West, Ian. M. 2016. [correct version to use, but this needs updating] Studland and the South Haven Peninsula - Poole Harbour Side; Geology of the Wessex Coast of southern England. Internet site: www.southampton.ac.uk/~imw/Studland-Poole-Harbour-Side.htm.
Studland and South Haven Peninsula - Poole Harbour Side,  Field Guide

Ian West, Romsey, Hampshire
and Visiting Scientist at:
Faculty of Natural and Environmental Sciences,
Southampton University,

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Other Webpages on Studland and Adjacent Area:

|Studland - South Haven Peninsula (the main page on Studland) |Studland Peninsula - Poole Harbour Side (this webpage) |Brownsea Island Geology |Studland - Tertiary Cliffs |Harry Rocks, Ballard Point |Swanage Bay |Studland and Harry Rocks; Bibliography |Swanage Bay |Sandbanks Peninsula

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This is a branch page of the main Studland page at:
Studland - South Haven Peninsula (main page)

Eocene sandstone in low cliffs at Redhorn Quay, Studland, Dorset, as pointed out by Ian West


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Safety and Risk Assessment

Risks are not particularly great here, but there may be some. There is some chance on the harbour side of the Studland Peninsula of becoming stuck in mud in the harbour. Avoid wandering out away from the shore onto the mudflats. Stay very close to the heath and watch out for any patches of soft mud. Visitors should have clothing suitable for the weather and aA mobile phone for use in emergencies. In warm weather there may be occasional adders in the heathland. Note that in the Second World War the South Haven Peninsula was used for military training. The area has been cleared of missiles and mines etc, but take care. Persons may need to make their own risk assessments and take note of the conditions on the day. No liability is accepted. This is a nature reserve, so do not disturb bird life and avoid the remote shore areas where possible. Persons undertaking field work here should do so in accordance with the rules of the National Trust who own the area.

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1.4 INTRODUCTION: Geological Maps

It is important to note that for an area such as Studland there have nomenclatural changes from the old series of BGS geological maps to new Bournemouth and the new Swanage maps. Re regard to the Chalk note that the Portsdown Chalk Formation is in the zone of Belemnitella mucronata. The older literature uses the zonal name, as the Formation name is relalively new. This should not cause much problem at Studland, and in webpages dealing largely with the Chalk, a conversion table is provided.

The Palaeogene or Tertiary strata are not quite so easy to deal with. The greatest change has been the replacement of the old "Bagshot Beds" with the name Poole Formation and an important subdivision of this into members. New maps in this webpage, use of course, the new scheme, but some parts of older maps are also reproduced (and may sometimes be more readily available because of copyright matters). There should be no problem in using an old matter in introductory terms, if the reader has some familiarity with both old and new nomenclatures. The experienced geologist will know whether an old or new scheme is being used.

[This website will be progressively updated to use the new scheme, but old terminology may persist in parts until time permits correction.]

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A simplified geological map of the South Haven Peninsula and Studland, Dorset, based on modern geological maps, but completely redrawn, 2014

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This simplified geological map above has been completely redrawn, with appreciable modifications. It is based partly on the data shown in the Bournemouth Sheet (No. 329) of 1991, and partly on the data shown in the Swanage Sheet (No. 342 east and 343) but does not show the Ordnance Survey data which is present on those maps. All boundaries have been shown with solid lines, unlike the BGS map, so distinction is not made between proven and postulated geological boundaries. The map is very simple in structural terms with some faults in the southernmost part and some minor synclines and a corresponding anticline. Away from the southern boundary area (i.e. at and near the Chalk) the structure is simple with overall a very low dip towards the north. Note that the map shows not just formations but also members. Some of these are very thin, just a few metres and they are variable in thickness. This particularly applies to the Poole Formation. This Eocene unit is a product of sedimentation in the hot Poole Delta. Channels within this delta were irregular and moved in position from time to time. There were lakes, and probably crevasse-splays in places. Abandoned channels in the local Eocene sediments were often filled with plant-rich clay plugs. Inevitably in such an environment, extremely reducing conditions were locally developed. Pyrite was worked economically in the past from the Poole Formation on Brownsea Island. There has been extensive oxidation of pyrite in the Parkstone Clay Member. This has resulted in brown, ferruginous cementation of the Parkstone Sand Member. The most obvious and well-known example of this is the Agglestone Rock and the nearby Puckstone. Similarly the Broadstone Sand Member shows iron-cementation at Redend Point. Here, too, there are pyritic pipes, now oxidised (above sea-level) to limonite, and coloured sands, with the colouring the result of the state and type of iron oxidation.

