West, Ian M. 2013. Dancing Ledge, Isle of Purbeck, Dorset, and Adjacent Cliffs; Geology of the Wessex Coast of Southern England (UNESCO Dorset and East Devon World Heritage Coast - Jurassic Coast). Geological field description and virtual field trip. Internet site: www.southampton.ac.uk/~imw/Dancing-Ledge.htm. Version: 25th July 2013.
Dancing Ledge, Dorset, and adjacent cliffs of Jurassic Coast - geological field guide; Geology of the Wessex Coast

Ian West,
Romsey, Hampshire

and Visiting Scientist at:
Faculty of Natural and Environmental Sciences,
Website hosted by iSolutions, Southampton University
Aerial photographs by courtesy of The Channel Coastal Observatory .
Website archived at the British Library

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A view of the Portland Stone coast around Dancing Ledge and Blackers Hole, near Swanage, Isle of Purbeck, Dorset, from Winspit in 2007

A view of the Dancing Ledge Portland Stone coast, near Swanage, Isle of Purbeck, Dorset, New Years Day, 2013

A view from the sea of Dancing Ledge, Isle of Purbeck, Dorset in 1989, photography by Gareth Lloyd

Dancing Ledge, near Swanage, Isle of Purbeck, Dorset, a general view from the top, 18 September 2007



St. Aldhelm's Head to Durlston Head, Jurassic Coast, Isle of Purbeck - Other Webpages

Location map showing the locations for webpages for the coast between Durlston Head and St. Aldhelm's Head, near Swanage, Isle of Purbeck, Dorset

St. St. Aldhelm's Head...
Winspit, Seacombe..
Hd - Anvil Point to Blackers Hole
St. Aldhelm's Hd to Anvil Point - Bibliography More Related Field Guides and Bibliographies ---

| Durlston Bay -Lower Purbeck | Durlston Bay Bibliography | Purbeck Formation Bibliography | Purbeck Palaeoenvironments | | Durlston Head, Isle of Purbeck |St. Aldhelm's Hd to Anvil Point - Geological Bibliography |Durlston Bay - Peveril Point, Upper Purbeck Formation |Durlston Bay, Middle Purbeck Durlston Bay - Lower Purbeck |Durlston Bay - Central Zigzag Part & Coast Erosion |Durlston Head - Lower Purbeck Formation & Portland Stone |Durlston Bay - Bibliography |Portland - General |Portland Bill



INTRODUCTION TO DANCING LEDGE, JURASSIC COAST:

General

In the eastern part of Jurassic Coast World Heritage Site, Dancing Ledge is a notable feature. This is a large gently sloping ledge of part of the Portland Cherty Series, with a large abandoned quarry above. It has been said to have received its name from the appearance waves "dancing" on the ledge (although this is not particularly noticable) or because the sea ledge was humourously suggested to be as big and flat (but not smooth) as a dance floor ( Bruce, 1989). Actually, as mentioned below, there seems to have been dancing on the ledge with the help of brass band. The brass band certainly played, as the author who mentioned this was a member of the band () Hardy (1910). This is odd because a worse place for dancing, i.e. on the uncomfortable Prickle Bed, could hardly be chosen. The name "Dancing Ledge" was probably in use long before the brass band entertainment. Although there is no specific evidence for this, it may be more probable that the name is some corruption of a reference to the springs which lead to water trickling over the cliff near here. Immediately to the west of adjacent Green Point. The wet, slimy cliff is unusually dark - thus - "Dark Spring Ledge" was probably the original name.

In addition to this present water flow, at one time some fresh water may have trickled seaward at this very locality, rather than just to the east of it. As mentioned below there is a vertical pothole, a small vadose zone cave feature that is obviously the result of downward flow of water from the Purbeck clays above (perched aquifer) down through the Portland Stone.

The upper, quarried ledge has some adits or galleries, mostly (but not all) now partly closed, and some old piles of quarry debris with some fossils. The area is used for the training of rock climbers. A bathing pool has been quarried out of the lower ledge for Durnford Preparatory School.

The quarry, cliffs and ledge here provide a good section through the upper part of the Portland Cherty Series and through the Portland Freestone. Fallen blocks of stromatolitic limestone come from the basal Purbeck Formation above. Ammonites can be seen, various features of silicification are clear, sponge spicules can be seen in the chert, bivalves in the Portland Freestone are common. There is a small karstic cave and interesting travertine features. Cave development by the sea can be studied. To the east of Dancing Ledge is a significant fault affecting the cliffs and the topography just inland. A dry valley with hillwash deposits descends to the quarry, and the topic of former water flow in the area is of interest. Jointing in the Portland Stone is also interesting and could be studied and assessed by statistical methods as part of a student exercise.

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INTRODUCTION - continued:

History of Dancing Ledge, Jurassic Coast

The quarry is very old and is peculiar in that it is probably the largest cliff quarry in Dorset without any road access. The limestone quarry provided good building stone from the Under Freestone Bed only of the Portland Limestone Formation and in addition various rock for sea walls, particularly at Ramsgate. This work took place a long time ago and the quarrying was finished and the place much as it now by mid Victorian times.

Seaward and lower than the old working quarry is a a large natural sea ledge, an original promontory formed by the Prickle Bed, J', of the Portland Chert Member of the Portland Stone Formation. The Prickle Bed dips to the east and descends below sea-level (which rarely happens elsewhere). Now the Prickle Bed is notable for being the most bioturbated, crab-burrowed part of the Portland Chert Member. As a result it is non-uniform and connected by linking burrows. Because of the near-randomness of the burrow system the cementation has been extremely irregular. Thus the rock does not behave in a uniform manner and it only has joint at wide spaced intervals; it is not prone to close jointing. Thus the bed is thin but strong and relatively resistant to wave action. Dipping into the sea it forms a "Hard", a landing area for boats. There is a similar situation on a smaller scale at the cliff quarry of Kimmeridge oil shale at Clavell's Hard. That quarry and set of mines, like the quarry and mines of Dancing Ledge has no road connection. Perhaps both Clavell's Hard and Dancing Ledge represent sites of early quarrying for sea transport before many roads reached the coast in this region.

When the quarry was abandoned it became a place for smuggling and for visiting, swimming and othjer recreation. Rock climbing there has been a more recent development. Some notes regarding non-geological activities here follow.

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INTRODUCTION - continued:

More Historical Notes about Dancing Ledge

An old photograph of Dancing Ledge, near Swanage, Isle of Purbeck, Dorset, after Hardy, 1910

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Visit of the Prince of Wales, the Future King Edward VII, to Dancing Ledge

[Supplementary historical notes, based on Hardy (1910)]

On September 26th, 1856, H.R.H. the young Prince of Wales, the future King Edward VII, travelling incognito, stayed at the Royal Victoria Hotel, Swanage. This had received its name after Princess Victoria (when she was 14) stayed there in October, 1833. The Prince of Wales was only 14 years old. When the Prince arrived at the hotel he was unrecognised by the proprietor, Mr. William Hixon. The boy and his two gentleman companions told Mr. Hixon that they would need three beds. The hotel was almost full so the proprietor told them that he could only let them have two beds and the young gentleman, the boy, could sleep on the sofa. Edward did not give away his identity and he did spend the night on the sofa. It was only later when Mr. Hixon received a cheque signed by HRS, the Prince of Wales, that he realised that he had made a terrible mistake!

