Vol. 57«] LANDSLIPS IN BOULBER-CLAY NEAE SCAEBOROrGH. 293 



21. On some Landslips in BouLDEE-CLAr near Scarboeough. By 

 HoEACE WooLLASTON MoNCKTON, Esq., F.L.S., y.P.G.S. (Read 

 June oth, 1901.) 



In the valleys which have been cut through the tabular Howardian 

 Hills, and on the hills themselves, there is a great scarcity of deposits 

 of Drift, but along the Yorkshire coast we find a remarkable band 

 of Boulder-Clay with an average width of about 2 miles. The 

 consequence is, that whereas inland the solid rock (Corallian, 

 Oxfordian, etc.) is exposed from the top of the hills to the bottom 

 of the valleys, along the coast the old pre-Boulder-Clay surface of 

 the ground is obscured, and only the higher points of solid rock, 

 such, for instance, as Oliver's Mount, project through the Boulder- 

 Clay covering. 



The old surface-features of the ground have been to some extent 

 exposed by the action of the sea. Thus the old Coral lian-capped 

 hill upon which Scarborough Castle stands has been worn out of 

 the Boulder-Clay in process of denudation, and even now a capping 

 of that clay remains on its top. 



South of the castle there was in pre-Boulder-Clay times a deep 

 valley ; for the Drift has been penetrated to a depth of over 100 feet 

 below sea-level,^ and this valley has been to a certain extent re- 

 excavated by the stream which flows from the Mere. 



The south side of the valley was formed of sandstones belonging 

 to the Estuarine Series, which at High Wheatcroft are covered by 

 Cornbrash and Kellaway's Rock ; but beyond White Nab we come to 

 another old depression, which is cut through by the sea in Carnelian 

 Bay. The depression sinks very little below high-water mark, but 

 no doubt it may be the upper part of a vaUey running in a 

 westerly direction to join the old River Derwent. Even now the 

 stream rising so near the cliffs as Low Wheatcroft flows in a 

 westerly direction to the Hertford River. 



Carnelian Bay, which scarcely deserves the name of bay, 

 comprises the coast between White Nab on the north and Osgodby 

 Nab on the south. The Oolitic rocks (Scarborough Limestone and 

 Estuarine Series) form the lower half of the cliff at White Nab, 

 and the old pre-Drift surface slopes down towards the south, and 

 a little north of Osgodby Nab it sinks below sea-level. 



The present surface of the ground is, however, fairly uniform — 

 being, indeed, a flat with a slight inland slope, — and consequently 

 the Drift, a mere capping 6 feet thick at High Wheatcroft, thickens 

 till it forms half the cliff at White Nab, and the whole of the cliff 

 in the southern half of Carnelian Bay. From this flat a broken 

 ridge runs out in the middle of the Bay, and a spur also projects 

 towards Osgodby Nab. 



^ C. Fox-Strangways & G, Barrow ' Geology of the Country between Whitby 

 & Scarborough' Mem. Geol. Surv. (1882) p. 51. 