A special feature of the area, and shown on the map above, is the absence of the Reading Formation, with London Clay (very sandy) faulted against Portsdown Chalk.

The sand dunes and sand beach deposits of the South Haven Peninsula are discussed in the webpage: Studland - South Haven Peninsula etc.

Incidently, note that the BGS maps show "Head" associated with and mainly to the west of the dune ridges. Most Head is of Pleistocene origin, but there is a question about these particular deposits because of their close association with Holocene sand.

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Older and newer interpretations of the geology of the Studland or South Haven Peninsula, Dorset

See the latest edition of the Swanage Sheet, 343 and part of 329 of the British Geological Survey . Not only have some details of the map interpretation changed but as will be discussed below, the Studland peninsula itself has changed!)

The North Haven Peninsula, Sandbanks, and the South Haven Peninsula, Studland as shown on part of Ralph Treswell's map of the Isle of Purbeck,  1585-6

A personal  interpretation of part of the map by Ralph Treswell in 1585-6 of the South Haven Peninsula, Studland, Dorset

This map by Ralph Treswall in 1585-6 (also with a personal interpretation) shows the South Haven Peninula before development of the main area of blown sand. The small promontories of Redhorn Quay, Jerry's Point and Gravel Point are present. From there northwards a shingle spit extended towards the the North Haven Peninsula or Sandbanks.

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5.5 STUDLAND PENINSULA - POOLE HARBOUR SIDE - LOCATIONS:

Gravel Point

Gravel Point

Subangular gravel at Gravel Point

Cardium and pebbles

Near South Haven Point on the Poole Harbour side is a very small promontory known as Gravel Point (map reference SY 033864). It is about the northernmost limit of gravel, as opposed to sand on the beaches of the Poole Harbour side of the South Haven Peninsula. No gravel occurs on the seaward side much to the north of Redend Point. As noted above, the area is primarily one of sea washed and blown sand accumulation and very little pebble transport occurs here, now. In the early 17th Century, though, as shown on the historic maps there was merely a narrow strip of land extending northward from the village of Studland on the position of the present harbour (northwestern) side of the peninsula. This seems to have been a rather irregular continuation of the beach at Redend Point towards Sandbanks. The old narrow peninsula, present before the build-up of sand dunes, seems to have ended at about Gravel Point. This was probably the original stony limit of the peninsula.

A photograph above shows Gravel Point, with some oystercatchers (Haematopus ostralegus a common autumn and winter shore bird of British estuaries and which feeds on molluscs, crustacea, worms and insects, including the cockle Cardium, not oysters). Beyond the gravel at Gravel Point, looking north you can see some of the blown sand.

Another photograph shows subangular flint gravel, undergoing some minor erosion from the cliffs. This gravel is not Pleistocene flint gravel in place but reworked gravel, probably much from the Pleistocene, but possibly including material transported some distance along a former shoreline by longshore drift. Notice that there are whitened pebbles which have been in the upper part of an acid podsol soil profile and brown pebbles that come from Pleistocene gravel without much leaching. Note that there is also a mixture of pebble types in the low cliff at the back of this small area of beach.

The third photograph shows a typical piece of beach near here where there is sand, subangular flint pebbles and a broken Cardium or Cerastoderma (i.e. cockle) shell. This is a good representation of the type of mixed sediment that can occur on the harbour shores in this area. Notice how poorly sorted is the sand. This is because of supply of coarse grains from the gravel (not available in the blown sand). Notice also the green algal slime on some pebbles. This is typical of the harbour environments and would not normally occur on the open sea beaches where abrasion would destroy such coatings. To the left of the shell is some debris of mucus-cemented worm tubes. The small rounded pebble is of vein quartz and has a long history. It has undoubtedly been reworked through Pleistocene gravel and iron stained but it is probably ultimately of Palaeozoic origin.

The details of the very low cliffs at Gravel Point are interesting and warrant further study. There are some old marsh deposits with a gley soil profile. In these the brown limonitic patches have turned red in the transition to hematite.

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Jerry's Point, Brand's Bay, Poole Harbour

Shelducks on the east side of the South Haven, Studland, peninsula, above the horizontal wells and only one and half kilometres east of the main drilling site of the Wytch Farm Oilfield, 5th June 2014

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Jerry's Point is a small recurved spit. It is only one and a half kilometres east of the main drilling site, M, of the Wytch Farm Oilfield. That drill site is on the Goathorn Peninsula on the other side of Brand's Bay. It is best not to disturb the birds here.