As they slept in the hotel that night, close to the coast, stormy weather started. About midnight a sever gale sprang up with heavy seas causing much damage to the fishing boats in Swanage Bay. The next day the young Prince Edward wanted to walk the coast from Swanage to St. Aldhelms Head and on to Kingston. This is a long and energetic walk and he must have been very fit! No doubt that the weather was still windy, especially out on the cliffs. Edward's luggage was sent in advance to the Eldon Arms, Kingston to await him. This hotel is still there, now known as the Scott Arms. It is conpicuous on the corner of Kingston and well known to visitors today. It has a good view northward to Corfe Castle. It takes its new name from the same man - John Scott, the First Lord Eldon, and owner of Encombe House and the great Encombe Estate.

The distinguished party at Swanage then set out to walk along the coastguard track westward. This footpath, as it is now, was narrow, winding, and involves descending and ascending the slopes of various valleys and hills (total ascent and descent of about 300m or 1000ft). At that date it was marked nearly the whole distance by white-washed stones, as a guide for coastguards patrolling at night. You can still walk Prince Edward's route, and for most of the way you will be on exactly the same soil. This path is now part of the modern South West Coast Path (traversing part of Jurassic Coast). The path is well-worn now but there are no white-painted rocks, as it is rarely traversed at night now.

In choosing this path Edward selected seven and a half miles (12km.) of the best rocky scenery to be found on the South Coast of England. He began with Durlstone Bay and Durlstone Head, at that date with far fewer trees than now. At Durlstone Head was the Castle and Globe of Mr. George Burt of Swanage. This looks the same. So the Prince almost started his cliff walk at what is now a Gateway to Jurassic Coast . From Durlston Head, he passed Round Down, with its ancient signal house, and then on past the Blackers Hole area to Dancing Ledge. The royal rambler (or "Royal pedestrian" in Hardy's language) could see the various ancient cliff quarries on this route. They still had at that date their antiquated lowering machinery, consisting of windlass and gibbet (illustrated elsewhere in this webpage). The Prince reached the large cliff quarry known as Dancing Ledge. He then went on from there and followed the coast path to St. Aldhelm's Head. From this promontory he continued on past Emmetts Hill to Chapman's Pool. He then walked up the coombe or valley to the village of Kingston and his destination at the Eldon Arms.

Edward was the first Prince of Wales to visit the "Jurassic Coast", as it is now known. The present Prince of Wales, Charles, opened the "Jurassic Coast" in 1992 at the eastern end near Exmouth, and then travelled by helicopter to a reception at Lulworth Castle, not far away from Swanage.

Hardy (1910) commented further about Dancing Ledge.

"A Picnic on Dancing Ledge

Then the romantic spot named Dancing Ledge was reached [by the Prince of Wales during his trip], where a picnic was once organised by the Rector and Lord of the Manor, The Rev. G.V. Garland and Mr. S. Serrell, of Langton. This outing took place on the flat rocks below, where a plentiful repast, consisting of lobster tea, salad and liquid refreshment, was indulged in. At one o'clock the feast began, accompanied by the strains of the Swanage Brass and Reed Band, of which I was a member.
After the lunch dancing followed until six o'clock [Where exactly did they dance? If the "flat rocks below" means the lower, Prickle Bed ledge, it would have been impossible to dance there, because of the very irregular surface. Perhaps the reference is to the quarry floor, which is reasonably flat.] Then the the rev. gentleman reminded them that the time of departure and return was drawing nigh, and proposed the usual toasts, including the health of the Queen and the 'Squire, who also proposed the health of the rector.
Then the band struck up "For He's a Jolly Good Fellow," and after three times three, they all commenced to climb the cliffs; but amongst them were a few ladies who were not expert at scaling the rocks, although assisted by gentlemen in front and behind; and, as such repeated acts of "backsliding" were observed by the Rector, he asked the bandmaster if he could play a suitable tune to enliven the proceedings and to encourage the inexpert ladies to hasten their ascent. The bandmaster answeredd "I will play any tune you like, sir" whereupon the Rector replied "Play 'Such a-getting upstair I never did see'". It is hardly necessary to add that this lively tune had the desired effect, and that all the party reached the top safely at least and wended their way homewards, thoroughly delighted with the their day's outing. Since the das mentioned above a capacious swimming tank has been hewn out of this rock for the use of the pupils of Durnford School."

Hardy (1910) also wrote this about Dancing Ledge.

"The Gull Shooter Shot [at Dancing Ledge]

The Rev. George Taylor, M.A., was curate of Langton [Matravers] in 1834. He lived with his father, the Rev. William Taylor at Magnolia House, Swanage, and used to drive [by horse and carriage] to Langton to do duty. One day he and his brother John took their father's yatch and sailed round the back of the cliff near Dancing Ledge with the object of shooting a few seagulls. He was in the cabin and his loaded gun was lying on the bed. His brother shouted down to him to bring the gun quickly as their was a good shot. Seizing the muzzle in his hand he turned to run up on deck, when the trigger caught in the bedclothes and the full charge went up his arm. There was scarcely any wind at the time, so it took them a long time to get back to Swanage. In those days ordinary people knew little about "ambulance work" or "first aid", and so the young man nearly bled to death. He survived only a few weeks and died at the early age of 26."

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INTRODUCTION continued:

Dancing Ledge - Historical Notes continued:

Smugglers Carry Tubs from Dancing Ledge to Spyway Barn and Langton Church

Hardy (1910) wrote this about smuggling at Dancing Ledge.

At one time there were a number of people in Langton [Langton Matravers, up the hill from Dancing Ledge} and the neighbourhood well known to be great smugglers. About 1830 an exciting incident happened at the church [The church at Langton Matravers is only 2km directly north of Dancing Ledge, up the hill, and almost opposite Durnford Drive].
Most of the smugglers' hiding places had become well-known to the Coastguards. Another place had to be found somewhere. So a few Langtonian smugglers had a consultation, and one of the head ones thought that he knew a first-rate place, which was over the ceiling of the church in the apex of the roof. This place was reached by going up inside the tower. This new place was used for smuggling for a long time before it was discovered.
One dark night they were expecting a cargo of tubs at Dancing Ledge. The ganger [the foreman or gang leader of the smugglers] and his men were all on the Ledge watching for their craft. They had not to wait long before she came. They got the tubs [of brandy or gin] ashore all right, and away went the boat to sea in the darkness. The smugglers were glad to see their tubs landed safe without the Coastguards seeing them. They were men of different callings - quarriers, masons, labourers, shepherds etc.

The ganger said to them, "Now my lads, I can see very clearly that we shall not be able to get this big freight of tubs stored in the church tonight, seeing that all our men have not turned up. We shall have to stow them in some spot near the church. I do not know what to do."

