Kimmeridge Clay and Kimmeridge Bay
Because of the hazard of rock falls and it is a dangerous place to visit unless it is well understood and proper precautions are undertaken. The cliffs are vertical and high and subject to erosion by the sea at the base. The shale and mudstone is full of joints and fissures and not stable. Small pieces will tumble off from time to time as you walk along.
More serious are substantial falls like the one shown above. These may occur without warning; suddenly there will be a loud crash and a plume of debris and dust. These happen particularly in certain weather conditions, such as when there is frost or rain and sometimes when the shale has dried in the hot sun. If you are out on the low tide ledges falling debris would not usually reach you but there is no guarantee of safety. The risk is greatest where the cliffs are highest, where there is joint separated shale above and where there is evidence of a recent fall in the form of shattered debris.
A photograph of Maple Ledge Fault (below), illustrates the risk even in fine, dry weather. Geologists should keep out from the cliffs as far as possible, although geological study does require close examination of the cliff at intpatagonia better sweater women'servals. These should be kept short and only take place after examination of the cliff above. Geologists, although by the nature of their interests and activities are not free from risk. However, they would not generally do what some holiday makers do, that is sit at the foot of a Kimmeridge Clay or other vertical cliff. This is very unwise. If you want to sit for a lunch break, perhaps, then sit out on a ledge away from the cliff. The worst cliff accident on the Dorset coast took place at
Lulworth Cove in the 1970s to a group that was sitting at the foot of a cliff.
The cliffs in the Kimmeridge area are mostly vertical and from time to time shed debris which descends at high velocity. At all localities beware of falling debris and do not hammer or dig out the cliffs. This is very hazardous because the falling shale or dolomite could easily have fatal consequences. Keep away from the foot of the cliff and wear safety helmets. Do not sit at the foot of the cliffs, although, unfortunately, this is sometimes foolishly undertaken by non geological visitors to Kimmeridge Bay. The higher cliffs to the east are even more dangerous than those in Kimmeridge Bay. You can walk some way westward in Kimmeridge Bay and you can study ledges of the Flats Stone Band. The western extremity of the bay though is in the Army firing ranges and you should abide by the army safety warning notices.
You need low tide to travel far along the cliffs to the east and there is danger of being cut off there if care is not taken. There is a tidal trap just west of Clavell s Hard and you can easily go beyond this at a low spring tide. You may have about two hours maximum to explore east of Clavell s Hard. It is also worth noting that low tide is preferable on all the Kimmeridge coast because not only does it reveal more of the ledges but it allows the visitors to keep further out from the cliffs. High tide may push them back too close to the foot of the cliff and into the hazard zone.
Take care on the beach and ledges bepatagonia guide jacket blouse2cause the shale can be very slippery. Obviously when above the cliffs one should not approach the cliff edge which is quite abrupt. Do not handle or interfere with any metal objects that might be connected with the army firing activities. Do not attempt to climb the shale cliffs; there is no route up except at the obvious footpath access points. Because this website is on geology, safety regarding marine activities is a separate matter not dealt with here. Many, though are from informal, private coastal walks, or from private, research field trips. The photographs are for geological purposes only and are there to show rocks, not people or techniques. They are not intended to show safety procedures and no activities shown are necessarily intended to be copied. This website is about geology for geologists. The cliff, sea, tide and weather conditions vary greatly so always make your own assessment of the cliffs and conditions on the day, and arrange your coastal procedures in accordance. Always consult tide tables before field work at or near Kimmeridge. No responsibility at all is taken for any activities of field parties or individuals going to the Kimmeridge coast for their own purposes or objectives. As at other geological sites a risk is present and the possibility of an accident, although a rare occurrence, cannot be eliminated.
Sir William Clavell organised the working of the Kimmeridge oil shale and used it as fuel for glass making and for boiling sea water to manufacture salt. He was also involved in the production of alum. Clavell s Hard is an oil shale mining site on the cliffs to the south of Smedmore House House, and this is a familiar to many geologists. The oil shale or Kimmeridge Coal used in the industry may have come from the cliff top near Cuddle or it may been quarried by Clavell s workers from Clavell s Hard (as it was mined there in the 19th century).
For more on the oil shale and its use in the production of alum and information on Clavell s Hard see my associated webpage on:
Geology of the Isle of Purbeck is shown on an old map (part of a map modified patagonia m mixed guide hoody 84080from Damon (1884). Modern changes in the geological mapping of the arpatagonia outlet store freeport maineea have only been of detail. Note an older spelling of Kimeridge with one m .
