Safety

The main hazard at Hordle Cliff is of sinking into soft mud. It can be thinly covered by stones from the Pleistocene gravel or by some clumps of grass and then there is more risk of treading on it. In wet conditions it is wise to stay on the beach and collect from the lowest part of the cliffs.

There is a small risk of being struck by a falling rock, pebble or lump of mud. This risk is greatest where the cliff is steep and being actively eroded. Safety helmets are recommended where such risk exists.

Landslides are common in the area, especially in winter. Generally these do not move fast and are more of a hazard to property than to people. Where the cliff is steep, however, a rapid and, therefore, a more dangerous fall is possible and care should be taken.

There is more risk in standing close to the edge of the cliff than might be expected at a place with hard rock. The Plateau Gravel which usually caps these cliffs often stands as a vertical face that is not secure and may collapse at any time and, in particular, erosion can produce dangerous overhangs of gravel capped by soil and grass. Individual geological visitors and field leaders should make their own risk assessment and no liability is accepted.

INTRODUCTION:

Maps and Location

IINTRODUCTION:

Succession of Strata

The Headon Hill Formation (of the Solent Group) form part of the well-known Hampshire Basin, and is exposed at Hordle Cliff, west of Milford-on-Sea, in Christchurch Bay, and also at Headon Hill, the type locality near Alum Bay and Whitecliff Bay, in the Isle of Wight. The strata overlie the Becton Sand (Barton Sand) and Barton Clay. They are of Priabonian Stage of the Upper Eocene Series. In detail the strata at Hordle Cliff belong to the lowest part of the Headon Hill Formation - the Totland Bay Member. In terms of age in years these strata were deposited somewhere between about 38.6 amd 35.4 million years (Harland et al., 1982).

At Hordle Cliff there is a fascinating section of the Headon Hill Formation. It is mostly clay and marls with some sands, some ironstone nodules and very thin bed of limestone. Plant beds occur. Freshwater molluscs are abundant but remains of turtles, crocodiles, mammals, birds and even snakes are present.

From Hordle Cliff, with its excellent exposures of the Headon Hill Formation, there is a distant view of the Isle of Wight, shown here, somewhat enlarged. The Chalk cliffs, the stacks and the lighthouse are easily seen. These mark the southern boundary of the Hampshire (Tertiary) Basin. To the left of the Chalk are the vertical coloured sands of Alum Bay and to the left of those (actually to the northeast of them) is Headon Hill from which the strata of Hordle Cliff take their name. Hordle Cliff shows mainly the lower part of the Headon Hill Formation and has less limestone development than at Headon Hill. Vertebrate remain, particularly those of turtles, occur at both places but Hordle is better known for its important reptilian and mammal fauna.

GEOMORPHOLOGY:

Beach Features

This is a view at low tide on the 10 March of an offshore sand bar and a narrow lagoon extending from near the site of the sewer jetty at Becton Bunny, eastward past Taddiford and on to Hordle Cliff and Paddy's Gap from where the photograph was taken. It continues further towards Milford. It does not seem to have been present many years ago and may be related to the realignment of the coast here resulting from the development of an embayment east of the sewer jetty (now a promontory protected by rock armour).

STRATIGRAPHY- SUCCESSION

- General

The top left-hand diagram here shows the general succession of the Upper Eocene strata here with the major subdivisions indicated. The top right-hand diagram shows a medium level of detail in a vertical section by Tawney and Keeping (1883) . More detail and more recent information, with the use of modern palaeontological names, is available in a descriptive vertical section given by Edwards in an unpublished Ph.D. thesis. The photographs below show particular beds in the sequence which can be seen in the cliffs.

STRATIGRAPHY:

Succession

- Headon Hill Formation - General

The strata consist of soft marls, clays and sands with some plant beds, some ironstone and some thin, poorly lithified limestone. They contain abundant, thin-shelled bivalve and gastropod remains, mostly of freshwater and lagoonal origin. Gastropods like Viviparus and Galba resemble modern pond-snails. Brown bones occur, and these include the remains of crocodiles, snakes, birds and mammals. Fragments of turtle carapace are perhaps the most likely to be found. Charophyte algae and blackened seeds of Stratiotes, a lake plant like the "Water Soldier" are common. The variety of the strata in terms of lithology and colour (sometimes yellow or pinkish) and the rarity of typical marine shells clearly distinguishes these strata from the drab, blue-grey Barton Clay. They are the deposits of lakes, lagoons and swamps of Florida-type at the end of the Eocene.

STRATIGRAPHY - SUCCESSION

- Headon Hill Formation - Biostratigraphy

The cliff section exposes the Totland Bay Member, the lowest part, of the Headon Hill Formation. The following notes are based on Edwards and Daley (1997), whose publication provides an important, recent, restudy of the cliff section. The sediments were deposited towards the end of the Eocene, the Totland Bay Member belonging to the Priabonian Stage (38.6 to 35.4 My - million years - Harland et al., 1989) of the Upper Eocene. It lies between marine horizons assigned to calcareous nannoplankton zones NP 17 and NP 19/20 ( Martini, 1971, and Aubry, 1986) and has yielded a Late Eocene Euzet mammal assemblage (Cray, 1973). On the basis of revised mammalian taxonomy, Hooker (1987, fig. 1) assigned the lower part of the Totland Bay Member to the stehlini-depereti concurrent range zone and the uppermost part to the vectensis-nanus concurrent range zone. On the same basis Brunet et al. referred the Member to their Reference-Level MP17.

