West, Ian M. 2014. Brighstone Bay and Compton Bay, Isle of Wight; Geology of the Wessex Coast. Internet site: www.Southampton.ac.uk/~imw/Wight-Brighstone-Bay.htm. Version: 14th August 2014.
Brighstone Bay and Compton Bay, Isle of Wight - a geological field guide

Ian West,

Romsey, Hampshire
and Visting Scientist at:
Faculty of Natural and Environmental Sciences,
Southampton University,

Webpage hosted by courtesy of iSolutions, Southampton University
Aerial photographs by courtesy of The Channel Coastal Observatory , National Oceanography Centre, Southampton.

|Home and Contents |Geology of the Isle of Wight - An Introduction |Alum Bay, Isle of Wight |Whitecliff Bay, Isle of Wight |Bibliography of Geology of the Isle of Wight

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A large dinosaur footprint, preserved in Lower Cretaceous, Wealden sandstone, Brighstone Bay, Isle of Wight, with Ian West for scale, 11 March 2009

Side view of a large dinosaur footprint, shown above, and preserved in Lower Cretaceous sandstone, Brighstone Bay, Isle of Wight, 11 March 2009

Reconstruction of an Iguanodon dinosaur making footprints in the carbonate sand of the Purbeck lagoon in early Cretaceous times

A natural sandstone cast of a footprint in mud of an herbivorous dinosaur of Iguanodon type, Wealden, Wessex Formation, Cretaceous, Isle of Wight, 11th March 2009

Another, tridactl, dinosaur footprint of an herbivorous dinosaur of Iguanodon type, Wealden, Wessex Formation, Cretaceous, Isle of Wight, 11th March 2009

A dinosaur footprint with partial impression of the hock, Ashdown Sands, Pett Level, Hastings, East Sussex, photograph courtesy of James Codd

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Safety and Risk Assessment

Falling Rocks
There is some risk of rock falls from the cliffs, even though, in general, they are not very high. Hard hats should be worn when studying in close proximity to cliffs.
Cliff Edge
There is a risk of falling from the eroding cliff if one was to approach too closely to the cliff edge. Climbing up from the beach may be hazardous.
Wave Wash
There is a risk during severe storms of being washed into the sea from a beach. At such times it may be difficult or impossible to get onto the beach, and no chances should be taken.
Tidal Range
The tidal range is fairly small here. However, risks should not be taken with regard to tide. There are certain places where trapping by the tide might occur. One of these is near the Upper Greensand outcrop in Compton Bay.
Other Risks
In very cold weather take precautions against hypothermia. Do not hammer hard splintery rocks. Beware of slipping on seaweed covered rocks. Health problems should be notified to field course leaders or project supervisors. Students undertaking mapping or research projects in the field should work in pairs for safety reasons. Conservation
Under no circumstances should dinosaur footprints be removed from the beach, except in the case of special permission. The coast here belongs to the National Trust and it is important that conservation here should be respected by parties and individuals.

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INTRODUCTION:

General

This webpage is to consider the geology and geomorphology of the coast of Brighstone (Brixston) Bay, on the southwest side of the Isle of Wight, near the village of Brighstone.

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INTRODUCTION:

Location Map, Geological Maps and Reference Books

Key reference books for use when visiting the Wealden strata of Brighstone Bay and elsewhere on the Isle of Wight

Location map for the Isle of Wight, old version, 1950s

Simplified geological map of the Isle of Wight

The 1926 geological map of Brighstone Bay, Isle of Wight, printed on the 1895 Ordnance Survey map

Location map for the Compton Bay to Sudmoor Point area, near Brook, southwest Isle of Wight, England

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INTRODUCTION CONTINUED:

Strata of the Isle of Wight and of Compton Bay and Brighstone Bay

Quaternary
- Holocene (Recent)
 
 
 
 
Landslips
Blown Sand
Tufa
Alluvium and Peat
Quaternary
- Pleistocene
 
 
 
 
Raised Beach
Valley Gravel
Plateau Gravel
Angular Flint Gravel
Palaeogene
   (Tertiary)
Solent Group
 
 
 
Barton Sand Formation
Barton Clay Formation

 
Bracklesham Group
 
 
 
 
 
"Bagshot Sands"  
 
Thames Group (London Clay etc)
 
Reading Formation
Bouldnor Formation (Bembr. Marls & Hamstead)
Bembridge Limestone Fmt.
Headon Hill Fmt. (Headon & Osborne)
 