Spyway Barn, on the path to Dancing Ledge, from Langton Matravers, near Swanage, Dorset, a place where smugglers tried to hide their tubs

Then a quarrier suggested putting the kegs in an old quarry near Spyway [photo above, and see the old Purbeck stone quarries, shown on the OS map, near Spyway Barn, up the hill]. Some did not agree with this place because it was wet and dirty. At last the Ganger said to a farm labourer "Come, Tom, don't you know a place handy? We have taken your advice before and it has been all right." "Yes", said Tom, "I know a good spot down at Spyway Barn. Pack them over with some straw." "Oh!" they said, "the coastguard will be bound to find them there." "No," said Tom, "I will take good care of that. I will open the bullhouse door and let the bull out night and day all the time they are there. As you know, our bull is a terror to the neighbourhood, and no one will ever go near him - not even the brave Coastguard with the brace of pistols, cutlesses, muskets and fixed bayonets." "Very well" said the ganger, "we will take your advice Tom." Before they began to work, they sat down [on the rocks at Dancing Ledge] and drank some of the hot stuff to spur them up over the cliff. Afterwards they went to work like dragons, first having placed two watchmen, one on the east and one on the west [of the old quarry]. They got their tubs all up over the cliff and down to [up to?] the barton at Spyway, where they left them in the custody of "John Bull". [a barton was an enclosed courtyard in which were enclosed hayricks and other farming and general stores associated with farming]. Spyway Barn is a farm and so probably the barton was a stone-wall enclosed field associated with the farm]. After that the men sat down and finished the remainder of the spirits left in the little keg that they had opened on Dancing Ledge. Then they all went home to bed and did not get up before twelve o'clock next day.

The next evening they were all summoned to the private room of the Kings Arms [this pub is still there - 27 High Street, Langton Matravers, Dorset] to devise plans to finish the job. The ganger said "We must have a different from last time, for although it was very dark we only just escaped capture. We ought not have unloaded the waggon in front of the Church. This time we must get to the tower another way." One said that they might bring the waggon down Durnford Road [Durnford Drove - see map] and get through the garden at the back of the house and through a small door west of the tower. [This seems to be a discussion of the gardens of Durnford House, before it became the spartan Durnford School in 1894, and was later attended by Ian Fleming, author of the James Bond novels. The school was notorious for its morning "strip and swim" rituals in the cold bathing pool at Dancing Ledge!]
The ganger answered "That is a very good plan; but I see two great lions in our way. First there is old John the gardener. He will tell the Squire everthing and a little more." "Leave him to me" said the landlord who was a bit of smuggler himself, "I will get him to leave the garden gate unlocked. I know the way to square old John. "Well," said the ganger, "That is one lion dead. What about the other?. There is a great dog whose kennel is close to the door." At this the shephard spoke up and said "I can kill that lion, for I had a sheep die the other day, so I can give that dog something to do for an hour." Then said the ganger "I think that this plan will do very well. We must all meet at the barton to-morrow night." So they all met at Spyway, loaded up the waggon, putting a little straw on the top, and at last the tubs were safely stowed away in the church. Nothing happened until three weeks after, when it was thought that one of the gang got short of cash and went over to Poole and gave information for which he received 50 [a very large sum of money in those days]. The next day Mr. Lander, the chief Customs House officer, came to Swanage and called at Mr. Nat. Chichen's, at the Old Bank. Mr. Chinchen asked him to stay for lunch, but he said that he could not stop, as he had information that there was a large quantity of tubs packed away in Langton Church, and he must go and take charge of them at once. This he did and took them all away next day. I do not think that Langton Church was ever used for smuggling after that. [Mr. Hardy then discusses the rebuilding of Langton Church in 1892 on poor foundations].

[for more background information about Dorset smuggling procedures see: Smuggling in and Around Burton Bradstock.]

[Additional note re Chinchens - website:
Any chinchens in dorset/langton matravers?. Am looking to hear from anybody with information on Chinchen. Especially info on William Chinchen who age 9 (around 1846), was washed into the sea by a freak wave, while fishing with his friend off Dancing Ledge, and was sadly drowned. He had a younger brother John Albert Chinchen who was my paternal grandfathers uncle.]

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INTRODUCTION:

Access: Walk to Dancing Ledge of Jurassic Coast

An old topographic map of the coast west of Durlston Head and including Anvil Point and Dancing Ledge, near Swanage, Dorset

Dancing Ledge (SY 997768) can be reached by Durnford Drove, a lane south from Langton Matravers, parking and walking to Spyway Barn (SY 999777 - National Trust with information), and going down the hill to the cliff.

(An alternative route is a longer, walk along the cliffs, 3 and a half kilometres from Durlston Castle (SY 035772) and Durlston Country Park (SY 032773), south of Swanage.)

To give more detail, first drive to Langton Matravers, which is an old quarrying village to the west of Swanage, Isle of Purbeck, east Dorset, southern England.



LOCATION AERIAL PHOTOGRAPH

(NOTE - AVOID CLICKING IF YOU DO NOT WANT TO MOVE OFF THE ORIGINAL WEBPAGE! If you click this goes off to separate webpage and does not automatically return! you have to return via your browser to Dancing Ledge web page.)




In Langton Matravers find Durnford Drove. This is a road turning off to the south from about the middle of the High Street in the village (you can make a mistake and take the wrong turning - look specifically for the road name sign "Durnford Drove"). Turn down this and drive on for a few hundred metres south to the end of the tarmac road (and a turning circle). Then go onward using the rough stone road for another few hundred metres until you come to a National Trust car park. Park on the grass and walk towards Spyway Barn, a farm up on the hill top. It is almost a straight route to the south.

A carving set in a drystone wall south of Spyway Barn near the path to Dancing Ledge, Jurassic Coast, near Swanage, Isle of Purbeck, Dorset

Walking down from Spyway Barn to Dancing Ledge, near Swanage, Isle of Purbeck, Dorset, Jurassic Coast, 2007

Beyond Spyway Barn you will find a National Trust footpath and steps down the steep hill side. At the bottom is a stile and a path in to the top of the quarry.

The western part of Dancing Ledge, Dorset, seen from the sea on 28 August 2007

You will now be on the path above the quarry. See where the people are near the fence, with some of them having a picnic.

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INTRODUCTION:

Arriving at Dancing Ledge, Jurassic Coast

A large-scale map of Dancing Ledge, near Swanage, Isle of Purbeck, Dorset, Jurassic Coast

A view over the old quarry of Dancing Ledge, near Swanage, Isle of Purbeck, Dorset, January 2010

A general view of the old quarry floor of Dancing Ledge, near Swanage, Isle of Purbeck, Dorset, looking eastward towards Green Point, 7th September 2007

From the viewpoint go down the steps into the old working floor of the Dancing Ledge Quarry. The wide quarry floor gives excellent views of the strata and of the sea. Most people go just to here, and walk and study around the old cliff quarry. Some scramble down to the lower ledge on which the sea breaks (see section on Lower Ledge below).

Routes down from the quarry ledge to the sea ledge at Dancing Ledge, near Swanage, Isle of Purbeck, Dorset, view from the sea, 2007

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INTRODUCTION:

Geological Maps etc.