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Between Jerry's Point and Redhorn Quay, Brand's Bay, Poole Harbour

[Ready for additions]

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Redhorn Quay, Brand's Bay, Poole Harbour

Approaching Redhorn Quay, Studland, Dorset, from the heath, showing sand, Spartina and a rusting boat, 5th June 2014

Out at Redhorn Quay, on Poole Harbour, near Studland, Dorset, 5th June 2014

Looking landward, eastward, at the end of Redhorn Quay, Studland, Dorset, 5th June 2014

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No drilling derrick, but just a crane at the Wytch Farm site M, on the Goathorn Peninsula, as seen from Redhorn Quay, Studland, 5th June 2014

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Redhorn Quay is an old abandoned quay, shown on a map of 1586, that was once important for transport from the Studland area to Brownsea Island, Poole and elsewhere. It is very close to the relatively deep channel of Redhorn Lake. There were some rotting hulks of boats (almost all gone now) and the broken and eroded remains of the old quay. Large rectangular blocks of limestone, probably oolitic Portland Stone, are present on the shore and presumably at one time these were part of a quay wall. It is interesting that chalk has been imported to here and dumped at the promontory long ago.

A block of Carboniferous Limestone with corals, associated with Old Red Sandstone debris at Redhorn Quay, Poole Harbour, Studland, Dorset

Above it is sandy debris containing clasts of Old Red Sandstone (Devonian), with quartz veins, and some fossiliferous Carboniferous Limestone, shown above. With it is some weathered Palaeozoic-type slate. This dumped material could have come from South Wales, of possibly further afield such as Scotland. Suitable sources may be present in the Milford Haven area, but the debris has not been studied in detail. I do not know why it is there. Perhaps it has arrived as ballast on a boat. Much of the Old Red Sandstone and slate has been eroded out onto the beach at Redhorn Point. It is hoped that further study may be made by the Poole Harbour Historical Trust.

Low cliffs of iron-cemented sandstone of the Poole Formation, Redhorn Point, Poole Harbour, Studland, Dorset

Cross-bedded sandstone southeast of Redhorn Quay, Poole Harbour, Studland, Dorset

An old Holocene gley soil over cross-bedded sandstone of the Poole Formation at Redhorn Quay, Poole Harbour, Studland, Dorset

The low cliffs at Redhorn Quay provide excellent exposures of sandstone of the Poole Formation. There is some similarity to the Redend Sandstone at Redend Point, Studland. The sandstone is iron-cemented and in places shows the pinkish colours of the coloured sands of Redend Point (and Alum Bay). The grain size is medium sand and it was seen to be as coarse as the Agglestone Grit of the Agglestone Rock. Unlike the Redend Sandstone at Redend Point it does not show a large number of iron pipes. One circular structure which might be a pipe was observed, though. The sandstone is almost horizontal with conspicuous, fairly small-scale, cross bedding. It shows no evidence of marine origin and is presumably fluviatile like the Redend Sandstone and the Agglestone Grit.

Redend Point is a consequence of the more resistant sandstone lying within clays and unconsolidated sands and forming a small headland and ridge.

Small headland with sandstone northeast of Redhorn Quay, Poole Harbour, Studland, Dorset

A short distance to the northeast of Redhorn Quay there is another exposure of ferruginous sandstone, similar to that at Redhorn.

A very large accumulation of algal slime in Brand's Bay, south of Redhorn Quay, Poole Harbour, Studland, Dorset, 2007

In Brand's Bay further to the south there is at present (June 2007) a very large accumulation of algal slime or filamentous green algae. Is the fairly long period of warm sunny weather and the early Spring (global warming?) responsible? Is it instead some consequence of pollution of harbour water by agricultural fertiliser or is it completely normal. I have not looked here on previous years and thus I do not know whether it is a usual feature. With it, on the shore, are numerous small shells of Hydrobia, the common harbour and lagoon gastropod, which probably browses on the algae. Similar algae and gastropods can be seen at the edges of the Keyhaven Marshes at Hurst Spit, Hampshire.

A little further south is a bird observatory.

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5.10 STUDLAND LOCATIONS:

Unexplained Circles between Jerry's Point and Redhorn Quay

Unexplained circles on the heath, near Jerry's Point Studland, Dorset

A circular depression on the heath near Jerry's Point and Redhorn Quay, Studland, Dorset

There are some strange circular features on the heath northwest of the road to the ferry which are unexplained. They are shallow depressions with narrow and low raised rims. They seem to be old because a well-defined footpath passes through one of them as can be seen in the aerial photograph above (courtesy of the Channel Coastal Observatory).