LOCATION:

Becton Bunny

(see also the main Barton webpage and the Barton coast erosion webpage )

A conspicuous feature of the coastal topography is the small stream valley of Becton Bunny which is very oblique to the coast. This was originally known as Beacon Bunny, as shown in a cliff section, above, by Charles Lyell (1829). It probably named after the adjacent Beacon Cliff which probably once had a fire beacon.

In Beacon Cliff is the junction of the Barton Group exposed and the Headon Hill Formation. Becton Bunny is a convenient boundary and is an interesting place for major coast erosion at the eastern end (down-drift) side of the Barton sea defences. It is a place of terminal scour and of cleanly eroded cliff sections. There is easy access to the cliff top here from a car-park at the eastern end of Barton overcliff drive (western end of the golf course). The map reference is SZ 245928. Provided the coast path is not broken by erosion (and this is inevitable sooner or later) there is also access from Taddiford Gap, discussed below. The beach at Becton Bunny can be reached by walking from the main beach access at Barton-on-Sea (further west) or from Taddiford Gap, or, if the varying state of the cliff permits, scrambling down at the Bunny (probably inappropriate for a party).

Becton Bunny, incidently is an example of the chines which are developed in relatively soft strata on the coast of Bournemouth and the Isle of Wight. They are small steep-sided ravines incised into broader valleys. This incision is the result of rapid retreat of the coast so that the stream has become rejuvenated and cut down to adjust to the new cliff location. Unfortunately this particular chine is doomed to disappear in a while by the very rapid coast erosion, leaving just the upper valley, which extends across the golf course.

Examine these two photographs taken just over a year apart (September 2002 and October 2003). A steep or overhanging section of Pleistocene flint gravel is at the top. This is above sands and clays which mostly belong to the Becton Sands (Barton Sands) of the Barton Group (i.e. above the Chama Member and Barton Clay). The sands and clays are being rapidly eroded by the sea with some collapse and slumping. The cliff is unstable, oversteepened and retreating and it is important to keep away from the edge, which is often overhanging. There has been a bite-like retreat of the cliff-top in the year and erosion is moving rapidly in the direction of the Becton Bunny valley. The seats and path here clearly will not last for more than a few years.

The above photograph was taken in March 1998. The dark object seen projecting into the sea is the remains of a large sewer pipe, no longer in use at that time. In the 1950s from here to Becton Bunny the atmosphere was badly tainted by sewage odour, although if I recollect correctly seagulls were attracted to the offshore outfall. The pipe has formed a partial barrier to beach transport in recent years (previously the beach was further out and gravel could travel past it). Since the erosion has increased in this vicinity with the construction of the Barton sea-defences it has been reinforced with blocks of limestone so as to form the most easterly strongpoint of the Barton area. This is a barrier to the easterly long-shore drift. Thus with limited, protective, beach shingle available to the east of it a new embayment has been created and this continues to be eroded.

This photograph was taken in October 2003. The remains of the pipe seem to have gone and there has been some erosion of the promontory. The coast still projects because the strongpoint gives protection. There is still increased erosion to the east (down-drift) of this strongpoint and there seems to be some detectable affect on the coast from here to Taddiford Gap. The enhanced coast erosion has provided a good exposure of the upper part of the Becton Sand Formation (Barton Sands). The black Lignite Beds (L), which are at the top of the Becton Sand, are easily recongnised features. These lie beneath the basal part of the Headon Hill Formation ( Mammal Bed etc) and descend in the cliff eastward towards Taddiford Gap where they are near the beach level. Thus, to the east of here the lower part of the Headon Hill Formation descends and eventually, at Hordle Cliff east of Taddiford Gap, comes to occupy almost all the cliff.

Beacon Cliff, East of Becton Bunny

- Introduction

Beacon Cliff is an actively eroding cliff between Taddiford Gap (Long Mead End) in the east and Becton Bunny (original name - Beacon Bunny) in the west. Because of the obliquity of Becton Bunny and appreciable cliff erosion this cliff has lengthened from east to west with time. In the early 19th century it quite short, as shown in a cliff section by Charles Lyell (1829), because Taddiford Gap and the mouth of Becton Bunny (very oblique to the coast) were quite close. The prominant headland between the two valleys, easily seen from the Isle of Wight and elsewhere, was probably a good place to site a warning fire beacon in the 18th century or a little earlier. This cliff probably did not exist, however, in the 16th century because at that time Long Mead End and Becton Bunny would probably have been joined.

LOCATION - STRATIGRAPHY:

Beacon Cliff -
Bed J - Becton Bunny Bed - Clay ("Oliva branderi Zone")

LOCATION - STRATIGRAPHY:

Beacon Cliff - Shell Bed, Lignite Bed and the Becton-Headon Junction

These is well-seen in Beacon Cliff and particularly just to the west of Taddiford Gap. The double lignite bands provide an excellent marker for the Becton Sands (Barton Sands) - Headon Hill Formation junction.

Under the lignite beds there is shell bed with numerous cerithid gastropods, mostly Batillaria pleurotomoides. See Demassieux (undated) for more information on this species. It occurs in several places in the Tertiary strata of France.

Batillaria of different species are common in intertidal conditions in warm to temperate regions at the present day. Batillaria minima is the Caribbean/West Indian False Cerith. They occur, for example, in Spital Pond, Bermuda where the shells are off-white to black and the bodies black. Batillaria zonalis is the Zoned Cerith or Asian Horn Shell. The subject of Batillaria is easily followed further because there is much information on the internet.