Recommended for location and topographic information is the Ordnance Survey Outdoor Leisure Sheet 15, 1:25,000 - Purbeck and South Dorset. The Geological Map is the Swanage Sheet - 343 and Part of 342, obtainable from the British Geological Survey .

Geological map of the Swanage, Isle of Purbeck, area, based on an 1895 edition

Geological map of the coast at Winspit, Seacombe Cliff and Dancing Ledge, Dorset

Geological map showing the remarkable extent of erosion of Portland strata offshore from the south of the Isle of Purbeck, including Dancing Ledge, near Swanage, Isle of Purbeck, Dorset

The 2000 edition of the 1:50,000 British Geological Survey Map, Swanage, Sheet 343 and part of 342, Solid and Drift - including the Isle of Purbeck and Lulworth Cove

The British Geological Survey map, 1:50,000, Solid and Drift, 2000 Edition, Swanage Sheet, 343 and part of 342, is well-worth purchasing. It can be obtained from the British Geological Survey website and is very inexpensive, costing only 12 pounds sterling. The map shown above is the new edition of the year 2000. It is different in some respects from older editions. Much of the nomenclature is relatively new but if you already know the stratigraphical sequence in the old terminology, it is quite easy to translate to the new language. The new map shows new data offshore and this is not on the old editions; it also shows areas of quarried-out ground. It shows less faults and less dip data for this part of the coast. Thus, both old and new editions should be used for serious study of these cliffs.

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AERIAL PHOTOGRAPHS

Seacombe, Dancing Ledge, Blackers Hole and the Amphitheatres etc.

Aerial photograph, small-scale of the Dancing Ledge, Seacombe and Blackers Hole coast near Swanage, Isle of Purbeck, Dorset, courtesy of the Channel Coastal Observatory

Aerial photograph of Dancing Ledge, Isle of Purbeck, Dorset, courtesy of the Channel Coastal Observatory

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INTRODUCTION:

Stratigraphical Succession

Comparison of Portland Group successions in the Isle of Portland and the Isle of Purbeck, Dorset, old scheme after Arkell

This classic diagram, based on Arkell (1933) shows the general uppermost Jurassic/basal Cretaceous succession in the Isle of Purbeck , compared with that on the Isle of Purbeck. The Purbeck sequence follows. This classic sequence of clays and limestones has been described by Arkell (1933; 1947) and many other authors. Sedimentology has been discussed by Townson (1975), West (1975), Bosence (1987) and others. Note that there are correlation problems and arguments referred to in the section on Zones of the Portland Group, below.

Terminology of the Portland successions

Two alternative schemes for the terminology of the Portland and Purbeck successions are given here. Townson (1975) introduced a largely new terminology. However, it has not been widely used and the traditional scheme of Arkell, shown on the left is still in more common use (diagram after Bosence, 1987, from Townson, 1975). See Wimbledon (1986) for some discussion of this, and note also that some correlation problems which affect this are discussed in the section on zones, below.

The Portland Succession in East Isle of Purbeck, Dorset, shown in a simplified succession

Portland Stone Succession - lateral changes

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Cliff Section - St. Aldhelm's Head to Durlston Head

A view of the cliffs east of Dancing Ledge, near Swanage, Isle of Purbeck, Dorset, showing Blackers Hole, Connor Cove and Fisherman's Ledge, telephoto, 1st January 2013

A cliff section of the Portland Stone cliffs between St. Aldhelm' Head and Durlston Head, near Swanage, Isle of Purbeck, Dorset, including Dancing Ledge, Seacombe and Winspit

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LOCATION:

Upper Ledge, the Old Quarry of Dancing Ledge

Looking westwards down into the old Dancing Ledge Quarry, near Swanage, Isle of Purbeck, Dorset, photo 1999

Dancing Ledge from the path above

Dancing Ledge - view east

The eastern end of the upper ledge of Dancing Ledge, near Swanage, Isle of Purbeck, Dorset, 2010

Here are some views of parts of the abandoned Dancing Ledge Quarry. Some are from the coast path above, walking from the east. Others show parts of the upper and lower ledges

Notice in the central image the situation of the quarry at a small valley. The photographs show the two main levels at the quarry, a broad ledge near sea-level composed of a gently southeast dipping unit of the Portland Cherty Series, which will be discussed later, and and upper, intensively quarried ledge of Portland Freestone, seen here. This upper ledge or upper part of Dancing Ledge is almost entirely artificial and is the result of the large volume of quarrying, much of it to create Ramsgate sea and harbour wall ( Bruce, 1989). Some rubble is left but most of the stone has been removed, and there are no large stacks of waste stone as is common on the Isle of Portland.

Apart from the extensive open-cast quarrying there are also some galleries in the Under Freestone near the path down to the ledge.What were formerly quite large openings in this northwestern embayment of the quarry have been partly closed in leaving just the barred openings for bats which you can see as square black apertures. The cliff edge above has received a coating of some some black netting, presumably to reduce danger from falling rocks.

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STRATIGRAPHY:

Upper Ledge - Portland Freestone Succession

Part of the Portland Freestone succession in the back cliff of the upper ledge or abandoned quarry of Dancing Ledge, near Swanage, Isle of Purbeck, Dorset

The succession of Portland Freestone here is similar to that of Seacombe and Worth Quarry. The galleries are in the Under Freestone and Under Picking Cap. The House Cap is shelly and lies above the level of the galleries. The Chert Vein, Bed S, (with the Listy Bed) is easily seen. Above that is the Pond Freestone, not of easy access here and then comes the Titanites Bed which is shelly. The top of the Portland Freestone succession is formed by the white and splintery Shrimp Bed. Thin bedded clays and limestone of the basal Purbeck Formation complete the sequence in the cliffs. These Purbeck strata are most thickly developed at the eastern end of the cliff above the upper ledge. They are not easily accessible here but there are fallen blocks of stromatolitic (thrombolitic) limestone in the quarry debris.

Titanites impression

Here is a rather poor impression of a Titanites ammonite, in a block lying loose in the western extension of the upper quarry. It may be from the Titanites Bed. This giant ammonite is of Perisphinctid type and it is surprising that such large cephalopods apparently lived in the relatively shallow waters of the Portland Stone sea. A good place to see better examples of Portland ammonites is at the Portland Heights Hotel, Isle of Portland .

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LOCATION:

Upper Ledge - Back Cliffs with Basal Purbecks

The petrographic lithology of the basal Purbeck Formation in Dorset shown in a series of graphic logs

Purbeck thrombolites (stromatolites) above the Portland Freestone in the back cliff of Dancing Ledge, near Swanage, Isle of Purbeck, Dorset

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LOCATION:

Upper Ledge - Small Cave, of Karstic Origin

The location of the small cave in the north face of the Dancing Ledge quarry, near Swanage, Isle of Purbeck, Dorset, Jurassic Coast

The small pothole in the north side of the Dancing Ledge quarry, near Swanage, Isle of Purbeck, Dorset, as seen on 17th September 2007

Dancing Ledge - natural cave

At the back (north side) of the upper quarried ledge of Dancing Ledge is this small natural cave. It is situated in an interesting place. It is now largely filled with rubble, but at one time was clear to about 1.5 m (in the 1950s). It is vertical and roughly circular in cross-section. Consider the origin of this and look at the signs of traverine around and above it. (The scale is Ian West in September, 1999).

