440 J. C. Mansel-P ley dell — Geology of Dorset. 



other marine shells. The uppermost band, which is a dark-blue 

 finely-laminated shale, in part Cypridiferous, with thin bands of Lime- 

 stone, made up of Gijrena, Ostrtea, etc., is at present covered over by 

 the debris from the beds above. 



At Worbarrow the formation is about 68 feet thick, comprising a 

 thin well-marked band of ironstone containing vegetable markings 

 and casts of marine shells, with beds of grey and whitish laminated 

 clay and bands of nodular ironstone. These ironstones contain casts 

 of marine shells ; also beds of light-coloured, sometimes pinkish, 

 sand, with much carbonaceous matter. 



The Punfield formation is exhibited at Brixton Bay, a little to the 

 west of Atherfield Point, at Compton Bay, and Sandown Bay in 

 the Isle of Wight. 



GrAULT, Chalk Maul, and Lower Chalk. — It is difficult distinctly 

 to recognize the sub-division of the lowest beds of this series ; only 

 on the eastern side of the county is it of any importance ; it accom- 

 panies the Chalk in its varied sinuations from Abbotsbury to Cors- 

 combe, and occupies the summits of the insulated hills above Lyme 

 Eegis, Lewesdon, and Pillesdon ; it reposes successively on the Lias 

 at Lyme, on the Inferior Oolite at Golden Cap and Shipton Gorge, 

 on the Forest Marble at the Knoll of Puncknoll, on the Oxford Clay 

 south of Abbotsbury, on the Kimmeridge Clay west of Osmington, 

 and on the Purbeck Beds east of Abbotsbury. Its valleys of denu- 

 dation are seen at Askerswell, Compton Valence, and Winterborne 

 Steepleton. The Gault and Chloritic series has its greatest super- 

 ficial development in the vicinity of Shaftesbury, and produces strata 

 of chert, beneath which lies a band of sandstone, of great economic 

 value, on account of its power to resist the decomposing action of 

 the atmosphere ; it is extensively used for building, the angles of the 

 worked blocks retaining their original sharpness for centuries, — the 

 marks of the chisel are as fresh now as when first cut. A narrow zone 

 flanks the base of the Chalk range from Ballard Down to Worbarrow, 

 a fault brings it to the surface at Mewps Bay, it forms the base of 

 the eastern side of Lulworth Cove, and dips beneath the sea at 

 Durdle Door. At Bat^s Corner it re-appears and forms the coast-line 

 to Eingstead Bay, where a fault throws it northward above Hol- 

 worth, and it follows the Kimmeridge Clay to Osmington, whence 

 it turns eastward to Chaldon, skirting the north side of the Ridgeway 

 fault from Poxwell to Bincombe. It occupies the heights above the 

 village of Abbotsbury, and, after passing Gorwell and Little Bredy, 

 it forms the base of the escarpment of the eastern side of the vale 

 of Bredy. 



It is not difficult to conjecture that these Lower Cretaceous Beds 

 were continuous and extended over a large area westward, previous 

 to the denudation which has so seriously affected this district. In 

 the neighbourhood of Longbredy they are much disturbed : after 

 encountering several lateral and vertical faults, it forms the base of 

 Eggardon Hill ; from Chilcombe it continues in a southerly direction 

 through West Compton and Wynford Eagle. It fringes the base of 

 two Chalk outliers, the major axis of the larger one taking a north- 