LOCATION - STRATIGRAPHY

Beacon Cliff and Taddiford Gap
- Mammal Bed

The Mammal Bed with rather round, ironstone nodules near its base is well-exposed and accessible in Beacon Cliff. It can also be seen in the basal part of the cliff at Taddiford Gap, and a short distance further east.

Tawney and Keeping (1883)referred to their unit No. 9, as shown in the section above, as the Mammal Bed and listed its thickness as 3.8 metres. In 1883 they commented that they found a Dichobune mandible (this mammal was a swine-like artiodactyl) on their last visit, but that mammals had seldom been found in about the 1870s or 1880s. The Marchioness of Hastings stated that she obtained from the Mammal Bed, or near it, the following:

Anthracotherium
Anoplotherium commune (this is an archaic tylopod - i.e. old distant relative of the camels and lamas - artiodactyls)
Paloplotherium
and also the remains of the turtles - Trionyx and Emys. She found the bones of birds. The Marchioness commented that "the remains are not common and difficult to extract".

As noted on the photograph, the vertebrae of snakes occur under the ironstone. Above it are the vertebrae of lizards, and teeth of mammals and fishes, crocodiles and turtles.

I have only seen one large Palaeotherium limb bone in the Mammal Bed. This early equoid had three toes and some species reached the size of a rhinoceras at about this date. It seems to have been a rather heavy horse-like creature. The group became extinct later and was not on the main line of horse evolution. The Marchioness found an associated set of Palaeotheriod bones in the carbonaceous clay - Bed 10 of Tawney and Keeping (1883).

For up-to-date information see the modern literature on mammals from these strata in the papers of Hooker (1986 and various others). These are referred to in the Barton Bibliography.

LOCATION-STRATIGRAPHY:

Beacon Cliff - Old River Channel

In Beacon Cliff, commencing just to the west of Taddiford Gap, is old Eocene river channel cut into Headon Hill Formation strata. It contains abundant lignitic plant debris.

LOCATION - STRATIGRAPHY:

Beacon Cliff - Pleistocene Gravel

(section to be added)

LOCATION:
TADDIFORD GAP (LONG MEAD END) - General

Taddiford Gap, or Long Mead End, as it is referred to in the older literature, is a small truncated valley reaching the sea at Hordle Cliff. It is probably the best place to make a study of the Headon Hill Formation in the cliff section. The Crodile Bed, the Mammal Bed and other notable features of this part of the Solent Group can be seen just here. By walking eastward from Taddiford Gap the Upper Barton Beds, the Barton Sand or Becton Formation is seen in well-exposed, eroded cliff sections. Walking eastwards will reveal somewhat slumped and overgrown sections of the higher parts of the Headon Hill Formation. The locality is also interesting for the study of coast erosion and the more distant effects of sea-defences.

Drive down the B3058 to the car park (map reference SZ 265925 - Ordnance Survey Outdoor Leisure Map, New Forest 1:25000) near Taddiford Farm between Barton on Sea and Milford on Sea. This a payment car park and there is a short and easy walk (less than half a kilometre) to the cliff top at Taddiford Gap or Long Mead End. Note that there are no toilets here but these are present at Barton and Milford. There are no cafes or shops at hand to obtain food and a visiting party might find it useful to stop at Barton or Milford in advance.

At the cliff top the general geological setting can be discussed (more information to be provided here later). The main danger here is of getting stuck in the mud. Risk from falling debris exists at all cliffs but is not as serious a problem here as at harder rocky cliffs. Watch out for mudslides or mudflows. You are unlikely to sink deep but you can be trapped in cold mud and water for hours. Helicopters and fire-brigade have been involved in rescues on these cliff and, on one occasion, I have pulled a nun out of the mud at Barton.

There is an interesting situation here of a valley, with the Danes Stream, sloping away from the sea so that any coastal retreat will result in a lowering of the cliff here. Only four kilometres to the east the stream flows back to the coast again at Sturt Pond and Hurst Castle Spit (think about the reasons for this). Water flows through the gravels, particularly on the west side of the depression (why?) , and there are special flood protection measures in the valley to the northeast (inland).

Additional note - 2003. As mentioned above in the safety section, there has been erosion of the cliff at Taddiford or Long Mead End and at times it may not be easy to gain access to the beach here. The state of the cliff varies, of course, but increased erosion in the future is likely the make the situation more difficult here and, in addition, the coastal footpath may be cut through. Usually, though, there are other access point at a short walk both east, towards Milford, and west near Becton Bunny.

LOCATION:
Taddiford Gap - Coast Erosion

Comparative photographs from 1998 and 2003 are shown here. In the top, older photograph, if you look west of the Taddiford or Long Mead End valley you can see that the old footpath has been cut through in places and a new footpath has been established further back. The cliffs here are retreating at a progressively greater rate further west towards Becton Bunny. The two "Dragon's Teeth" are relicts of a row of anti-tank defences against invasion by the Germans in the 1940s. In various places the relics of the military defences of the 1940s are quite useful to show the extent of coast erosion. The survival of the dragon's teeth show that erosion from the 1940s to 1998 had been quite limited here to beyond that year (but compare with the gun emplacement at Naish Farm ). By 2003, though, erosion had increased and now we see the collapse of the dragon's teeth and a significant narrowing of the beach. In addition there is exposure of siderite nodules referred to below.

In this image, Environmental Geology students from Southampton University are assessing the variation in the extent of coast erosion along the stretch of cliff immediately east of Becton Bunny (and west of Long Mead End). They are standing on the remains of some concrete foundations (for what?), part of which has disappeared over the cliff. The main feature to see just here is a new embayment formed since sea-defences at Barton-on-Sea, west of here, were constructed some years ago.

