Cretaceous and Older Rocks in East Kent. 549 



here. The finer portion must have been dropped further on in its 

 course. Possessed of this corrasive power in East Kent, erosion of 

 the Mesozoic area of its bed must have been inevitable, but doubtless 

 the finer part of the eroded material was carried beyond the area. 

 Rarity of Mesozoic debris is therefore to be expected in the Wealden 

 of East Kent, and where Mesozoic fragments do occur they are 

 probably of large size and marked angularity. Comparison of the 

 details yielded by some of the borings suggests that the Mesozoics in 

 East Kent underwent erosion in early Wealden times, although it 

 must be borne in mind that allowance must be made for the general 

 pre-Cretaceous denudation of the area. For example, the sites of 

 the Tilmanstone shaft and the Barfreston boring both lie on the sub- 

 Cretaceous outcrop of the Oxfordian, and since Tilmanstone lies 

 a little to the north-east of Barfreston we should expect the thickness 

 of Oxfordian passed through to be rather less there. In actuality, 

 only 3 feet of Oxford Clay remain at Tilmanstone, whereas 102 feet 

 were passed through in the Barfreston bore. It would appear, then, 

 that the early Cretaceous strike-stream which traversed the outcrop 

 of the Oxford Clay in the neighbourhood of Tilmanstone was 

 responsible for a considerable amount of erosion. 



With continued submergence Weald Clay times approached, and 

 delta conditions, ushering in the marine invasion of the Lower 

 Greensand, began to prevail. The waters of the Wealden lake 

 encroached northward upon East Kent, the velocity of the streams 

 was checked, finer sediments began to be deposited in quantity, and 

 base-level conditions were realized. The spreading waters united 

 the streams into a single sheet. The evidence shows that the main 

 stream and its two subsequent branches had become united into 

 a single sheet of water before the commencement of Weald Clay 

 times. Higher ground, separating the two subsequent streams from 

 each other, appears to have existed in the neighbourhood of Fred- 

 ville, yet 28J feet of Hastings Beds occur here. To the north-east, 

 however, the velocity of the stream still remained such that 

 deposition had not yet commenced. Probably in this area the 

 stream was active in removing from the Palseozoic floor some of its 

 Bathonian covering. With the advent of Weald Clay times, how- 

 ever, deposition proceeded over the whole area under water, and the 

 surface so long exposed to denudation was finally buried. In the 

 neighbourhood of Deal a small area of Coal-measures remained 

 uncovered until Lower Greensand times, and at and near Stodmarsh 

 an area of Bathonian remained until Gault times. 



Note. — After the proofs of this paper had been sent to the Editor 

 additional information became available in consequence of the 

 publication of the Summary of Progress of the Geological Survey 

 for 1916 (Mem. Geol. Surv. 1917). Details concerning three 

 additional borings (J. Pringle, Appendix II), viz., at Bere Earm 

 (If- miles north-east of Dover), Elham (close to Elham Station), and 

 Eolkestone, are now to hand. The Bere Farm boring shows the 

 sub-Cretaceous surface there to be composed of Corallian Limestone, 

 as was expected, although the thickness of the Wealden (42 feet) is 