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LOCATIONS:

Upper Ledge - Rock Samphire

Rock samphire at Dancing Ledge

Shown for general natural history interest is this rock samphire, Crithmum maritimum, above a sea cave at the extreme western end of the Dancing Ledge - upper ledge. It is very common on these cliffs and is shown here in September (1999). It is a greyish hairless perennial with fleshy lobes and yellow flowers.

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LOCATION:

Upper Ledge - The Stone Quarrying

Old galleries of the quarrying in the nothern part of the Dancing Ledge Quarry, near Swanage, are now walled up and only bats now have access, through the gaps in a steel grill

The quarrying of the upper ledge, the main part of Dancing Ledge was partly opencast and partly in horizontal mines or galleries. Some of these near the far western end are almost closed now by fallen debris. Those in the northern re-entrant have been artificially blocked in recent years and have a grill for the entry and exit of bats. Years ago all these galleries were open and accessible to humans and I often used to go in them and look at the bivalves in the roof. Presumably bats are exempt from modern health and safety regulations.

Quarrymen at an Isle of Purbeck cliff quarry in the Portland Stone, near Swanage, Isle of Purbeck, Dorset

The quarrying on the cliffs at Dancing Ledge and other nearby coastal quarries was only possible because back in the 19th century it was economical to transport the stone by sea. Later, when it became much more common to transport stone by road, it was still not feasible to move the heavy stone up the hills of this coast, either using the old system of by horses or later by motorised road transport (Benfield, 1948). Quarrying then only continued at places where there was reasonable road access. Neither Dancing Ledge Quarry or Hedbury Quarry had this.

According to Stanier (1996) Dancing Ledge Quarry was worked in the open by James Webber and two or three men, but activity was at a standstill in 1893. The quarrying of the Portland Stone here in the cliffs was never easy. It seems to have been more difficult in some respects than the quarrying of Purbeck Stone, where relatively thin individual beds have shale or marl between. In addition there was a great overburden of stone that was then regarded as useless. As far as possible this had to be removed but to some extent adits or "caves" were cut into the wall of Portland Freestone. At Dancing Ledge most of these are now inaccessible and some have been closed off with rectangular grills and are preserved for the use of bats.

Very primitive cranes were used in the 19th century for lowering limestone blocks from the main quarry working floor to the lower ledge. The above illustration shows the type of simple crane, operated by a ships-wheel type of winch. These must have been difficult and dangerous to use. In the photograph below a well-known quarry owner of this region, Trev Haysom explains the process.

Trev Haysom, Purbeck quarrier and marbler, explains the former stone quarrying at Dancing Ledge, near Swanage, Isle of Purbeck, Dorset, 24th January 2010

Trev Haysom, the Marbler, points out how the stone was lowered and shows the relics of a crane-place. Just here we are above the western end of the Lower Ledge. This is is the site of the derrick shown in the 1909 photograph below.

Old cranes for loading stone onto barges at Hedbury Quarry in 1865 and Dancing Ledge Quarry in 1909, the Portland Stone cliffs west of Swanage, Isle of Purbeck, Dorset

The Dancing Ledge cliff quarry (and the Hedbury Cliff Quarry) has no road access and so stone was lowered into barges from wooden derricks. These cranes seem to have been situated above large caves or recesses so that the barges could approach in safety. See: Stanier (1996) and Legg (2006), pp. 134-135 for more photographs and information. In 1865 only relatively small block were being lowered at Hedbury Quarry. In 1909 the typical large rectangular stone blocks, of the type still common on the Isle of Portland, were being lower. Blocks numbered 250 and 251 can be seen, so it was large consignment progressively being exported in 1909.

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LOCATION:

Lower Ledge and Cherty Series - General

Enlarged view of Dancing Ledge, Jurassic Coast, near Swanage, Isle of Purbeck, Dorset, seen from a boat and showing some aspects of the Lower Ledge, 2007

Dancing Ledge from sea, September 1989, photography by Gareth Lloyd

Descending to the lower ledge at Dancing Ledge, near Swanage, Isle of Purbeck, Dorset, January 2010

OUGS members ascend a rock face from the Lower Ledge at Dancing Ledge, near Swanage, Isle of Purbeck, Dorset, 24th February 2010

The Portland Chert Member junction with the Portland Freestone Member seen in the full cliff from near the Bathing Pool, at Dancing Ledge, near Swanage, Isle of Purbeck, Dorset, Jurassic Coast, 2010

If it is comfortably within your personal agility limits, you can proceed further down to the Prickle Bed ledge near sea-level. In the past this was usually done by most visitors, including children, and used to require nothing but a short scramble down an easy, rather step-like, rock face. However, recent sea erosion has made it steeper and rather more difficult. Do not descend if you think that you might have any difficulty climbing back up again. You can, in fact, see most features from the quarry ledge, the higher ledge.

The lower, natural ledge of Dancing Ledge, near Swanage, Isle of Purbeck, Dorset, showing rutways made for horn carts pulled by men to transport stone blocks to waiting boats

Once the blocks of stone were lowered from the working ledge they had to be transported to boats tied up against the seaward side of the lower ledge. The photograph above shows rutways described by Stanier (1996). He explained that they were purposely cut as routes for horn carts with curved shafts that were pulled by workers to move stone from the sites of the top cranes to the loading crane for the waiting boat.

Undercutting by the sea has taken place on the lower ledge of Dancing Ledge, near Swanage, Isle of Purbeck, Dorset, photo 2010

In photographs shown here, the two main levels of Dancing Ledge can be seen. The lower ledge can be reached by carefully scrambling down some rock to the east, that is to the right of the cave in the centre of the picture. However, undercutting by the sea has now steepened the cliff (and produced a little overhang) and this is not as easy as it once was. The lower ledge has a very gentle slope controlled by the gentle dip towards the east.

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Lower Ledge - the Bathing Pool with the James Bond Connection.

Thomas Pellat, the headmaster of Durnford Preparatory School at Langton Matravers had the bathing pool blasted out of the rock. See Wikipedia - Durnford School. This records that "Strip and swim" was the morning ritual for the boys who had to jump into the pool at Dancing Ledge from 1898 (as supervised by headmaster Thomas Pellatt). Ian Fleming who wrote the James Bond novels attended this tough preparatory school and swam in the Dancing Ledge Bathing Pool. Incidently, the name Bond is that of the owners of the great estate in the Isle of Purbeck not far from here.

