession at Durdle Door ties in with this (to understand structures here, though, it is important to visualise the plunge of the monocline down to the east and to realise that what is seen near Durdle Door represents a much lower part of the fold in the Chalk than at Swanage or the Isle of Wight, and this lower part has a sharp bend)

LOCATION:

Scratchy Bottom

At the small embayment at the foot of valley of Scratchy Bottom, where there is usually a rough path up the cliff it can be seen that solifluction has moved the upper part of the vertical chalk southward. Material has slid down the valley in the periglacial conditions of the Pleistocene. Chalky head or hill wash is just visible as a brownish relic of this on the west side of the embayment. Elephant remains occur in similar material in a similar site on chalk in the Isle of Wight, but, as far as I know, they have not been found here.

Rowe (1902) studied the Chalk on the east side of the Scratchy Bottom. His photograph with his annotations (modified) is reproduced here by kind permission of the Geologists Association. The embayment shows overturned Upper Chalk of the Holaster planus zone, the Micraster cortestudinarium zone and the Micraster coranguinum zone. A band of yellow nodules separates the two Micraster zones. The Micraster cortestudinarium zone here consists of yellowish nodular chalk. This zone is 21 metres thick and fossiliferous. The zonal Micraster has been found. The Micraster coranguinum zone is not very fossiliferous but part of an ammonite of the leptophyllus group was found by Rowe at the head of the recess. This was quite an unusual discovery.

The slide plane shown here, effectively a small thrust to the north, is the same one that forms the line of caves in Durdle Cove.

LOCATION:

Swyre Head - High Chalk Cliff

A high Chalk promontory to the west of Durdle Door is Swyre Head. This is shown in recent years on the left and in 1902 on the right. This comparison is provided to show changes in the amount of vegetation on the cliff. It is obvious by comparing other old photographs with modern ones for this area that much Chalk has become covered in grass since 1902. I wonder why this is. If the rate of coast erosion has been constant then you would expect about the same amount of vegetation on the cliffs. Have the cliffs stabilised to some extent? Why should coast erosion reduce if the sea-level is rising more rapidly now, as it seems to be?

Have the cliffs retreated drastically at some time in the past, perhaps in the great storm of November 1703 with its south-westerly hurricane winds and the exceptionally high tides (Defoe, 1705). It is possible that clean white Chalk cliffs were produced then by a phase of erosion and that since that date erosion has been more moderate and grass has grown. This, however, is simply speculation and there is no specific evidence for this.

The cliffs west of Scratchy Bottom consist of the Micraster zones of the Upper Chalk (Coniacian - Micraster cortestudinarium , below, and Micraster coranguinum above. Micraster is the common heart sea-urchin of the Chalk, a creature which to some extent burrowed in the white mud of the sea-floor in late Cretaceous times. Good specimens are not easily found here, largely because the chalk is harder here than in most other areas (the intense local tectonics are responsible) and they do not break out easily but are cut through by erosion. Rather than look for the surface appearance of an echinoid, look for an oval cross-section with a thin shell. You should find examples. (In contrast, at Southampton University there were at one time very large numbers of good specimens of Micraster coranguinum in the Westlake Collection from the Micheldever (Hampshire) railway cuttings in the 1890s. An electrical driven machine was used to automatically clean them and this was done over a period of months.).

There are many shears in Swyre Head, the truncated hill in the middle of the image. Swyre Head presents a fine steep cliff about 90 metres high. The Chalk hill summits in the distance are rather higher, and are probably related to a peneplain at about 150 - 200 metres. The two dry valleys seen here may have formed Lulworth Cove type features in the past as the coast recessed (Jones et al. , 1984). The old coves have now coalesced and may be responsible for the stretch of open water between Durdle Door and Bats Head.

LOCATION:

Swyre Head - Platform of Marine Erosion

Swyre Head once projected further south and separated two bays. It has been eroded back so that this stretch of coast has been almost amalgamated into one bay. In the course of this the foot of the headland has been converted into a platform of marine erosion. The cliff is still being cut back with the consequence of falls of chalk debris from time to time. The Chalk is vertical here and has been cut across cleanly by marine erosion, revealing fossils and sedimentary structure in cross-section. The photograph was taken in April 2002 and this piece of coast is likely to show further changes in the future. Examine the old photograph of Rowe and observe changes at the foot of the cliff.

In this view to the southeast, the prominant offshore rock is the Bull, of Portland Stone. Not shown and directly to the south is a smaller, largely submerged Portland Stone rock, the Blind Cow which was part of an outcrop once affording some major protection to Swyre Head.

Looking rather like a giant, dark-coloured dinosaur is the Durdle Door promontory, with its Portland Stone outcrop. The offshore rocks continue from this.

LOCATION:

Butter Rock - a Chalk Stack

Further west, at the end of the beach is a chalk stack or pinnacle. It can also be seen in the Bats Head photographs below. The stack is small and aligned south of the small dry valley between Bats Head and Swyre Head. The bedding is vertical as shown by the lines of flints. Presumably the Chalk is here is planus Zone, as in the case of Bats Head.

A study of Bats Head and the Durdle Door promontory will help explain its origin. Look particularly at the photograph of Bats Head below to consider beach processes.

In one of the photograph above, taken towards the late afternoon sun and at low tide, notice the offshore Portland Stone rock, the Cow. This is the dominant limestone rock here and usually has cormorants or shags perching on it. It is part of a submerged ridge of Portland and Purbeck stone.

Similar chalk coastal features including stacks occur near Harry Rocks in the east of the Isle of Purbeck. Go to the Harry Rock webpage for comparative coastal features in near-horizontal Chalk.

LOCATION:

Bat's Head

For information on Bat's Head please go to the:

White Nothe to Bat's Head Webpage.

Chalk Cliffs beyond Bat's Head to White Nothe

The beach beyond Bats Head is not usually accessible except by boat but, as mentioned, is of particular interest in showing the foresyncline. You can, as I have done in the past, swum round Bats Head wearing geology boots and carrying a geology hammer, but this is not now recommended for safety reasons.

Please go to the: White Nothe to Bats Head geological field guide. (a new guide in preparation)

MISCELLANEOUS:

Dolphin at Durdle Door - 2002

On the 12 August, 2002, on the landward side of the natural arch of Durdle, tourists were swimming with a dolphin. The friendly dolphin, probably the one known as George, was spending hours playing with the children and adults in the water. A few pictures are added here for interest. At the time of his appearance at Durdle Door, the weather was warm (for England) and the water clean, clear and calm. He attracted many people to the beach and came into water quite shallow enough for children to wade in. Periodically he swum out towards the natural arch.

MISCELLANEOUS

Chalk Downs at Durdle Door - Soil and Vegetation

The short grass is usually grazed and grows on a thin calcareous soil. Water percolates underground through the chalk so the surface is usually relatively dry. Harebells, seen here in August, 2002, just northwest of the Door, are small blue flowers with joined petals and five lobes. The species is Campanula rotundifolia it is a member of the campanulaceae.

REFERENCES

Please go to the separate Lulworth Bibliography.

ACKNOWLEDGEMENTS

I thank the various students of Southampton University and London South Bank University for participating in field trips to Durdle and allowing photography for the internet. I am very grateful to the Geologists' Association to reproduce the photographs of Rowe. Dr Clive Needham and the Staff of Agip UK Oil Company are thanked for digital photographs of the area. Discussion with the late Professor Michael House has been very helpful. I thank Halfdan Carsten for his kind permission to use photographs taken on a field trip in Dorset in 2005. My wife Cathy has very kindly provided background support for the production of this and all the other webpages.