The beach material normally comes from the Pleistocene gravels in these cliffs as they evenly retreat. Prevailing south-westerly winds cause the waves on the shore to wash it along the beach from west to east. This coast has changed significantly if comparison is made between old and modern maps or, perhaps, old and modern photographs. Consider whether the natural supply and movement of beach shingle been reduced or stopped by the sea-defences of Barton-on-sea and/or by a projecting sewer pipe and wall near the small valley of Becton Bunny. If the supply of beach material is cut off or diminished the beach is likely to reduce in width and the potential for coast erosion increases. The process of increased erosion at the end of sea-defences in the direction of long-shore drift is known as terminal scour.

The present author has known this stretch of coastline since the 1950s when the coast here was relatively straight. The rate of erosion near Becton Bunny has become much more pronounced in recent years and this is now a good area for seeing clean exposures of the strata with good fossil content. The cutting-back has formed a new embayment between Becton Bunny and Taddiford (Long Mead End).

LOCATION:

Taddiford Gap - Coast Erosion - Loss of Beach Shingle

The photographs here record a new phase of coastal erosion at Taddiford. The base of the shingle beach is knotched with obvious wave erosion and siderite (ironstone) nodules are revealed.

With regard to the history of this site, the best vertebrate finds at Hordle Cliff seem to have been made in the 19th century and include a crocodile skull. It thus seems likely that the cliff was undergoing appreciable erosion at that time. Much later, in the 1950s the present author was familiar with the beach at Taddiford and it was of moderate width. The erosion of the cliffs was limited here but it was still possible to find some crocodile bones in the crocodile bed. After this phase and later in the 20th century there was an expansion of the width of the beach at Taddiford and the crest of the berm was some way out from the foot of the cliffs. There was clearly some realignment of the beach which may or may not have resulted from the construction of sea-defences. Towards the end of the 20th century the erosion was very marked at Becton Bunny, as mentioned, but it did not affect Taddiford. The new development now, and one that has taken place since 1998, but has only recently been seen by the author, is this exposure of siderite (ironstone) nodules as a result of erosion of the foot of the beach. Destructive-type waves were in progress at the time of photography and the relative lack of storm conditions in the dry summer of 2003 might have increased this type of erosion. Nevertheless it is a clear sign of increased erosion here, and this seems to be confirmed by the retreat of the cliff top and a relatively narrow beach at present. It is probable that this is extension eastward of the area of major cliff erosion that is east of Becton Bunny. This is presumably the result of progessive loss of beach material. No investigation has been made by the writer (although others might be studying it). The long-term implications are not known but this clearly something to watch. The general situation in October 2003 is that the cliffs to the east of Taddiford Gap or Long Mead End are not showing much erosion (other than within a 100m of the gap). They are quite vegetated, unlike the cliffs to the west. We will see what effect the forthcoming winter storms have on this stretch of coast.

The nodules are ex situ and probably represent the boulder base of the beach. There are three main ironstone horizons in the cliff and no study has yet been made to determine which was the source bed. Of course, more than one horizon may have contributed material which fell from the cliffs. The most likely source, though, is probably the well-developed Mammal Bed ironstone.

At the low spring tide on 10 March 2005 more siderite (ironstone) nodules were found ex situ in a narrow lagoon low on the beach. This is also just east of Taddiford Gap and these represent accumulation from some former position of the cliff here, perhaps about 100 years or more ago. A short distance further east there are remains of scaffolding from military defences of the second world war. This again indicates that there here, a hundred metres or so east of Taddiford Gap, there has been very little retreat of the beach and cliffs since the 1940s. This accords with the evidence from the vegetated state of the cliff.

Incidently the accessibility of ironstone here at different times in the past might have some relevance to historical or archaeological investigations regarding local use of siderite (as at Sowley Pond). Ironstone is now less visible that is usually the case at Hengistbury Head, but this Hordle Cliff ironstone is becoming increasing visible. A difference between the two is that the Hengistbury ironstone contains glauconite and rare marine fossils. The ironstone here is more likely to contain freshwater fossils. I doubt if it contains glauconite but I have not investigated this matter.

LOCATION - STRATIGRAPHY:

Taddiford Gap

- The Crocodile Bed

The Crocodile Bed,15b, is an easily-recognised, very fine sand, weathering whitish. It originally received the name "Crocodile bed" by Wright in 1851. Most of the bones were found in the 1840s including a fine skull. I was still able to find crocodile vertebrae like those above just east of Taddiford Gap in the 1950s, although they were rather delicate and needed excavating with care and then hardening with a resin. Edwards and Daley (1997) commented that extensive excavations in the outcrop midway between Hordle House School and Taddiford Gap ( Hastings, 1853) yielded abundant scales of the ganoid fish Lepisosteus fimbriatus (Wood) and much less common skulls, dermal scutes and post-cranial bones of a crocodilian. Also present were trionychid (i.e. like Trionyx) turtle carapaces and mammalian remains. The fossils occurred in greenish mud lenses, at approximately 0.60m below the top ( Tawney and Keeping, 1883). A revised list of mammals from this horizon has been given by Hooker (1987). Teeth and waterworn bones were also found in bed 13, the "Rolled bone bed" of Tawney and Keeping (1883).