Alan Holiday taking a photograph above the Bathing Pool, Dancing Ledge, near Swanage, Isle of Purbeck, Dorset, 2010

The bathing pool, quarried into the lower ledge of Cherty Series at Dancing Ledge, near Swanage, Isle of Purbeck, Dorset

The bathing pool at Dancing Ledge, near Swanage, Isle of Purbeck, Dorset, as seen on the 24th January 2010

The Dancing Ledge Bathing Pool, near Swanage, Isle of Purbeck, Dorset, seen in about 1950, tinted image

The Bathing Pool at Dancing Ledge, near Swanage, Isle of Purbeck, Dorset in 1989

These photographs are of the eastern part of the lower ledge, reached by an easy scramble from the main quarried ledge above. The swimming pool in the lower ledge was made for use of the pupils and staff of Durnford Preparatory School on the orders of the Headmaster who once owned this land.

(Footnote: Trev Haysome, the well-known Purbeck quarry owner, geologist and historian, told me a little more about the swimming pool. The owner and Headmaster at one stage had the pool painted white. He fixed a large steel mesh cover on the pool to prevent the common people from using it. However, one day he partly rolled the metal mesh back landwards to swim in the Dancing Ledge pool himself. A large breaking wave came in from the sea throwing him hard onto the steel mesh. The impact made patterned scars into his skin which he thouth would remain to his dying day.)

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Lower Ledge - Origin

The origin of the lower ledge is a problem. It is unusual on this stretch of coast to see such such a large flat ledge. The first question that arises is whether it is entirely natural or whether it is some result of quarrying.

It seems to be mainly the result of sea erosion rather than of quarrying because the Cherty Series here was not really of much economic use, until recent times (it is used now on the Isle of Portland and crushed for aggregate). There is a puzzle, though, because there do not seem to be large ledges of this type elsewhere on this stretch of coast. Usually there are small ledges or large boulders of fallen debris. Perhaps it is here because the dipping Prickle Bed or Puffin Ledge intersects sea-level.

All the stone from these quarries used to go out to sea in stone-transporting boats. These were strong, inelegant, flat-bottomed craft of about 7m in length which were towed to the site by ketch-rigged sailing barges, and were small enough to get inshore under the gibbets or whims. They were pointed at both ends and were normally rowed by two men with sweeps, although they did have a lug sail for use when conditions suited the ferrying of stone out to anchored sailing barges under sail. Though they were built very strongly, with oak frames and one-inch planks, such craft loaded with about six tons of stone did sink from time to time, whereupon their crews had to cling firmly to their buoyant wooden sweeps ( Bruce, 1989).

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Lower Ledge:

The Prickle Bed or Puffin Ledge (Bed J')

Examine the photographs again. The lower ledge is formed by Bed J', the Prickle Bed or Puffin Ledge, a notable thin unit in the Portland Cherty Series. Arkell (1947) described this as follows: "The most conspicuous, easily recognised datum in the Cherty Series all along the cliffs. A comparitively soft chertless bed; weathering reveals a peculiar ropy structure reminiscent of lava and in places of pillow-lava; and a mass of ramifying forms probably due to algae [sic]. Behemoth [giant ammonites - probably a species of Titanites] at Seacombe and Winspit. "

Although they were once called "fucoidal" (like seaweed) in the old literature, the ramifying forms are not due to algae. Thay are Thalassinoides ichnofossils, the result of bioturbation by decapod crustaceans (crabs). Irregular cementation and compaction and perhaps some pressure solution has been involved in addition and accentuated the lumpy structure. Such features are typical of a carbonate sediment of very slow deposition, probably a hardground, of hiatus origin.

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LOCATION:

Lower Ledge and Cherty Series - Ammonites

Giant ammonites in the Prickle Bed at Dancing Ledge, near Swanage, Isle of Purbeck, Dorset, 2007

Giant ammonite in the Prickle Bed

Larg worn ammonites are quite abundant in the Prickle Bed (J') of the main lower ledge at Dancing Ledge. They are usually not sufficiently well-preserved to see the full detail of ribs and are generally not identifiable. This is the basal bed of the Galbanites (Kerberites) kerberus Zone and has been correlated with the Basal Shell Bed of the Isle of Portland ( Wimbledon and Cope, 1978). This zone which continues up to the top of the Cherty Series contains Galbanites (Galbanites) galbanus, Galbanites (Kerberites) kerberus and species of Titanites including Titanites titan and Titanites giganteus. Thus, although this is the kerberus Zone, it would be wrong to think that there are no Titanites and that they only occur in the overlying Titanites anguiformis zone. Titanites anguiformis is larger and more finely ribbed than the other species of the genus and thus, according to Wimbledon and Cope (1978) is easily recognisable in the field.

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LOCATION:

Lower Ledge and Cherty Series
Sea Caves of Western Dancing Ledge

The western end of the lower ledge of Dancing Ledge, near Swanage, Isle of Purbeck, Dorset, with major sea-cave development, January 2010

Further west from the western end of the lower ledge, Dancing Ledge, near Swanage, Isle of Purbeck, Dorset, 24th January 2010

Large sea caves at the western end of the lower ledge of Dancing Ledge, near Swanage, Isle of Purbeck, Dorset, 2010

The succession of the Portland Cherty Series, Dancing Ledge Member, Dancing Ledge, near Swanage, Isle of Purbeck, Dorset, with a tombstoner for scale

View into the first cave to the west of the lower ledge of Dancing Ledge, near Swanage, Isle of Purbeck, Dorset, 2010

At the western end of the lower ledge there are sea caves. There is also a good view through a fairly long sequence through the upper part of the Portland Cherty Series succession. The scale is provided by a "tombstoner" (this is an unwise and dangerous activity because there are submerged rocks). The photograph has the main units of the upper Cherty Series listed. The most conspicuous bed is the Prickle Bed or Puffin Ledge, J', mentioned above. Here it is several metres above sea level so that underlying cherty limestones have been broken out by the sea and the ledge has collapsed. Other units of the Cherty Series can be seen here. The uppermost Cherty Series, beds M and N form the roof to the cave.

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LOCATION:

Lower Ledge and Cherty Series

The Chert and Its Origin

A close view of chert in Bed K of the Portland Chert Member, Portland Stone Formation, Dancing Ledge, near Swanage, Isle of Purbeck, Dorset, 2010

Chert in the Cherty Series

In these photographs the Portland chert is shown more closely. It is easily seen in the back cliffs of the lower ledge, near the Bathing Pool. Above the Prickle Bed, J', which forms the main lower ledge, the cherty limestone is accessible in the low cliffs up to the upper and quarried ledge of Dancing Ledge.

Serpulitic Chert in the Cherty Series

The serpulitic chert shown above is in the Chief Serpulite, bed L. The serpulids, Glomerula gordialis, preserved in the chert, as are other fossils, show that it is replacive. Note that the chert looks much like the black flint in the Chalk but is rather coarser-grained and fractures in a more angular and less conchoidal manner. Like flint it is, of course, harder than steel; do not hammer it because it gives dangerous sharp splinters at high velocity and this can cause injury, even blindness.

Chert, of course, consists of silica in the form of chalcedony. It was probably originally opal but has undergone some crystallisation processes over the millions of years. It developed as nodules quite soon, in geological terms, after deposition of the lime sand, probably within about 5 to 10 million years (and perhaps much less). The evidence comes from the occurrence of Portland chert reworked into the Upper Purbeck Formation at Friar Waddon near Weymouth (West and Hooper, 1969). The Wealden sediments of the Lulworth area also contain detrital Portland chert.