A map above shows the simplified solid geology of the Kimmeridge area and locations referred to in this and associated Kimmeridge field trip guides. The area shown on the map is one in which Upper Jurassic and Lower Cretaceous strata generally dip northward within the Purbeck Monocline. The major, regional, anticlinal axis is east west, offshore south of Kimmeridge, although a local complication is the Broad Bench anticlinal axis which is at an appreciable angle to the main fpatagonia employee purchase programold axis. Structure is also complicated by a general plunge of the Purbeck Monocline to the east. The positionpatagonia hiking new zealands of most of the cliffs near the axis results in a low dip for much of the stretch of coast. The dip steepens (northward) in Brandy Bay and also inland around the villages of Kimmeridge, Steeple and Kingston. The oldest strata visibpatagonia guide jacket blouse3le, part of the Lower Kimmeridge Clay Formation, is exposed on the west side of Kimmeridge Bay . By walking along the coast eastward from here progressively higher parts of the Kimmeridge Clay are seen. The highest beds are seen at Egmont Bay, Hounstout Cliff and Chapmans Pool. West of Kimmeridge Bay progressively higher parts of the Kimmeridge Clay occur in a northwestward direction in Brandy Bay. This is within the Army Firing Ranges and the foot of the cliffs is not normally accessible. When the ranges are open, however, the cliffs can be seen to some extent from a footpath above.
Car or minibus access is easy, through a private toll road of the Smedmore Estate. Bringing coaches to Kimmeridge is possible but requires written permission from Dorset County Council in advance, with details and time of the specific visit. The road is narrow and has width restrictions. The pass must be in the possession of the coach driver when arriving.
Note that the Army Range starts west of Kimmeridge Bay and access to this is only on the Range Walks, which are open most weekends and at some other times. Obviously do not touch any shells or other dubious metal objects.
The approach is through Kimmeridge village and on to the beginning of a narrow, private, toll road belonging to the Smedmore Estate. The narrow road is suitable for cars and mini buses but there is no access for full size coaches or buses (although in special cases application can be made to Dorset County Council and also to the Smedmore Estate for a coach permit). Payment is at a hut at the entrance to the toll road, although there not always a toll collector present in winter. You can park in the central car park shown and descend to the beach at the ravine at Gaulter Gap. You can almost always walk down onto the beach of Kimmeridge Bay but low tide is preferably.
As mentioned above, you will need low tide topatagonia outlet store nj travel far along the cliffs to the east and there is danger of being cut off. You can walk some way westward in Kimmeridge Bay and you can study the Flats Stone Band. The western extremity of the bay though is in the Army firing ranges and there is no access along the beach west of the bay. There is, however, a cliff top path which is open when the Range Walks are open (usually at weekends and certain holiday periods).
Although this is a geological field guide, it is worth mentioning that there is a well known mapatagonia better sweater grayrine nature reserve at Kimmeridge (see website:
Purbeck Marine Wildlife Reserve). You can visit thepatagonia guide jacket blouse0 Marine Centre which is amongst the black fishermen s huts at the southeastern corner of Kimmeridge Bay. Boat and diving enthusiasts congregate here, and there is separate parking at this end for boat owners.
An interesting aspect of Kimmeridge Bay is that in the past (up to about the 1990s) there were very large accumulations of rotting seaweed. The reason for this is that there are many offshore ledges or reefs of dolomite and hard bituminous shale, and the seaweed grows on these. In 2011 there now seems to be much less accumulated dead seaweed. This has been noticed elsewhere, as in the Torquay region.
When there is abundant rotting seaweed, it gives off a characteristic odour that some people think is a smell of oil from oil shale (there is a minor smell from oil shale, but it is far exceeded by the seaweed). The seaweed smell is not particularly unpleasant or particularly noticeable to everyone, but some local people have an impolite name for the northeast corner of Kimmeridge Bay. When the seaweed is trodden on in summer or autumn large swarms of seaweed flies (Coelopa frigida) rise from the beach. This is a harmless fly of rather crab like appearance that is of little inconvenience to geologists.