Here is an example of some common fossils from just beneath the Crocodile Bed, probably from bed 15a. Potamomya plana (J. Sowerby) is a low salinity, thin-shelled bivalve that commonly occurs with the pond-snail Viviparus in the Headon Hill Formation. Scattered amongst the shells are small black seeds, Brasenia ovula Brongniart, according to Edwards and Daley (1977). The small bivalve Potamomya plana ( which used to be known as Erodona plana) is common. There are some fish remains in this bed, particularly small fish vertebrae, now dark brown in colour. Brown fragments of turtle carapace are fairly common in the Headon Hill Formation. The Hampshire Crocodile, Diplocynodon hantoniensis is rare but of particular interest.

More details on the Crocodile Bed are given in these extracts from Tawney and Keeping (1883) give their own observations and also refer to the fossil records of Barbara, Marchioness of Hastings. She lived at Efford, near Lymington, and her doctor owned Hordle Cliff.

"The description of the these deposits by the late Marchioness of Hastings contains the best information concerning the exact beds in which the vertebrate remains were found. We have collated the beds in the Marchioness's description with our own, and quote largely from her work, as it has never been translated into English. It is indeed fortunate that she has so carefully preserved the information for us relating to the beds which yielded the vertebrate remains.

The senior of the writers [presumably E.B. Tawney, Esq., M.A.] was then acting as her collector. He lived for a great part of his life close to Hordwell Cliff, and for four or five years worked regularly on the cliffs, collecting fossils for the Marchioness. Facts relating to the exact spots where the vertebrate and other remains were found were communicated to her, though occasionally she would assist with her presence. We are making this particular admission, because there are some statements in her description which the writer cannot reconcile with his memory or with the present state of the cliff... "

[Crododile Bed] "(15) At the top is soft sand with Paludina lenta [Viviparus lentus ], Limnaea caudata [Galba ], Cyrena arenaria [Corbicula?], Dreissena, Lepidosteus [fish] and Crocodile; then hard sand of pale or whitish tint with plates of Turtles, and bands of Potamomya plana; below are whity-brown sands, with carbonaceous layers and Potamomya in bands. The whole about 7 feet thick [2.1 m], may be called the Crocodile-bed, having been so known to local collectors; the best horizon for Crocodiles is about 5 feet (1.5m) up in this bed.

In the Marchioness's section it is No. 10, .. and seeds of Chara are mentioned. She also says that ... Potamides [a turreted gastropod] is found. In the Woodwardian Museum there is a Crocodilus Hastingsiae collected by one of us, with several specimens of Potamides pyrgota in the matrix among the bones. The Marchioness draws attention to this association. Of mammals, she mentions Paloplotherium, Dichobune, Hyaenodon, found in this bed [see modern works of Hooker on Eocene/Oligocene mammals of southern England]; of reptiles, besides the Crocodile, are [the turtles]Trionyx Henrici, T. Barbarae, T. marginatus, T. circumsulcatus and Emys crassus. Dr Wright states that Palaeotherium splenum, P. parvum, P. annectens, Microchaerus, and Spalacodon were also found in this bed. He does not state his authority. Searles Wood, in figuring Microchaerus does not state in which bed he found it."

[Beneath the Crocodile Bed] "(14) Greenish clay, 2 inches [ 5 cm] ; whity-brown sand, 6 inches [15 cm]; bluish grey clay-band, 1 inch [2.5 cm], with Melanopsis brevis.

[Rolled Bone Bed] (13) Light greyish-white sands 6 - 9 inches [15 - 23 cm]: a constant bed. It may be called the Rolled-bone bed, from the abraded state of the remains. Mammalian bones, Emys, Trionyx [turtles] and Crocodile are mentioned by the Marchioness. "

Owen (1861), after mentioning a gavial-like crocodile, from Bracklesham Bay commented: "In the Hordle beds have been found the C. Hastingsiae, with short and broad jaws; and also a true alligator (C. Hantoniensis). It is remarkable that forms of procoelian Crocodilia, now geographically restricted - the gavial to Asia, the alligator to America, and the true crocodiles to warm latitudes of Asia, Africa and America - should have been associated together, and represented by species which lived, during nearly the same geological period [Eocene], in rivers flowing over what now forms the south coast of England.

For an illustration of Diplocynodon, the genus in which the Hordle Cliff crocodile - Diplocynodon hantoniensis is now placed, see an example from London Clay of the Isle of Sheppey. The opening page of this excellent website, relevant in many respects to the Barton and Hordle webpages, is at Sheppey Fossils, Lower Eocene (Ypresian) fossils of the London Clay from the north coastal section of the Isle of Sheppey, Kent, UK. There is also a complete specimen of Diplocynodon figured from the Museum Victoria , Australia.

LOCATION-STRATIGRAPHY:

Taddiford Gap continued

- Crocodile Bed - the Hampshire Alligator

Diplocynodon of Hordle Cliff was a type of alligator, rather than a typical crocodile, and it had an unusually long snout and peculiar teeth. In the upper jaw were two pairs of caniniform (canine-like) teeth, instead of one, according to Steel (1989) . They were in the fourth and fifth position. In the lower jaw there were three pairs of extra-large teeth (the first, third and fourth). Other genera of European alligators have the conventional upper-jaw sockets for the lower jaw teeth (unlike true crocodiles). Steel (1989) pointed out that Diplocynodon hantoniensis initially caused some confusion because the skulls have upper jaw knotches rather than complete sockets. This is why it became named as Crocodylus hastingsiae (the Marchioness of Hasting's crocodile, sometimes known as the Hampshire Crocodile). It was more correctly the "Hampshire Alligator" and lived amongst a type of Florida swamp-cypress tree (Taxodium ) which is also found at Hordle Cliff. The New Forest region was a Florida-type lagoon and cypress-swamp, warm enough for the alligators and with plenty of mammalian prey such as the horse-like Palaeotherium, bones of which can also be found in this cliff.