 
 
 
Elmore Formation
Selsey Formation
Marsh Farm Formation
Earnley Formation
Wittering Formation
 
 
 
London Clay Formation
(Oldhaven Formation)
 
Cretaceous Upper Chalk
Middle Chalk
Lower Chalk  
 
Upper Greensand
Gault
 
 
Lower Greensand
 
 
 
 
Wealden Group (Wessex Formation and Vectis Formation)
 
 
(Purbeck Group. - in boreholes)
(Chalk with flints)
 
 
 
 
 
 
 
Carstone
Sandrock
Ferruginous Sands
Atherfield Clay
 
Vectis Formation ("Wealden Shales")
Wessex Formation ("Wealden Marls")
 
 
Jurassic
(Jurassic underground only)  

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STRATIGRAPHY - INTRODUCTION

WESSEX FORMATION (LOWER AND MAIN PART OF WEALDEN GROUP)

[section to be added]

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STRATIGRAPHY - INTRODUCTION

VECTIS FORMATION (UPPERMOST PART OF WEALDEN GROUP)

[section to be added]

[See particularly the key paper regarding sedimentology of the Vectis Formation:

Yoshida, S., Jackson, M.D., Johnson, H.D., Muggeridge, A.H. and Martinius, A W. 2001. Outcrop studies of tidal sandstones for reservoir characterisation (Lower Cretaceous Vectis Formation, Isle of Wight, southern England).]

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[END OF INTRODUCTION]

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LOCATION - COMPTON BAY

(including Shippards Chine or Compton Grange Chine, SZ378841)

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An oblique aerial overview of the western Isle of Wight, showing Compton Bay and Brook

View across Compton Bay, Isle of Wight, to Freshwater Bay with Chalk cliffs on both sides, 2008

Compton Bay, Isle of Wight, a general view of the geology, 2008

Compton Bay on the west coast of the Isle of Wight, faces towards the prevailing southwesterly winds. It is thus a place of rapid erosion and coastal retreat. The strata are all Cretaceous in this area, with the major units being the Lower Cretaceous Wealden Group, and the Chalk. Between the two there is Lower Greensand and Gault and Upper Greensand, well-exposed in the centre of Compton Bay.

There is a car park at Compton Chine (SZ368852), near Compton Farm, and this used to be used for easy access to the bay. However, recent cliff erosion has steepened the cliff. At many places on the Isle of Wight turned chines or access valleys into hanging valleys with steep cliffs at the foot. Access here will depend upon the state of the cliff at the time, and tide and weather conditions. It may or often may not be safe to descend here. It it not then access is possible, at least at the time of writing, at Shippards Chine (SZ378841) further to the southeast near Compton Grange (do not confuse Shippards Chine, near Brook, with Sheppards Chine, much further southeast and near Atherfield Point).

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LOCATION:

Compton Bay - Coastal Recession at Shippards Chine (Compton Grange Chine)

Coast erosion, southwest coast of the Isle of Wight - Shippards Chine car park, near Brook, 2008

Coastal recession at the car park of Shippards Chine, Compton Bay, Isle of Wight, March 2011

The southwest coast of the Isle of Wight has long been an area of major erosion. It is only about 10,000 years ago, at the end of the Pleistocene, since the valley of the English Channel was dry land. The rising sea level with wave erosion has destroyed large areas of soft Wealden strata. A substantial land area of Wealden clay and sands is now reduced to the relatively small southern part of the Isle of Wight. In due course, thousands of years ahead (a short time geologically, of course), Vectis will disappear, probably with the central Chalk ridge surviving last as some residual Chalk stacks and small islands. In the near future (in geological terms) the Military Road will be destroyed in part, and indeed some has already been lost at Blackgang. Shippards Chine shown above, is a place where the Military Road is very close to the cliffs; it might be broken through in merely a few decades (or even less). Such coastal retreat is quite normal, and fortunately there are very few buildings close to the cliff top in this region.

Compare the two photographs, which are of the same locality. The earlier one is from 2008 and the later from 2011. There has been a change and more of the car has been lost by the date of the second image.