Before the development of the South Haven sand dunes the area in which these circles occur was originally the northeast peninsula of the Isle of Purbeck and a rather isolated place, not very accessible except by boat. There was a very narrow extension on northeastward to Gravel Point and from there a gravel spit. The area was the northernmost part of Studland Heath, north of the Agglestone and the Puckstone.

There are apparently no less than seventy-one circles in the area between Redhorn Quay and Jerry's Point (Gerry's Point on an old map). The diameters vary from 14 metres to 46 metres. The outer banks are only 0.3 metres high, but may be up to 6 metres across (Legg, 1987).

Part of a circle on the heath near Greenlands Farm, Studland, Dorset

There are six more circles to the south between Brand's Ford and Greenlands Farm. The enclosed surfaces, although slightly dished, are almost flat. Some of the banks have narrow gaps.

(Legg (1987) quoted the Royal Commission on Historical Monuments:

"Many held rainwater for short periods, displaying a wet bog flora; others are heath-covered. One or two circles with relatively deepcut interiors may have been ponds but the function of the others is quite unknown and their date only fixed between the Iron Age and c. AD 1700. The northern group are associated with thirteen low sandy mounds but these have also defied explanation. In the centre of the peninsula is a straight line of five regularly placed stones, originally standing upright, with a sixth N.W. of the N. end of the line."

Legg (1987) suggested that they were Roman or Medieval salt-pans. A possible problem for this theory is that much of the bedrock is permeable sandstone. I suppose that brine could be held by a thin clay layer. At present they are still a puzzle and are not fully explained! (Other theories include the former presence of oak trees in the centre, with acorns for pigs, but no access for ponies, for which they are poisonous: a certain answer to the qeustion of origin is not available at present.)

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Footnotes:

The Pirate's Route through the Little Sea:

The most famous of the 15th century privateers operating from Poole Harbour was the notorious Harry Paye. His headquarters were on Round Island and he plundered French and Spanish vessels and "Arripaye" was much dreaded by the Spanish. He burnt Gigon and Finisterra and carried off the holy crucifix from Santa Maria de Finisterra. Payne (1953) has said that local tradition is that Harry Paye could reach Round Island either by the normal route through Wytch Channel or by the South Deep Channel which is north of Ower. He further commented that the South Deep Channel could in those days be reached by sailing through the Little Sea which he had been assured was open at high water both to Studland and Brand's Bay. From the maps it is difficult to believe that this was possible, although a connection through to Bramble Bush Bay (adjacent to Brands Bay) might have been feasible at high water. Nevertheless, the Little Sea was in that century just a shallow part of Poole Bay and it is quite likely that Harry Paye did sail into some part of it from time to time.

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Oilfield Beneath the South Haven Peninsula

The Sherwood Sandstone Oil Reservoir of the Wytch Farm Oilfield, under Studland and Poole Harbour, Dorset

Beneath the South Haven and the North Haven Peninsula are important reserves of oil that are part of the Wytch Farm Oilfield. This oilfield is one of the largest onshore in northwest Europe, and is noted for its excellent record regarding the environment (BP have awards for this) and concealment. It is in the forests on the south side of Poole Harbour and almost hard to find! Part of the distribution of one of the reservoirs is shown on the map here. It is not actually a coincidence that the harbour entrance is so neatly positioned in relation to this reservoir (this is a good point for student discussion - Why is this? Clues - Cretaceous highs, Alpine inversion, buried river channel). The upper reservoir, not shown here, is in the Jurassic Bridport Sands and was discovered in 1974. More important now is the lower reservoir which is the Sherwood Reservoir in the Sherwood Sandstone of Triassic age. This was found in 1978. Exploration has progressively pushed the limits of this reservoir eastward and extraction now takes place not only in the Poole Harbour area but out to sea off Bournemouth. This is now done by an extended-reach borehole (horizontal and even upward drilling) from Goathorn Peninsula to somewhere off Bournemouth Pier. At one time there was a plan to build an artificial island on Hook Sand, offshore to the northeast of the South Haven Peninsula. There were protests regarding this and no developments in drilling technology proved it to be unnecessary. Now extraction of oil in Poole Bay is taking place without any oilfield facilities being visible (except at Goathorn). The environmental study in relation to this is in the excellent report commissioned by BP, the "Hook Island - Poole Bay - Private Bill - Environmental Study" (BP, 1991) .