To consider the history, as given by Steel (1989) , Diplocynodon hantoniensis belongs to a genus that has been widespread in the Cenozoic from about 50 million years ago and lasted until only a few million years ago. This alligator lived in North America in the Middle Eocene but has not been found there is later strata. It may have originated in North America, an ancestral-type form Prodiplocynodon was living in Wyoming in the Late Cretaceous, before the extinction of the dinosaurs. It was a surviving reptile. In Europe Diplocynodon ranged from the Middle Eocene to the Middle Pliocene and occurs from Spain through southern England to Bulgaria. At Hordle Cliff (Upper Eocene) there is evidence of these alligators on the sandbanks near the margin of the lagoon. It is probable that Diplocynodon was the common British alligator for millions of years, but disappeared with cooling at the early signs of approach of the Pleistocene ice-age.

Not only are alligators much more restricted in distribution now, but so too are certain coniferous trees. Sequoia trees were the most abundant tree of Dartmoor in Oligocene times, yet the early sequoia ancestors seems to have evolved in the late Cretaceous in north-eastern Russia. Sequoia now lives naturally in the western USA and is not a native plant of Britain, but when planted in the New Forest (e.g. at Rhinefield) can grow large. Taxodium , the swamp-cypress is, noted above, a tree of Florida, but the fossil trunks of its relatives are in Hordle Cliff. The swamp-cypress, too, will also grow in Britain when planted in a favourable environment (e.g. the lake in Kew Gardens).

LOCATION - STRATIGRAPHY:

Taddiford Gap continued
- The Limnean Limestone

The Limnean Limestone is a thin limestone that was deposited in a freshwater lake. The main gastropod is Galba longiscata which was originally referred to here as "Limnea" or "Lymnea ". When the cliffs are not undergoing active erosion the bed may not be easily found. Renewned erosion just to the east of Taddiford Gap in 2007 has clearly revealed it.

Galba is a eurytopic [i.e. able to adapt to a wide range of environmental conditions; widely distributed], pulmonate [i.e. air-breathing], gastropod, that lives on water-weed in freshwater lakes. At the present day there is, for example, a lake in Turkey, Lake Sapanca in Marmara (Kosal Sahin and Yildrihim, 2007) , that has abundant Galba truncatula (formerly known as Lymnaea truncatula) and at about 40 degree North is about the correct latitude for Hordle Cliff in the late Eocene [now 51 degrees north because the equator has moved south since then]. This lake has water plants including Chara, which accords with the charophyte oogonia remains in the Limnean Limestone. It also has the common flat-coiled gastropod, Planorbis planorbis which can be compared to the Planorbina euomphalus of the the Limnean Limestone at Hordle Cliff. Of course Lake Sapanca is not a unique environment for comparison to the Hampshire Eocene lake. There are many other warm temperate lakes today that are similar. Lake Sapanca is rather high at about 30 metres above sea-level. The Hordle Cliff Lake was close to sea-level and very shallow.

LOCATION:

Hordle Cliff, sensu stricto, and Hordle Village

The main stretch of Hordle Cliff, sensu stricto extends for about one and half kilometres to the east of Taddiford Gap. The cliff takes its name from the former village of Hordle or Hordwell, which with its church, was in the situated on the cliff top. It is shown on Norden's map of 1595 and Cary's map of 1787. The village was destroyed by coast erosion in the early part of the 19th century. This was an actively eroding area and good for fossil collecting at the time of Marchioness of Hastings and the early geological work on the Headon Beds. This part is now inactive and largely vegetated. Erosion, however, is just commencing again (in 2007) at the western, Taddiford end.

This Cliff is in perpendicular height about fify yards from the sea, at high water mark and extends about a mile and a half along shore; it is composed chiefly of red gravel, to about 18 or 20 yards below the surface [anomalously thick], but amongst the gravel very few shells or remains of marine bodies are to be found.

In many parts of the Cliff there are large veins, or rather masses, of a mouldering soft blue clay, through land springs are continually trickling down, which by degrees loosens the clay and causes it to slide away in great beds, one below another, and the frost may not a little contribute to this effect. So that the surface has in a few years been greatly worn away.

When the fall of this Cliff happens there then found perhaps the greatest variety both of the turbinated and bivalve shells that were ever met with in any one place in the world, in their original state, and have suffered no change for innumerable ages past, this so remarkable a circumstance may be dayly verified by inspecting the cabinets of the curious.

Many of the shells are the natural inhabitants of very distant regions, and some of them entirely unknown, either in their natural or fossil state.

towards the bottom of this Cliff there are frequently found large nodules of a hard reddish ironstone or marble [this is the Shell Bed or Stone Band (G) at the top of the Barton Clay], being no other than an entire mass of shells, with which the church [presumably the church at the original cliff top village of Hordle, now destroyed by the sea] and other edifices are built.

