The best of Dorset in words and pictures

Natural gifts

Dennis Smale captures the essence of the Isle of Purbeck

A map of the geology of the Isle of Purbeck, adapted from a map of 1884 by H W Bristow

From the Bronze Age to the Nuclear Age, the Isle of Purbeck, only seventeen miles across and nine miles deep, has given up its stone, clay, oil, and natural gas to be used all over the world. What is this island that stands at the eastern section of the Jurassic Coast with its new status as England’s first natural World Heritage Site? It is not an island in the true geographical sense, nor is its neighbour, the Isle of Portland. In fact, the Isle of Wight is the only true island of all three.

It is just some 70,000 years ago, during the last low sea-level, that all three were joined together in what geologists term the Solent river system. The rivers Frome, Stour, Avon, Test and Itchen were all tributaries of the river Solent within the Hampshire Basin. Only with the rising of sea-levels were they separated as we observe them today. The winding and graceful river Frome isolates one-third of the Isle of Purbeck from the mainland. The relentless sea washes and weathers away the other two-thirds of its coastline.

The true interpretation of the name ‘Purbeck’ is an enigma. Documents preserved in the British Museum name ‘Purbicinga’ in 948 in the Shaftesbury Register. We must wait, however, until Richard II in 1387 for the current spelling. Variations appeared before and after.

In numerous documents the Isle is referred to as a Royal Warren or Royal Forest, exclusively a hunting area for the Crown. King John (1199-1216) adored the Isle of Purbeck and named Corfe as his favourite castle of his dominion during his short but turbulent reign. He also was the only Royal personage to have his effigy, which can be seen in Worcester Cathedral, carved out of his beloved Purbeck marble.

Outbursts of anguish fill the air from the so-called true natives or Purbeckians should the dreaded word ‘Purbecks’ appear in print or be uttered by some poor uninformed individual. It will be explained with lots of arm-waving that residents of Portland and the Isle of Wight do not reside in the Portlands or Wights, so therefore you do not and cannot live in the Purbecks – there is only one Isle of Purbeck. Ironically, the protesters are not completely correct themselves, for the word first appeared in print following the inaugural lecture of the Purbeck Society in 1852 by Rev. John H. Austen, MA, on his Guide to the Geology of the Isle of Purbeck. He used the word ‘Purbecks’ entirely to explain the different beds of stone recently unearthed in the complex strata of this area.

Ponies graze on Studland Heath, which is on the tertiary rocks to the north of Corfe Castle

The true culprit in the controversy over ‘the Purbecks’ may be the majestic Purbeck chalk hills or downs. There are no fewer than 23 of them, with such evocative names as Flowers Barrow, Challow Hill, Brenscombe, Ailwood Down and Creech Barrow. To the stranger approaching this part of Dorset, the Purbeck Hills – or ‘the Purbecks’ – are visible for miles from every direction.

As you take a journey from north to south across the Isle of Purbeck today, you may enter through its main gateway of Wareham or via the chain ferry at Shell Bay. Either way, you will travel over the tertiary rocks of gravels, sands and clays. Clay has been dug out here since even before the arrival of the Romans by the Celtic tribe of the Durotriges and continues to be mined to the present day. The ball clay of Dorset differs substantially from other common clays of Cornwall and Devon in having no igneous content, so it is the most plastic and therefore the most valuable of the English ball clays. Serious extraction began in the middle of the 18th century, when the three main landowners (the Pitt, Calcraft and Bankes families) were keen to explore a new revenue for their respective estates.

Clay-mining was very labour-intensive. Large pits were worked by men cutting or digging the clay into terraces. The best clay was mined by underground shafts and tunnels supported by pit props, which was extremely hazardous for the clay cutters and resulted in many fatalities. The marketable clay was removed by horse and trucks and later by steam locomotives to wharves or quays around Poole Harbour at Ridge, Middlebere, Ower or Goathorn, to be exported to many countries. Abandoned workings are to be found, complete with traces of old tram and rail sidings, with each ‘permanent way’ now returned to nature, right up to and below the chalk hills to the north of Corfe Castle. Today, open-cast extraction is the normal method preferred.