The soft rotting seaweed and flies also can also occur in abundance to the east of Kimmeridge Bay, particularly in the Cuddle area. Occasionally when walking in this area on a hot day the flies are a minor nuisance and it is good to get onto hard rock. In general the flies add interest and character to the Kimmeridge coast and their worm like larvae help in the decomposition of the seaweed. I am not aware of any harm having occurred at Kimmeridge from the rotting seaweed, but it should be noted that on the French coast a horse has been killed by H2S from rotting seaweed and a rider taken to hospital. In cold, windy or stormy weather you will encounter no problem with flies. In general the flies are a good safety factor because they deter summer holiday makers from sitting on the beach beneath the hazardous cliffs.
To commence a general field trip, park the car in the main car park on the cliff top. Have a look over the cliff, without going too close to the edge (unstable shale). Dark cliffs of shale, and ledges of stone projecting into the sea. You may notice the smell of seaweed, and sometimes in summer an odour of warm oil shale. You can commence study of the bay by looking at the notice boards and then walking down the steps into the Gaulter Gap ravine (centre of the bay), across the little bridge and down onto the beach. A small part of the bay is often accessible even at high tide, but low tide conditions are much better and tide tables should be consulted prior to a field trip.
These photographs show Gaulter Gap, where the Lower Kimmerige Clay is exposed. The path into Kimmeridge Bay from the car park on the cliff top at the centre is alongside a small ravine with a stream. Rejuvenation of the stream valley has occurred aspatagonia everlong review xc60 a result of rapid cliff retreat and this has formed the ravine within the broader valley. In the distance is Clavell s Tower above Hen Cliff. At the mouth of the ravine you can see the Lower Kimmeridge Clay (of the Aulacostephanus autissiodorensis ammonite zone see Cox and Gallois, 1981). If you turn right at the bottom you will see the cycles of sedimentation shown in the next image and also the Washing Ledge Stone Band.
Some erosion of the shale has been taking place here (compare older and newer photographs). The concrete Dragon s Teeth were placed here to prevent invasion by German tanks from landing craft during the Second World War. There would have been barbed wire and mines here too then. Although erosion is taking place, the survival of the Dragon s Teeth from the 1940s shows that ipatagonia guide jacket blouset not at a very high rate just here. The Kimmeridge Clay is always crumbling in the cliffs and the calcareous, less bituminous parts break into small pieces. The bituminous shale is rather more resistant but a major feature are ledges of stone band dolomite, the Kimmeridge Ledges, extending some way out to sea (many ships have been wrecked on them). These ledges break the waves and protect the coast to some extent. Unfortunately, the tide was fairly high at the time of the photograph so they are not visible (but can be seen in the left image). This particular location at the back of the back of the bay is also less exposed than elsewhere.
Presently a little open coombe gives a glimse inland of some ugly coastguard houses, partly screened by a grove of straggling trees, and turning this way, but keeping on the turfy hillside, we open Kimmeridge Bay itself. The view is very quaint: its foreground composed of the sloping down, near the foot of which lie the objectionable houses [at Gaulter Gap], while on the summit stands a curious circular tower [Clavell s Tower] of dark stone [Kimmeridge dolomite], with a parapet of lighter tint, and encircled at its base with a colonnade supporting a balcony, whence a charming and extended landscape is visible, for the sake of which, no doubt, this not ill designed Belvedere was erected. Northward, a mile or more away, in a vast curve receding by hollow slopes from the sea edge, rises a lofty range of hills, grassed over to the very crest. Hill and dale, nearly treeless, are vested in a garment of brilliant emerald, only blue green glimmering waters of the miniature bay, fringed with low but steep shores of dingy shale, and more distant, the magnificent stone yellow precipices of Gad Cliff, with the chalken heights round Worbarrow Bay break the verdant mononoty of hue.
The Kimmeridge Clay Formation is largely, but not completely exposed at the surface at Kimmeridge (Arkell, 1947). Thus the thickness cannot be directly measured. Seismic reflection profiles by British Petroleum Ltd have shown that the full thickness is between 535m and 585m in this area (Gallois, 2000). Measurement is further complicated by lateral changes in thickness. Cox and Gallois (1981) should be consulted as the key publications on the stratigraphy, with valuable additional data coming from the new borehole investigations of the RGGE (Rapid Global Geological Events special research project of NERC) as described by Gallois (2000). This new work, in addition to providing detailed data for cyclipatagonia jewelry 2 giftcity studies, has revealed what strata lie unexposed beneath Kimmeridge Bay and it has also clarified the details of the upper part of the succession.
The Kimmeridge Clay represents the clays sediments of the sea for approximatelpatagonia guide jacket blouse1y 8.5 million years (Gradstein et al., 1994).