The source of the silica was the abundance of small, reniform and opaline sponge spicules present in the limestones of the Cherty Series. The silica of these Rhaxella spicules has been replaced by calcite and the silica has migrated in solution to be precipitated as the replacive nodules. The main controlling factor was almost certainly pH. At high pH values, over about 9.4 (i.e. in alkaline conditions), silica is very soluble. Such high pH values are obtainable in water in contact with calcite (i.e. limestone) provided that the pCO2 (i.e. the content of dissolved carbon dioxide in the water) is very low. Thus the opal of the sponge spicules can dissolve and at any local centre with a slightly lower pH, such as where, for example, some organic matter is decomposing to produce carbon dioxide, there silica can be reprecipitated. Obviously, the details are more complicated and a factor of importance is that precipitation of a mineral on existing nuclei requires less energy than precipitation anew. Thus once nodules start to form they continue to grow as silica is preferentially deposited on them.

Just when the main change from opal to chalcedony took place is not known. It was obviously, in general, pre-Tertiary tectonism. Some chert formed at the time of this late tectonism, and this late chert can be seen at Dungy Head, St. Aldhelm's Head and other places. Obviously it implies that some opaline silica was still present within the rock and that the pH of co-existing brine was high, but the details are not understood. Late preservation of opaline silica is not remarkable because there is still some opaline silica present in the Chalk even now. There might still be some opaline silica existing in the Portland Stone Formation. The high pH of the tectonic brines is interesting.

Burial temperature and time are probably the main factors (thus rocks with chalcedony are more likely to have been associated with oil source rocks that rocks with opal). In general opal persists (with some chalcedony) in strata of Cenozoic age. In Mesozoic strata the usual form of silica in nodules is chalcedony (of the varieties quartzine, lutecite and chalcedony sensu stricto). Because it is isotropic under the polarising microscope opal is not easily seen. It is, however, present in the Chalk as shown long ago by Judd, although it is normally not seen (it can be found by dissolving chalk in acid). It is not known whether any persists in the Portland Group.

In the field most of the Portland sponge spicules, the Rhaxella spicules are invisible. The branched spiny spicules of Pachastrella can be seen though. A good place to look is at the top of the Cherty Series in bed N at the seaward margin of the upper ledge (the quarried ledge) of Dancing Ledge. Look for white silicified calcarenite (like oolite) and examine a surface carefully with a hand-lens. Under a microscope the tubular structure of the now chalcedonic spines with a central canal is clearly seen. Arkell (1947) refers to an abundance of Pachastrella in "silicified oolite"[silicified calcarenite] at St. Aldhelm's Head.

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LOCATION:

Green Point, East of Dancing Ledge

East of Dancing Ledge from sea, 1997, photograph by Dr. Clive Boulter

Green Point, close view, 1997

The eastern end of Dancing Ledge and Green Point where a major faults displaces the Portland Stone

East of Dancing Ledge at Green Point a major extensional (i.e. normal) fault, probably of Late Kimmerian (Cimmerian) or Intra-Cretaceous age, displaces the Portland Stone. It has a throw of about 80 ft. or 24 metres, and this is the largest fault in the cliffs between St. Aldhelm's Head and Durlston Head. The fault upthrows on the east side. At this point part of the cliff is green with algae from water which runs over the top just here. There has also been some precipitation of travertine. The truncated valleys and the sea-cave features here are also of interest.

Notice the large fallen rocks to the right (east) of the Green Point Fault. The Portland Sand is above sea level, at the foot of the cliff here, and the fallen blocks are lying on this. It is common for Portland Sand outcrops in these cliffs to have such large fallen blocks of Portland Stone lying on them (cf. the Ragged Rocks).

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LOCATION:

Green Point Waterfall - Runoff and Perched Aquifer

View eastward towards Green Point from the lower ledge of Dancing Ledge, near Swanage, Isle of Purbeck, Dorset, 24th January 2010

The cliffs of Portland Stone and Purbeck strata at Green Point, near Dancing Ledge, Isle of Purbeck, Dorset, labelled to show the Green Point Fault and other geological features

The waterfall at Green Point, east of Dancing Ledge, near Swanage, Isle of Purbeck, Dorset, January 2010

Diagram explaining the seepage from a perched aquifer at Green Point, near Dancing Ledge, Isle of Purbeck, Dorset

The Green Point Fault is the largest north-south, extensional fault between St. Aldhelm's Head and Durlston Head. It has a throw of 24 metres and is a normal fault with multiple fault planes and some fault drag. It extends several kilometres offshore to the south as shown on a geological map given above. It is one of many such extensional faults in the south Isle of Purbeck cliffs, including those of Kimmeridge. The age is not proven and their origin is still debatable. They could be sigma 3 responses to the south-north compression of the "Alpine" orogeny that formed the Purbeck faulted monocline. It might seem simpler to explain them as direct extensional results of the general Late Kimmerian (or Intra-Cretaceous or Sub-Albian) tectonics, but this may not have been confirmed as yet.

Ehe Green Point Fault has produced an interesting little example of both runoff and a perched water table, controlled by the location of the fault. This occurs on the downthrow (western) side and produces a small waterfall with green algae in the lower part. This is the origin of the name "Green Point".

A small stream seems to have shown uniclinal shift in a downdip direction, but has been limited by the fault plane (and Portland Stone outcrop on the upthrow side). Thus the small and ephemeral stream is located just west of the fault.

An additional factor is a small perched aquifer. The uppermost part of the Portland Stone in the area is the Shrimp Bed. This pelmicrite is quite well-cemented, and, although much fractured, it is probably of low porosity and permeability. It may act as an imperfect aquiclude.

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BASAL PURBECK STRATA

General and Aquiclude Effect

Following the above discussion of aquicludes, it should be noted that there are thin are some thin carbonaceous clays (equivalent of the Lower Dirt Bed). These are too thin to be good aquicludes but undoubtedly hold up some water.

Above the partial aquicludes is calcitised anhydrite of high porosity and permeability. Above that is a limestone breccia, the Purbeck Broken Beds. It has probably been further disturbed by solifluction and cryoturbation during the late Pleistocene. Because of this the separation of the Broken Beds from solifluction debris is not easy on these hazardous cliff tops. On the current BGS geological map much of this Purbeck breccia is shown as "landslip".

The Broken Beds are tectonically brecciated evaporites, largely calcitised and subjected to dissolution by groundwater. The gypsum or anhydrite has been lost in solution leaving a porous limestone breccia. Such residual evaporite breccias are known in the Alps and Pyrenees cargneules. Those are usually reddish and dolomitic because they are often of Triassic origin. The lateral equivalent of the Purbeck cargneule consists of anhydrite. This has been found in boreholes, such as the Arreton Borehole on the Isle of Wight, and the calcium sulphate is commercially worked as gypsum in Sussex (Mountfield Mine). See the old papers of West for more on this topic.