Moving southwards, Purbeck’s spine has to be the prominent chalk downs that run from the Foreland at Studland, with Old Harry Rock and the Pinnacles, through to Worbarrow Bay. The majestic white cliffs of Worbarrow Bay continue into Bindon Hill, which becomes the backcloth to the natural amphitheatre that is Lulworth Cove. This chalk limestone was deposited some 90 million years ago in a sub-tropical sea. It was the Alpine earth movements 60 million years later that created the uplift and folds of our landscape visible today.

An aerial view shows the chalk ‘spine’ of Purbeck curving from the F oreland in the top left of the picture to Worbarrow Bay, then on to Bindon Hill behind Lulworth Cove in the centre of the photograph. Durdle Door is at the bottom.

As we travel south across the floor of the Purbeck valley of the Wealden beds, we must pass two more sea-deposited strata, those of the greensand and the gault. Both are rich in fossils. The Wealden beds were laid down in freshwater lakes, rivers and swamps, prolific in fossil remains. The early manor houses, like Whitecliff, Godlingston and Barnston, can all be found in this lush and fertile area.

We now climb the limestone escarpment that extends from Peveril Point in the east through the village of Kingston and descends westwards from there to Worbarrow Tout. This region integrates itself into the rich and diverse Durlston formations, which were once shallow freshwater and brackish lagoons, inhabited by numerous dinosaurs and early mammals. The north-facing slope of this escarpment has been quarried from medieval times through to the modern open-cast excavations. The stone, once prepared, is used extensively in all architectural features. The most famous was the blue Purbeck marble. Quarried during the 12th to 14th centuries at Wilkswood, Downshay, Afflington and Blashenwell, it was worked primarily into pillars and pillarets for ecclesiastical buildings the length and breadth of the kingdom.

There were at that time 130 measurable beds (the name for layers or strata of rock) recorded in one section of Durdlestone Bay, now Durlston Bay. Why Durdlestone Bay? As at Durdle Door, this is where the Purbeck broken beds meet the Portland beds and there is geological evidence, confirmed in Hutchins’ great history of Dorset, that an ‘arched rock’ existed here originally, hence the Saxon name ‘Durdle’ (nose hole). This bay is enshrined in geological records as the first place in the world where air-breathing mammal fossils were discovered. Through the years new discoveries have sub-divided the strata, so over 300 beds have been recorded to date in Durlston Bay.

Looking west from Knowle Hill over the Wealden beds of the Purbeck valley, running from Steeple Church towards the left of the photograph down to Lutton and Tyneham

Next comes the Lulworth formation, which is made up of the adjacent coastal area from Durlston Head through to Emmetts Hill just above Chapmans Pool. The first in this series are the famous Portland Beds of marine deposits, coming from a turbulent sea containing large ammonites and bivalves. Immediately below the Portland Beds emerges the famous Kimmeridge Shale, formerly a deep, muddy sea rich in small ammonites and diverse marine life. Kimmeridge Shale has been mined, worked and exploited by mankind since time immemorial – from Roman amulets through to the first oil well sunk in the late 1930s, which in turn led to the largest onshore oilfield in Europe.

All walks of life are surprised to find that Purbeck’s geology is a live, continuing story, yet one which goes back into the Jurassic and Cretaceous time zone, 200 million to 65 million years ago. This was brought home to me when a sucessful open day was held for the general public in June this year by D & P Lovell Quarries Ltd of Langton Matravers. Over a thousand people attended on the Saturday alone, besides numerous trade visitors on the day before from quarries as far away as Yorkshire. The Thursday had been devoted to local schools. Some 130 pupils were entertained and educated by a full team of craftsmen, showing the old and obsolete methods of stone extraction and the splitting of blocks of freestone with wedges with names like ‘plugs’ and ‘feathers’, then the latest modern equipment – circular and frame saws, planers and guillotines with automatic feeders – and polishing methods with numerous abrasive pads. On site were two well-known sculptors who taught the children individually to carve their names or initials on pre-cut stone squares previously assembled; this was one of the highlights of their day. Our assembled collections of rare fossils were on display to the children and adults alike, while I gave timed talks guiding everyone through the numerous beds of stone that lie contorted within the Isle of Purbeck strata.

It is this stone and nature’s isolation that have created and preserved the idyllic scenery of the Isle of Purbeck, which has inspired artists of all disciplines, from the paintings of Turner to the novels and poems of Hardy.

The author in Durlston Bay with the Durlston beds clearly visible behind him running up the cliff

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