164 



GEOLOGY OF THE ISLE OE WIGHT. 



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On the east side of the Newtown river it appears above the 

 Osborne Beds at the Brick Yard, but sinks when traced in a 

 south-easterly direction, and is lost beneath the marsh of Spur 

 LaKo, to reappear in the bed of the stream near Porchfield for a 

 quarter-o£-a-mile. Continuino; eastward along the coast, the 

 Limestone in the cliff gradually falls till il spreads out on the 

 shore, forming two ledges with an expanse of dark green marl 

 between. Near Thoine?s Wood the stone is lost, and does not 

 rise again for about a mile and a half. 



The section in the cliffs near Burnt Wood is of great interest, 

 for it is almost the only place in the Island where the Bem- 

 bridge Limestone contains perfectly preserved shells and not 



merely casts. It also shows a dis- 

 tinct line of erosion between the 

 Limestone and the overlying marine 

 base of the Bembridge Marls. {See 

 Fig. 55.) 



The bottom block of Limestone 

 (not seen in the cliff at this point, 

 t)ut exposed on the foreshore oppo- 

 site) calls for no remark. It is 

 merely a freshwater limestone of the 

 usual character, with casts of Linmcea. 

 Above it comes a mass of dark green 

 somewhat mottled marl, the upper 

 part of which is crowded with perfect 

 specimens of the minute Paludina 

 globuloides. On this lies the top 

 block of Limestone : a soft earthy 

 stone, easily cut when first dug out, 

 but hardening by exposure. This 

 stone is full of uninjured specimens 

 of TAmncen pyramidalis, L. mixta, 

 and Plaiiorhis ohtusus, but only for a 

 short distance. The preservation of 

 the shells here is due to the stone 

 being sealed up in a mass of im- 

 pervious clay. The upper surface of 

 the limestone is much broken up and 

 eroded, and in the cracks are found 

 marine shells, Panopcea (or Mya) 

 minor having the valves united. In 

 some places the erosion has cut en- 

 tirely through the upper block of the 

 Limestone, so that the base of the 

 Bembridge Marls rests directly on the 

 green marl whhPaludiim (jhhuloides. 

 In Thorness Bay the Limestone rises again, showing the same 

 three divisions. The bottom block forms Gurnard Ledge, and 



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