442 ME. J. V. ELSDEN ON THE [Aug. I909, 



26. On the Geology of the Neighbourhood of Seaford (Sussex). 

 By James Vincent Elsden, B.Sc, F.G.S. (Bead May 12th, 

 1909.) 



Contents. 



Page 



I. Introduction 442 



II. Stratigraphy 443 



III. Structural Features 451 



IV. Physiography 455 



I. Introduction. 



The following paper deals with that part of the South Downs which 

 adjoins the coast between Beachy Head and Newhaven. Its 

 primary object was to investigate the variations of the dip and 

 strike of the Chalk strata in that area, with the view of discovering 

 the interpretation of the sudden westerly dip of the Chalk at 

 Seaford Head. Incidentally, the geological features of the sur- 

 rounding country and their relation to the surface-contours are 

 discussed, and reasons are given for the view that the true eastern 

 extremity of the structural area known as the Hampshire Basin 

 lies within this district. With regard to previous literature on 

 this part of Sussex, the whole question is summed up by Mr. Jukes- 

 Browne in the following statement, published in 1904 : — 



' At Newhaven the beds are nearly horizontal, so there must be a quick 

 recovery from the steep inclination which they show in Seaford Head. 

 Whether they are re-curved or faulted we have no means of knowing.' x 



Previous knowledge of the Chalk stratigraphy of this particular 

 area is, in fact, limited to Dr. Bowe's detailed researches on the 

 cliff-section. 2 It should be stated, however, at the outset that, 

 without the assistance derived from Dr. Bowe's paper, it would not 

 have been possible to carry out this investigation ; for the results 

 depend entirely upon the zonal criteria established by him, and 

 their application to the practical work of mapping the inland 

 outcrops of the higher Chalk-zones exposed in the cliff-section of 

 Seaford Head. This method seemed to be the only way of arriving 

 at a solution of the problems hereafter to be discussed. For, 

 although the lithological characters of these zones are often fairly 

 well defined, they are not alone a sufficient guide for the purpose 

 of fixing boundary -lines in the field, and it is therefore necessary 

 to rely mainly upon direct palseontological evidence. 



The area in question is drained by the Ouse and the Cuckmere. 



1 ' The Cretaceous Eocks of Britain ' Mem. Geol. Surv. U.K. vol. iii (1904) 

 p. 39. 



2 ' The Zones of the White Chalk of the English Coast : Part I— Kent & 

 Sussex' Proc. Geol. Assoc, vol. xvi (1899-1900) pp. 289-368. 