Details of the basal Purbeck strata at the eastern end of Dancing Ledge, near Swanage, Isle of Purbeck, Dorset, showing a potential perched aquifer and feeder for the Green Point seepage

The calcitised and brecciated Purbeck strata are very porous and permeable in the near-surface region. A dipping block of this is visible in the eastern part of the Dancing Ledge quarry. Water runs into this and seeps out at the fault, as shown in the diagram above. At some time in the past the water table in the cargneule or evaporite breccia has been higher and somewhere near its western limit there has been downward seepage and the development of a vertical cave or pothole (vadose). Other solution caves are likely to be present in this area, but as far as I know speleologists have not reported any. Several caves occur on the Isle of Portland.

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BASAL PURBECK STRATA - continued

Thrombolites at Dancing Ledge
(not "stromatolites" because not laminated)

A bed of thrombolites, showing in section, pinch and swell features, in the basal Purbeck Hard Cap, Dancing Ledge quarry, Jurassic Coast near Swanage, Isle of Purbeck, Dorset, 17th September 2007

A close view of two thrombolites in the basal Purbeck of the Dancing Ledge quarry, near Swanage, Isle of Purbeck, Dorset, Jurassic Coast, 2007

At the base of the Purbeck Formation, above the Transition Bed and a thin clay, the equivalent of the Basal Dirt Bed, there is the lowest bed of thrombolites. These thrombolites have been wrongly referred to in the past as "stromatolites" but actually they are not laminated. The thrombolites are of low relief. They are distinctive because they pinch and swell in section, which other strata do not. Some fallen examples can be seen amongst the old quarry debris in the central part of the upper, quarried ledge. No tree remains have been found within them anywhere so far, in the cliffs of the Isle of Purbeck, unlike Portland and the Lulworth area.

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LOCATIONS:

Further East of Dancing Ledge

Blackers Hole cave east of Dancing Ledge, near Swanage, Isle of Purbeck, Dorset, 28 Aug 2007, seen in the distance to the northeast

The fault at Green Point brings up the top of the Portland Sand to the east. The hard dolomite beds (the Black Dolomites or "Black Sandstone" of Arkell) are at the base of the cliff and support fallen blocks of Portland Stone. The cliff here shows a complete succession of Portland strata, with the full Cherty Series (Dungy Head Member and Dancing Ledge Member) overlain by the Portland Freestone (Winspit Member).

For Blacker's Hole please go to the:
Anvil Point to Blacker's Hole Webpage.

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LOCATIONS:

Leaving Dancing Ledge and Walking to Hedbury Quarry, Further West

Leaving Dancing Ledge, near Swanage, Isle of Purbeck, Dorset, Jurassic Coast, and walking to Hedbury Quarry, further west

Leaving Dancing Ledge Quarry there is an easy coastal path that takes you a short distance to another cliff quarry. This is Hedbury Quarry, less well-known than Dancing Ledge, and without access to the sea.

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LOCATIONS:

Hedbury Quarry, West of Dancing Ledge (SY 993768)

Aerial photograph of Hedbury Quarries, west of Dancing Ledge, Isle of Purbeck, Dorset, courtesy of the Channel Coastal Observatory

Hedbury Quarry, west of Dancing Ledge, near Swanage, Isle of Purbeck, Dorset, photo 17th September 2007

Portland Freestone and basal Purbeck evaporitic strata in the east cliff of Hedbury Quarry near Dancing Ledge, Isle of Purbeck, Dorset, 2007

Hedbury Quarry is another old cliff quarry about half a kilometre west of Dancing Ledge. Unlike Dancing Ledge there is no easy access to the lower part of the cliff. The quarry is in Portland Freestone and has several galleries in the particular bed, the Under Freestone.

The old cannon in Hedbury Quarry, west of Dancing Ledge, near Swanage, Isle of Purbeck, Dorset, as seen in about 1953 by Ian West and his mother

The Hedbury Quarry working floor with the cannon now mounted on a plinth, west of Dancing Ledge, near Swanage, Isle of Purbeck, Dorset, September 2007

Back in 1953 I encountered the old cannon there, lying loose in the stone rubble at that time. It has since been mounted in a stone structure. It is not known whether it is from a defensive battery or from the wreck of the Halsewell, not far away. According to Stanier (1996) it is said to date from 1903. The cannon is now mounted on a plinth as shown in the lower (2007) of the two photographs above.

This quarry provides quite a good section of the basal Purbeck strata. Although this part of the section is inaccessible, being high in the cliff, it can be interpreted, in general terms, by comparison with other sections in the neighbourhood. The lower part of the Hard Cap (Top Cap of Portland) with stromatolites (thrombolites) is overlain by calcitised laminated anhydrite, probably of the upper Hard Cap (and roughly equivalent to the laminated and evaporitic Bacon Tier of the Isle of Portland). Above from about the level of the Soft Cap upwards there is rather soft, porous calcitised anhydrite (probably originally after gypsum). The Broken Beds are in this facies and show some typical evaporite-type contortions. Limestone breccia is not well-developed. Above the equivalent of the Broken Beds the base of the Cypris Freestone Member is visible. The general Purbeck sequence is like that at Fishermans Ledge (Conner Cove) and just north of Durlston Head.

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MISCELLANEOUS:

Seal off Dancing Ledge

A seal with a fish just off Dancing Ledge, near Swanage, Isle of Purbeck, Dorset, 24th January 2009

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Acknowledgements

I would like to thank Ruth Brown, who has prepared an undergraduate project on the geomorphology of this area, for useful discussion in the field and assistance with the photography. I am very grateful both to Dr Clive Boulter and to Mr Gareth Lloyd for the use of photographs of the coast taken from the paddle steamer Waverley in 1997 and 1989 respectively. I enjoyed an opportunity to photograph the cliffs from the sea with a Bure Probus group from Mudeford in 2007. I am much obliged to Sheila Alderman for arranging an OUGS visit to Dancing Ledge in January 2010. I thank George Raggett for helpful photography from the lower ledge. Trev Haysom, the quarry owner and expert on the quarries of Isle of Purbeck kindly provided much information on the history of the Dancing Ledge quarry.

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REFERENCES AND BIBLIOGRAPHY

Please go to Bibliography for St Aldhelm's Head to Anvil Point

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|Home and Contents

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GO TO SOME OTHER LOCALITIES, NEARBY AND/OR OF PORTLAND STONE?

St. Aldhelm's Head
Winspit and Seacombe and adjacent cliffs, Isle of Purbeck
Anvil Point to Blackers Hole, Isle of Purbeck
St. Aldhelm's Head to Anvil Point - Geological Bibliography
Chapman's Pool, Houns-tout and Egmont Bight, Kimmeridge Clay and Portland Sand.
Isle of Portland - Geological Introduction.

Copyright © 2013 Ian West, Catherine West, Tonya West 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 non-commercial 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 cancel 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, Hampshire, kindly supported of the School of Ocean and Earth Science, National Oceanography Centre, Southampton (NOCS), and web-hosted by courtesy of iSolutions of Southampton University. The website is an unfunded, private activity, and does not necessarily represent the views of the School of Ocean and Earth Science, or National Oceanography Centre, Southampton or Southampton University.
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