LOCATION - STRATIGRAPHY:

Paddy's Gap Area, Milford-on-Sea
- Unio Bed (No. 31)

Between the Hordle Cliff car park at Milford-on-Sea and the Paddy's Gap car park there are small but interesting cliff exposures of the Unio Bed (No. 30) and associated strata. The shining, "mother-of-pearl" shells of the freshwater mussel "Unio" are common here, but often broken. They are not the most abundant fossils. Gastropods, particularlyViviparus lentus (Solander), are conspicuous in almost every unit here. The very small gastropod Potamaclis turritissima (Forbes) is easily recognised by its descriptive name, but almost needs a handlens to see it well. At the base of the fossiliferous beds in the cliff is a thin band with numerous seeds of the Water Soldier or Water Aloe. These were known in Victorian times as Carpolithes but are now placed in the genus Stratiotes.

PLEISTOCENE - LOCATION:

Pleistocene Sarsen Stone near Paddy's Gap

Paddy's Gap to the White House
- Coast Erosion and Storm Activity

The short stretch of coast from Paddy's Gap to the White House is very interesting. It is the part of Christchurch Bay which is most depleted in terms of beach material. This was not the case in the past, and thus its cause is an interesting problem. The relatively low cliff is protected by a sea wall with gravel at the back and, now, rock armour (largely Carboniferous Limestone) in front. Presumably this has been required because of the risk of rapid coastal reatreat which might take place. Apart from the White House, there is no housing immediately on the cliff top, but it is not far back from the cliffs.

Thus, this is an interesting place to observe problems of the horizontal proximity of the sea to the location of the cliff top. There is a very narrow cliff and no beach at high tide. The sea wall is not very high but is regularly maintained. Gaps could be filled with rock armour and gravel, should they appear. However, the longer term prospects are interesting to consider. Rising sea level and more storms are very likely to cause problems here over the next 100 years. Quite apart from a probable rise in sea-level or 60 cm or a metre over a hundred years, major storm events may take place. In any case, the great 1824-type hurricane has not yet returned. When this one-in-250 year event happens again, as, of course, it will then the sea attack here could be very serious, much more so than shown in the photographs below.

This storm in the morning of a day in January, 1998 hit the Hordle coastline quite severely (anyone interested could probably find meteorological records regarding the storm). The photographs shown here were taken at Rook Cliff, Milford on Sea, east of the main Hordle Cliff geological section. ,where there are some sea-defences. The location of photography was from the eastern side of a car-park (map reference SZ 282917) on the greensward at the western end of Milford. In the distance is the old sea-front hospital, with a characteristic horseshoe-shaped plan. There is a promenade and sea-wall at the foot of the cliff here and groynes commence at this location and are placed at intervals between here and the building in the distance, as can be seen in the photographs. They seem to be little consequence in these conditions. The storm waves are oblique to the coast and are coming from a southwesterly direction, that of maximum fetch. These can come up the English Channel, just missing the Brittany Peninsula, to the south, and just missing the Isle of Purbeck peninsula, not far away. The southwesterly direction is that of the prevailing wind and storms from this direction are common occurrences when Atlantic depressions and fronts hit the region in the winter. Thus big waves, perhaps originating from the Atlantic, can occasionally attack the coast from Barton-on-Sea eastward to Hordle Cliff, Milford-on-Sea and Hurst Castle Spit (and the western Isle of Wight). Highcliffe, further west is, of course, not completely safe from major wave attack but is protected to some extent not only by the Isle of Purbeck, but also by the promontory of Hengistbury Head. Relatively shallow water can reduce the wave effect to some extent. Nevertheless this is an interesting stretch of coast in geomorphological terms, because it has the combination of cliffs of poorly consolidated clay, sand and gravel and the occasional subjection to major storm waves from the southwest.

We can now consider the details of the particular storm event. The waves were impacting on the sea-wall of the promenade and throwing water and spray high so that it could reach to top of the cliffs, only at about 10m here. Sea-water then ran back seaward down the cliffs eroding Pleistocene gravel and carrying down to the promenade and the sea. This brown gravel is the cause of discolouration of the sea-water. The gravel was churned up in the waves and then thrown back again up the cliff. Gravel thus landed on the cliff top and in one of the photographs an individual pebble in movement in the air can be seen. The showering of gravel on the cliff-top made the author aware that he had parked his car in an unsatisfactory place (quite apart from the sever wind-buffeting and the salt-water wash) and although impact damage to the windscreen was only minor the visit was necessarily curtailed. In the afternoon the wind-speed decreased to more normal conditions.

Milford-on-Sea is at the eastern end of Christchurch Bay. The prevailing winds are from the southwest and thus the dominant long-shore drift is towards the east. In natural conditions, without the presence of major sea-defences hindering supply and movement, shingle from the Pleistocene gravels of Barton-on-Sea and Hordle Cliff is transported eastward along the beach to Milford-on-Sea and thence to Hurst Castle Spit (where, indeed, some Barton fossils are found). The normal consequence of this is a build-up of beach material at Milford and this has, in the past, probably retarded cliff retreat. The offshore bar, which would also have consisted of material drifted from the west, would also have provided some protection by moderating the effect of waves. The photograph above shows a small part of the beach in its natural condition in 1932. At this time the beach was wide and the berm rose to almost the level of the land surface at this location. The crest shows oblique ridges because of some alignment to a mild promontory at Rook Cliff and Hordle Cliff to the west of this. Thus in natural circumstances Milford is to some extent a location of accretion whereas Barton is primarily a location of erosion and supply of pebbles. Conditions have changed now but Milford-on-Sea has probably been subject to a low rate of coast erosion in the past because of the broad protective beach and the offshore bar. The natural sea-defences have largely been lost now but the concrete and blocks of Carboniferous Limestone, the main artificial substitutes, seem to be holding firmly, at least for the present. The landward beach limit or effective cliff-line has retreated a little beyond the trend of the wall, especially on the east side (the down-drift side) of the concrete defences shown.