Notice, incidently, that there are at least two wells under the South Haven Peninsula. These are not visible because these are merely the locations of the bottoms of deviated wells which bend eastward underground from a well-site on Goathorn Peninsula. Deviated drilling is extensively used at the Wytch Farm Oilfield and few wells proceed down vertically.

There have been no oil-spills from the Wytch Farm oilfield that have affected the South Haven Peninsula and it is very unlikely that the oil wells would affect this. Shipping accidents are a greater threat but no large oil tankers enter Poole Harbour. Extraction of oil from the reservoirs is controlled by reservoir engineers. Production rates and pressures in the reservoirs are regulated. In the upper reservoir, in particular, there is water-injection or the pumping down of water from Cleavel Point, Poole Harbour to maintain high pressures for extraction. The oil and associated gas in these reservoirs, is, of course, held in interstitial pore spaces between sand grains and not in an "oil lake" as some members of the general public sometimes think. Thus the removal of the oil does not cause major subsidence. Pressures may eventually be lowered as gas under high pressure is removed, although this is under the reservoir engineers' control. Brine of higher density inevitably progressively replaces oil and gas of lower density in the reservoir rock and this will change the stratal conditions under the South Haven Peninsula to a limited extent. Although the precise consequences of this are difficult to calculate and will only be known to the specialists of the oil industry, no large subsidence of the surface should take or have taken place and any slight depression, if there is any at all, may be difficult to detect. Although this is one of the many topics to be considered with regard to the future of the South Haven Peninsula, oil-extraction may not have a major effect, and probably less than the building of sea-defences at Bournemouth, the construction of the Training Bank, the dredging of the Swash Channel and its use by large ships, increased public use of the area, and the recent increase in rise of sea-level. Hook Island, if it had been built, might have had some consequence. It is to be noted, of course, that had there not been environmental interest and concern by the public and general improvement in environmental methods and protection, by now the South Haven Peninsula would have been a mass of houses and yachting marinas with a few oil installations in between them. (Here is another question for students: Compare the relatively natural South Haven Peninsula with a fully-developed or almost fully-developed sand spit in southern England. Eg. Weymouth).

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8.1 BIBLIOGRAPHY AND REFERENCES

Please go to the webpage on Studland and Harry Rocks; Bibliography and References.

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|Home and Contents |Studland - Tertiary Cliffs |Harry Rocks, Ballard Point |Swanage Bay |Studland and Harry Rocks; Bibliography |Sandbanks Peninsula

Copyright © 2014 Ian West, Catherine West, Tonya Loades and Joanna Bentley. All rights reserved. This is a purely academic website and images and text may not be copied for publication or for use on other webpages or for any commercial activity. A reasonable number of images and some text may be used for academic purposes, including field trip handouts, lectures, student projects, dissertations etc, providing source is acknowledged.

Disclaimer: Geological fieldwork involves some level of risk, which can be reduced by knowledge, experience and appropriate safety precautions. Persons undertaking field work should assess the risk, as far as possible, in accordance with weather, conditions on the day and the type of persons involved. In providing field guides on the Internet no person is advised here to undertake geological field work in any way that might involve them in unreasonable risk from cliffs, ledges, rocks, sea or other causes. Not all places need be visited and the descriptions and photographs here can be used as an alternative to visiting. Individuals and leaders should take appropriate safety precautions, and in bad conditions be prepared to cancell part or all of the field trip if necessary. Permission should be sought for entry into private land and no damage should take place. Attention should be paid to weather warnings, local warnings and danger signs. No liability for death, injury, damage to, or loss of property in connection with a field trip is accepted by providing these websites of geological information. Discussion of geological and geomorphological features, coast erosion, coastal retreat, storm surges etc are given here for academic and educational purposes only. They are not intended for assessment of risk to property or to life. No liability is accepted if this website is used beyond its academic purposes in attempting to determine measures of risk to life or property.

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Dr Ian West, author of these webpages

Webpage - written and produced by:


Ian West, M.Sc. Ph.D. F.G.S.

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at his private address, Romsey, Hampshire, kindly supported by Southampton University,and web-hosted by courtesy of iSolutions of Southampton University. The website does not necessarily represent the views of Southampton University. The website is written privately from home in Romsey, unfunded and with no staff other than the author, but generously and freely published by Southampton University. Field trips shown in photographs do not necessarily have any connection with Southampton University and may have been private or have been run by various organisations.
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