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LOCALITIES

Compton Bay - Cretaceous Cliffs - View from Afton Down
(western Isle of Wight, near Brook)

Go also to: Geology of the Isle of Wight - General - Compton Bay

Aerial views of Compton Bay, Isle of Wight, 2004

The Afton Down and Compton Down road cutting in Lewes Nodular Chalk, Sternotaxis planus to Micraster cortestudinarium Zones, near Freshwater Bay, Isle of Wight, 2011

Road cutting in the Chalk at Compton Down and Afton Down, Isle of Wight, 2011

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LOCALITIES

Compton Bay - General Cliff Views

Erosion at Compton Bay, northwest of Brighstone Bay, Isle of Wight, May 2008, seen from Compton Grange Chine or Shippard's Chine

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Compton Bay, Isle of Wight, a general view of the geology, 2008

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Compton Bay, Isle of Wight, with a rough sea, March 12th 2012

Compton Bay is an important locality because it shows a section from the Wealden Group, Wessex Formation up into the Lower Greensand, the Gault and Upper Greensand, and then to the Lower Chalk. Parts of it, though, are obscured by landslide debris. The exposure is good because this locality, facing southwest, is subjected to major wave erosion. There is considerable contrast between the resistance to erosion of the Chalk, relatively harder, and the softer Wealden, LGS, Gault and UGS strata. The result of this is the Chalk cliff remains more or less in place, but with some retreat, while the cliffs of older Cretaceous strata move rapidly landward. Presumably at one time the Greensands etc were exposed as a cliff at High Down near the Needles and have been eroded back about 6.5 km.

The cliff exposures in Compton Bay can be accessed by walking at low tide from Shippards Chine. In the past it was possible to descend to the shore direclty at Compton Chine. Cliff erosion means that may not be possible now. If walking from Shippards Chine take care not to be cut off by a rising tide.

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LOCATION:

Compton Bay - Lower-Greensand

Isle of Wight

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LOCATION:

Compton Bay continued: Lower Greensand Succession

The following is a modified, and partially updated, version of an old log of the succession of the Lower Greensand at Compton Bay, based on White (1921), turn based on Bristow et al. (1889). This log is still valid, although the original thickness figures are given in old-fashioned feet and inches (1 metre equals 3.28 feet, or 1 foot equals 0.3048m; in round figures 3 feet equals 1 metre, and this will serve because the original figures will not usually be accurate to less than one inch.)

Compton Bay, Lower Greensand Succession

Monk's Bay Sandstone Formation "Carstone" (6 ft, 1.8m )[basal Albian]

Brown sand with a 3 inch (7.6cm) pebble-band at the base, containing rounded quartzite pebbles up to three-quarters of an inch in diameter, some phosphatic pebbles, and many pieces of wood. Cylindrical phosphate nodules also occur. [The base of this bed is the major, Late Cimmerian unconformity. At Sandown the equivalent pebble bed contains reworked Kimmeridge Clay fossils. In the northern Isle of Wight, as shown in diagrams above this bed rests unconformably on Upper Jurassic strata.]

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The Lower Greensand, Sandrock Formation and part of the Ferruginous Sands Formation, at Compton Bay, Isle of Wight, photograph April 1980 by Edward Bromhead

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Part of the Sandrock Formation, Lower Greensand, with the so-called Foliated Series, Compton Bay, Isle of Wight, from an old slide

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Sandrock Formation 81 ft., 6 inches [Upper Aptian]

Blue Clay .. 2 ft 6 ins.

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Pebble band with quartzites etc. - 0 to 3 ins.
Grey and greenish sand, with a layer of pyritised wood 8 and a half feet from the top, and scattered fragments near the top, about 12 and a half ft.
Pebble band as above, 6 inches.
Thickness of the above, including the two pebbles beds - 13 ft.
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Bright yellow sand with a ferruginous seam at the base - 10 ft.

Clean white sand and blue clay, interbedded in wavy laminae [rippled? flaser or linsen?], and producing copious chalybeate springs [ferruginous, sulphate-rich springs resulting from oxidation of pyrite]. ("foliated series") [of the old literature].

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Ferruginous Sands 251 ft, 6.5 inches (76.6m)
[in the brown part - oolitic iron ore, probably berthierine sands]

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LOCATION:

Compton Bay, Lower Greensand - Ferruginous Sand

The Ferruginous Sands Formation of the Lower Greensand undergoing rapid erosion at Compton Bay, Isle of Wight, old photograph

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Ferruginous sand of oxidised berthierine ooids, on the beach, Compton Bay, Isle of Wight

The Ferruginous Sands Formation of the Lower Greensand Group consist quite largely but not entirely of a "sand ironstone formation", like the Abbotsbury Ironstone (Kimmeridgian) or the Northampton Sand Ironstone Formation. In much of this brown sediments the grains are oolitic and now the iron is in oxidised limonitic state. Originally it was probably berthierine ("chamosite") as in the other iron ore deposits. The brown ooids fall to the beach in eroded material, and thus there is an unusual brown beach sand of oxidised berthierine ooids.

