498 



PLEISTOCENE. 



striking contrast with the dales of the West Riding, where the hill-tops, 2300 feet 

 high, are distinctly glaciated.'- 



Near Middlesborough a laminated brickearth of Glacial age has been employed 

 at the Linthorpe pottery. 



In the neighbourhood of York the Boulder Clay rests on the Trias, and is 

 capped by Glacial gravels and brickearth. In the Boulder Clay itself there are 

 contorted bands of sand and laminated clay, as in the Contorted Drift of Norfolk.^ 

 A considerable amount of Boulder Clay extends along the Yorkshire coast, from 

 Flamborough northwards. The beds are in places capable of division into Upper 

 and Lower Boulder Clay and Middle Sands. The Lower Boulder Clay contains 

 many large boulders of Shap Granite, Carboniferous Limestone, etc. The Middle 

 Sands are shown in the cliffs of Robin Hood's Bay. Eskers have been observed 

 in some of the Yorkshire valleys.^ 



In the cliffs of Ilolderness the Glacial Beds are grouped as follows : — 



Hessle Clay. 



Hessle Gravel (of Mr. Wood), unfossiliferous. 

 Upper Purple Clay. 

 Lower Purple Clay. 



Kelsea Hill Gravel. 



Hessle Mammaliferous Gravel? 

 Basement Clay, 



With Bridlington Shell-bed. 



Our knowledge of these beds is mainly due to the observations of Mr. S. V. 

 Wood, jun., the Rev. J. L. Rome, Mr. G. W. Lamplugh, and Mr. C. Reid. 



Bridlington SIic!l-hed.—T]\e Basement Clay, originally described by Mr. S. V. 

 Wood, jun., is a dark green or bluish Boulder Clay, containing numerous erratic 

 Boulders and much Chalk. Its most marked characteristic, and one that dis- 

 tinguishes it from other Boulder Clays in the East of England, is the common 

 occurrence in it of transported masses of olive-grey sand and clay containing 

 MoUusca, often quite uninjured and with the valves united. These fossiliferous 

 beds have been considered to be in place, and they have been designated the 

 Bridlington Crag.* The shells were originally noticed by Sedgwick, and later on 

 by William Bean, John Phillips, and others ; their occurrence in the Glacial Drift 

 was first pointed out by Mr. Wood.^ Still more recently Mr. G. W. Lamplugh 

 has had opportunities of studying exposures of the shelly beds at Bridlington (or 

 Burlington) Quay, and he has proved that they are included in the Basement Clay, 

 and not in the Purple Clay, as stated by Mr. Wood.*^ The beds, however, are 

 only visible, in places, at low-tide. 



Similar shelly layers occur in the Basement Clay at Dimlington, where a seam 

 with perfect specimens of Nucula Cobboldiie was found by Sir Charles Lyell and 

 Prof. Hughes ; and broken shells are also found in the Clay itself. In the former 

 case, as with the Bridlington shell-bed, the shelly layers occur as Boulders ; and 

 Mr.'Pamplugh has given his reasons for concluding that the shells lived on an old 

 sandy sea-bottom, which was afterwards covered by a thick deposit of glacial 



1 Geol. of Eskdale, etc. (Geol. Survey), notes by C. Reid, and G. Barrow, p. 51. 



- J. E. Clark, Proc. Yorks Geol. and Polyt. Soc. 1881, vii 421 ; Rev. W. 

 Thorp, Ibid. iii. 244; C. F. Strangways, Geol. N.E. of York, etc. p. 29; 

 Strangways and G. Barrow, Geol. Whitby and Scarborough, p. 52 ; J. R. 

 Mortimer, P. Geol. Assoc, viii. 287. 



3 J. R. Dakyns, Q. J xxviii. 382 ; G. Mag. 1S79, p. 3S2. 



* C. Reid, Geol. Holderness, p. 8. 



s Ann. Phil. (2), xi. 339 ; Bean, Mag. Nat. Hist. viii. 355 ; Lyell, Ibid. (2), 

 iii. 313 ; Phillips, Geol. Yorkshire, Part i, ed. 3, p. 87 ; Sorby, Proc. Geol. and 

 Polyt. Soc. W. Riding, iii. 5S9 ; Wood, G. Mag. 1S64, p. 246. 



6 G. Mag. 187S, p. 509, 1879, p. 393. 1881, pp. 537, 543, 1882, p. 3S3 ; Proc. 

 Geol. and Polyt. Soc. W. Riding (2), vii. 383, viii. 27, 240 ; Q. J. xl. 312. 



