DRIFTS OF FLAMBOROUOn HEAD. 417 



scntcd, aiul prove, I think, that tlio marine deposits torn up by the 

 littsenient-Chiy ice rested n])on a })latform of kSecondaries and not 

 upon older Glacial beds. Neither transported Secondaries nor shelly 

 masses of sea-bottora have yet been observed in any of the higher 

 lioulder-clays, a fact which seems to show that when these deposits 

 were once hidden under the Basement C'lay they were practically 

 rendered inaccessible to the ice of the later glaciation. 



1 therefore concur in the later results of S. V. Wood * with respect 

 to the Basement Clay, and regard it as the product of the earlier 

 ("Major'') glaciation, and roughly equivalent to the Cromer Till. 

 One of the chief difficulties in the classification and correlation of 

 the drifts of the North of England disappears if this view be correct. 



That the Laminated Clay should, in its northward extension, 

 partly pass into the Basement Clay (PI. XIII. fig. 3) shows that the 

 upper boundary of the Basement Clay is not so well defined as was at 

 one time believed. The stratified bed seems indeed to form a pas- 

 sage from the Basement to the lower part of the Purple Clay, and is 

 evidently no testimony for anything more than local conditions. 

 And this new evidence causes me to think that it may perhaps be 

 advisable, for the sake of convenience, to extend the upper limit of 

 the Basement Clay in the Holderness coast-sections so as to include 

 within it the band overlying the shelly clay, as seems indeed to 

 have been done by Wood and Home f. 



4. The Intermediate Series and Purj^le Boulder-clay. — The origin 

 and correlation of the beds between the U])per and Lower Boulder- 

 •clays on Plamborough Head constitute at once the most difficult 

 and the most important of the problems of the sections. 



I have shown that the Lower Clay is on the whole the prolonga- 

 tion of the Basement Clay of the Holderness coast, and shall also 

 show that the Upper Clay is roughly equivalent to the capping 

 Boulder-clays (" Hessle Clay ") of that region. But the intervening 

 beds seem at first sight to have little in common. In the Holderness 

 sections, and even at Bridlington, we find, between these beds, bands 

 of '' Pur])le" Boulder-clay, sometimes showing distinctly stratified 

 zones and sometimes lenticular seams of sand and giavel, which 

 have, notwithstanding, as much right to be considered the product 

 of land-ice as cither of the other Boulder-clays %. But on Flam- 

 borough Head the beds betweeu the Upper and Lower Boulder-clays 

 consist, as the details of the sections have shown, of a complex 

 and ever-changing series, often confusedly arranged, of silt, sand, 

 gravel, and bands of Boulder-clay. This series sometimes seems to 

 pass gradually downwards into the Basement Clay, but more often 

 the junction is distinctly one of erosion. Its relation to the over- 

 lying Upper Clay is similarly variable, — one section revealing a 

 gradual passage, while another shows displacement and erosion 

 at the junction. 



* ' Tbe Newer Pliocene Period in England,' part ii., Quart. Journ. Geol. 

 Soc. vol. xxxviii. (1S82) p. G()8. 



t Quart. Journ. Geol. Soc vol. xxiv. (1S()8) p. 148. 

 X Geol. k5ur\ej Mem. ' Ilolderuess,' pp. 20-36. 