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LOCATION

Compton Bay - Chalk

Chalk cliffs at Compton Bay, Isle of Wight, in the early 1990s

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Chalk at Compton Bay - Introduction

The lowermost parts of the Chalk are exposed in the northwestern part of Compton Bay. It is really only Lower Chalk that can accessed without risk and even then only in appropriate tide conditions. The main cliff of Chalk first encountered in Compton Bay is Grey Chalk (i.e. Lower Chalk or Cenomanian). Further along and not easily accessible, the Turonian (Middle Chalk and base of Upper Chalk)is exposed. The cliff actually exposes Chalk as high as the Micraster cortestudinarium Zone (Lewes Nodular Chalk) but this is high and dangerous. Climbing on Chalk is not recommended; it can lead to fatal accidents.

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Chalk - Historic Introduction - Rowe

Arthur Rowe in 1908 made a detailed study of these and other Chalk cliffs of the Isle of Wight. He went to Compton Bay and the following is an extract from his comments. It is certainly not recommended that the dangerous traverse to Freshwater Bay, referred to be Rowe, is attempted.

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"The natural starting point for an examination of the White Chalk is Compton Bay, for its lowest beds are well exposed in a continuous section measuring nearly a thousand yards in length. The bay is always accessible at low tide, but there is one place which must be carefully watched, namely the projecting point formed by the chert-beds of the Upper Greensand, for here one may readily be caught by the tide. At low spring tidesd a good days work can be done before the returning water reaches the spot, but at neap tides the time allowed is quite inadequate. It is only at low spring-tides that access can be obtained to this bay from Freshwater Bay, and the usual course is to take the Military Road, hewn in the south side of Afton Down, to the cliff path west of Compton Chine..."

... The walk along the shore under Freshwater Cliff [to Compton Bay] is not one which we should take for pleasure, for the foreshore is a rugged tumble of large blocks of fallen chalk strongly reminiscent of the doubtful joys of Speeton. Much of the labour of climbing over this rough shore may be obviated in calm weather by taking a boat from Freshwater Bay and landing at low tide on the outer margin of the reefs, or at high tide on one of the rocks which fringes the coast. It can only be done, however, when there is a really smooth sea, and should not be attempted when there is the least swell.

Arriving at the shore [in northwestern Compton Bay] we pass over Gault, Upper Greensand, Glauconitic Marl, Chalk Marl, and the zones of Holaster subglobosus and Actinocamax Plenus. The Belemnite Marls [i.e. Plenus Marl at the top of the Cenomanian] are well-displayed in the cliff, and at times on the foreshore, and we had the good fortune to find an example of the name-fossil iin situ. The Belemnite must be very rare, since it is not recored in the "Geology of the Isle of Wight" (Memoir of the Geological Survey), nor in Vol. 2 of the Cretaceous Memoir. We found it also at Culver Cliff and in Man O'War Cove, South Dorset [west of Lulworth Cove]." [continues]

[A photograph of the Chalk cliffs toward Compton Bay taken from the Freshwater end is provided. A coloured geological maps of the zones of the Chalk at Compton Bay. See Plate B, Freshwater to Tapnell Down. Mucronata Zone (Portsdown Chalk Formation) is present north of Compton Bay (at East Afton Down), whereas it is absent at Freshwater, a local anomaly.]

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Cliffs of Cretaceous strata, and a landslide in Compton Bay, Isle of Wight, 2008

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Details of part of the West Melbury Marly Chalk Formation, at the base of the Chalk, Compton Bay, Isle of Wight, photograph by Edward Bromhead, April 1980

The basal part of the Chalk at Compton Bay in the Isle of Wight is what was formerly know as the "Chalk Marl" and is now named as the West Melbury Marly Chalk Formation. This has a considerable content of grey marl and thus it is quite different from the hard Cenomanian, Lower Chalk of Dorset (i.e. Lulworth Cove etc).

