OTX THE GEOLOGY OP THE SOUTHERN" WEALDEX AEEA. 



637 



44. On the Supeeficial Geology of the Sotjtheen Poetion of the 

 Wealden Aeea. By J. Vincent Elsden, Esq., B.Sc. Lond., 

 F.C.S. (Bead June 23, 1887.) 



[Communicated by the President.] 



Inteodtjctoey. 



Moee than thirty years have elapsed since Sir Roderick Murchison 

 published his well-known paper " On the Distribution of the Flint 

 Drift of the S.E. of England on the Elanks of the Weald and over 

 the Surface of the North and South Downs " *. The observations 

 contained in that paper are stated by the author to be far from com- 

 plete, and offered chiefly to elicit further inquiry and discussion. 

 Since that time the 6-inch Ordnance maps of this area have been 

 completed, and the superficial deposits of a considerable portion of 

 the district mapped by the Geological Survey. ]STo detailed descrip- 

 tion, however, of the nature and extent of the various drift-gravels 

 of the southern portion of the Wealden area has been published 

 since the completion of the accurately contoured maps of the 

 Ordnance Survey. Apart from the importance attaching to any 

 new investigations relating to the question of "Wealden denudation, 

 the superficial deposits of the area under consideration are of 

 interest on account of their extremely scanty occurrence, many of 

 the drift-beds to be hereafter described consisting of nothing more 

 than a thin coating of flinty loam, or of the mere fragmentary 

 remains of old beds of gravel. But in all cases the limits of these 

 beds are sharply defined, and their relation to the present contours 

 easily established. The following observations are offered as the 

 result of a somewhat detailed examination of a considerable part of 

 this area during the year 1886, but the investigation has of neces- 

 sity been limited to the district lying between the central dome and 

 the chalk escarpment of the South Downs. 



It will be convenient in the treatment of the subject to consider 

 each river-basin separately. 



The Arun Basin. — In the higher parts of the Aran- valley it has 

 already been shown that the bills are capped by patches of angular 

 chert, containing no flint, and representing probably the remains of 

 the Lower Greensand escarpment when it reached further south 

 than nowf. Around Chiddingfold, Fisherlane, and Dunsfold 

 Green there occur frequently thin patches of loam with Greensand 

 pebbles, sometimes cemented into a conglomerate. This deposit 

 occurs indifferently on the hills and in the valleys. On approaching 

 Slinfold we find a good deal of true river-gravel on the Weald Clay, 

 containing flints, pebbles of Wealden sandstone, and Lower Green- 

 sand ironstone and chert. On the central nucleus of Hastings beds 

 itself flints occur at Amy's Mill, near Horsham, where Mr. Drew 

 obtained a single fragment of flint from the gravel %. I examined 



* Quart. Journ. Geol. Soc. vol. vii. p. 349. 



t Topley, ' Geology of the Weald,' p. 200. f Ibid, 