COAST EROSION AT MILFORD-ON-SEA continued:

The White House at Milford-on-Sea

At Milford-on-Sea, the most impressive feature of the sea-front is the White House. This was built in 1902 by the Walker-Munro family, colliery millionaires of Rhinefield House in the New Forest. This summer sea-side residence became a children's hospital from 1938 to 1983, and in 1999 was restored by Colten Developments Ltd. It is a nice building of historic interest. It is also of geomorphological significance as marker with regard to coastline recession and longshore drift of gravel, and is referred to again below (see 1938 ). It originally had a broad beach in front of it, but it is now protected by a small promontory of sea defences.

Coast retreat is clearly seen at the White House from the above photograph. One is from 1932 and the other one from 2003.

The seafront at Milford-on-Sea is important to Hurst Spit because it is the feeder area, through which in the past the shingle from the Barton and Hordle cliffs reached the spit. A aerial photograph of the White House, the conspicous white building to the west of the small town (and mentioned above), was taken in 1932. It shows the two lookout or viewpoint buildings aligned with the back of the beach. As mentioned above, it was built in 1902. Its exact relationship to the beach at that time is not known, but since coast erosion here has been progressive it is probable that the beach was even wider or further to south in 1902 than in 1932 . Notice, incidently, that in 1838 the narrow concrete wall, oblique to the coast, was already in existence already. Perhaps, there had already been some threat of coast erosion. I wonder why it is not parallel to the sea frontage of the building; perhaps it was intended to trap the southeast-moving gravel.

In 1938, unlike the present day, there was a wide beach that seems not to have been significantly damaged or destroyed by sea defences to the west. Shingle could then pass by long-shore drift from west to east (in accordance with prevailing southwesterly winds) and supply Hurst Spit.

The photograph of the White House on the 6 May 2001 by the Channel Coastal Observatory, shows a very different situation. Much rock armour has been placed in front, and there is more of this further west. Now shingle cannot easily pass the various obstructions, of which this is only one. In any case it cannot proceed further southeast because of major sea defences at the Milford end of Hurst Spit.

COAST EROSION AT MILFORT-ON-SEA continued:

Milford-on-Sea - the Main Sea Front

The short stretch of low coast at Milford-on-Sea contrasts with the cliffed coast of most of Christchurch Bay. In historic times this area has receded more or less in line with the adjacent Hurst Spit. Now, however, Hurst Beach is a little further back but is protected at this end by a high embankment of larvikite rock armour. This part should resist even very severe hurricanes. The sea front area at Milford has much lower concrete sea walls, although they defend against normal storms. The land behind is m mostly above the possible flood level of the Environment Agency Flood Maps. In fact, it does not seem to suffered much recently, apart from some minor washover at the southeastern end. Whether the lower sea defences here, though, will protect against washover from a severe hurricane with storm surge, like the 1824 event, is not known. Whether there will be any longterm future problem here with global warming and rising sea level is not known either (if necessary, perhaps it might be possible to continue the larvikite rock armour bank westward across the car park, so that a strong and high sea wall would exist from the White House area, Milford, southeast to the southeastern end of the larvikite on Hurst Spit.)

COAST EROSION AT MILFORD-ON-SEA: Milford-on-Sea
Sea Encroachment in 1953

Newspaper report: Anonymous (1953). Sea encroaches 30-40 feet. New Milton Advertiser, 25 July 1953, p.1. Article not seen, but referred to by Delair (2007).

COAST EROSION AT MILFORD-ON-SEA continued:

Hurst Spit and its Relationship to Milford-on-Sea

Hurst Castle Spit is discussed in detail in a separate but associated webpage - Hurst Spit. It is, however, relevant to mention it here in relation to movement of beach material from and past Hordle Cliff and in relation to Milford-on-Sea. The spit represents the destination of subangular flint gravel travelling by long-shore drift eastward from the supply cliffs of Highcliffe, Barton-on-Sea and Hordle Cliff. The supply from Highcliffe and Barton has been cut by sea-defences long ago but the beach at Hordle Cliff has remained quite wide, at least until recently. There has been much residual gravel and the increased erosion at Beacon Cliff must have helped. In addition there has been some realignment of the trend of the beach (probably a very small clockwise shift in the Hordle Cliff area) which has had its effect.

The natural overall retreat of the coast must have caused some concern at Milford-on-Sea back in the 1950s because at about that time some defences were constructed there (as indicated by old photographs). The sea-defences have been strengthened there (see the images above regarding Milford) and now it is very difficult for shingle to pass eastward of Milford beach. The Hordle Cliff, Barton and Highcliffe shingle is not able to reach the spit. At the landward end of this geomorphological feature some sea-defences in the form of rock armour were added. This seems to protected part of the beach but reduced shingle supply eastward. Thus, in February 1979, the sea almost breached the beach directly east of the sea-defences and the beach ridge was stepped back out of line. Later, after after a major flattening of the shingle spit by the sea, Hurst Spit was rebuilt from larvikite and dredged shingle. For more information on Hurst Spit and on its artificial reconstruction see: the Hurst Spit webpage.

END OF FIELD GUIDE - Or on to Adjacent Coasts?

ACKNOWLEDGEMENTS

I am grateful to the various students and members of my family who have worked with me on field trips or projects in this area. I am particularly grateful to the Director and staff of the The Channel Coastal Observatory for permission to use their excellent, vertical, aerial photographs.