Insole et al. (1998) report that it has a rich fossil fauna including ammonites (Schloenbachia, Mantellicera, Acanthoceras), bivalves (Inoceramus, Pycnodonte), brachiopods, echinoids (Holaster), serpulids and sponges. Grey Chalk Member or Zigzag Chalk Member lies above. This is harder consisting of grey to white limestones with minor grey marl seams.

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LOCATION - HANOVER POINT

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HANOVER POINT

(West of Brook Village, SW coast of the Isle of Wight, Map Reference - SZ379836)

LOCALITIES:

Hanover Point Area (Compton Grange or Shippard's Chine to Brook Bay)

National Trust noticeboard at Compton Grange Chine or Shippard's Chine, southwest Isle of Wight

Red overbanks clays and silts of the Wealden river, Wessex Formation, between Compton Grange Chine (Shippard's Chine) and Hanover Point, Isle of Wight, 4th May 2008

Members of the southampton University Geological Society hunt for dinosaur bones in the Wessex Formation, Wealden, Lower Cretaceous, just northwest of Hanover Point, Isle of Wight

Dinosaur bones are sometimes washed out onto the beach from the Wealden cliffs of the Isle of Wight, and a search commences here, near Hanover Point, 4th May 2008

Liquefaction phenomena in the lower part of the a fluvial sandstone in the Wessex Formation of the Wealden at Hanover Point, Isle of Wight, 4th May 2008

Cross-lamination in a fluvial sandstone sof the Wessex Formation, Wealden, near Hanover Point, Isle of Wight

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Hannover Point

The Pine Raft

The so called Pine Raft, fossil coniferous tree trunks, in the Wessex Formation of the Wealden Group, Hanover Point, Isle of Wight, old photograph, colour-corrected

The "Pine Raft" at Hanover Point near Brook consists of gymnosperm tree remains that can be seen at low tide. They come from a Wealden plant bed. The tree remains are either compressed or in solid uncompressed form, as in the case of tree trunk shown above. Examples like this one have been impregnated by calcite at a very early stage, and thus have avoided compaction.

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LOCATION:

BRIGHSTONE BAY

Brighstone Bay is about 9 km. long. It extends from Hanover Point to Atherfield Point. It is mainly of Wealden strata and is a notable area for collecting dinosaur bones. There is access to the beach from several chines or small stream valleys, but the details of these may change with coast erosion. In general chines are now being progressively cut back, and with time, access to the coast will become more difficult. If exploring this stretch of coast, find out the tide conditions in advance and arrange your visit at low tide. There may be real difficulties at high tide and in stormy conditions.

The Barnes High Sandstone of the Vectis Formation, Wealden Group, near Shepherds Chine, Isle of Wight, about 1992

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LOCALITIES:

Sheppard's Chine to Barnes High (northwest of Atherfield Point)

The Barnes High Sandstone of the Vectis Formation, Wealden Group, between Cowleaze Chine and Barnes High, Brighstone Bay, Isle of Wight, 11th March 2009

The Barnes High Sandstone of the Vectis Formation, Wealden Group, near Shepherds Chine, Isle of Wight, about 1992

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ACKNOWLEDGEMENTS

I am particularly grateful to Edward Bromhead for copies of his superb photographs from Compton Bay. As with other webpages the kind cooperation of Southampton University, who run this webpage on their server, is very much appreciated. I thank the Dean of the Faculty of Environmental and Natural Science, Professor Stephen Hawkins, the Deputy Dean, Professor Jonathon Bull and the Head of Ocean and Earth Sciences, Professor Rachel Mills for supporting this website.

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|Home and Contents and List of Webpages | |Field Guides - Introduction |Bibliography of Geology of the Isle of Wight |Bibliography of Geology of the Solent Estuarine System |Geology of the Isle of Wight - An Introduction |Alum Bay, Isle of Wight |Whitecliff Bay, Isle of Wight

Copyright © 2014 Ian West, Catherine West, Tonya Loades and Joanna Bentley. All rights reserved. This is a private, academic website intended to be useful for research, reference and educational purposes. Images and text may not be copied for publication or for use on other webpages such as MOOCs or for any commercial activity. A reasonable number of images and some text may be used for non-commercial, non-charged, non-online and non- published academic purposes, including field trip handouts, student projects, dissertations etc, providing the source is acknowledged. All images so used must contain the original caption, including the copyright statement. Some images are not those of the author and the copyright is that of the original photographer and these are not for any use without specific permission from the source photographer. This particularly applies to aerial photographs, but also to some sets of field photographs.

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.