140 Reports & Proceedings — Geological Society of London. 



(which crops out north and north-west of the Chilterns) after the 

 final breach of the Chiltern scarp, in the gaps of which the quartz- 

 bebbles are found in such abundance. If this be correct, it would 

 indicate not only that the materials of which the gravels are composed 

 came from the north, but also that the vast quantities of quartz- 

 pebbles which are found everywhere in the upper plateau-gravels 

 nearest to Little Heath are derived from the same source. 



Reasons are adduced in support of the contention that the loamy 

 sands and gravels are marine deposits laid down in a shallow sea ; 

 and that they cannot be of Glacial origin. 



The area over which the gravels have been found extends for over 

 a mile and a half south-east and north-west, by about half a mile 

 north-east and south-west. They thin out towards the north-west, 

 where they are only found in occasional outliers around which the 

 Glacial beds rest directly upon the Chalk. It is clear that there 

 must have been a considerable erosion of the pebble-beds before the 

 Glacial beds were deposited. 



As to the age of the loamy sands and gravels, the presence of the 

 pebbles of puddingstone proves that they cannot be Heading Beds, 

 and as they rest directly upon the Chalk the London Clay and 

 Heading Beds must have been denuded before their deposition. 

 They must be later than the Miocene movements, and are obviously 

 pre - Glacial. They are apparently of marine origin, and their 

 similarity to the high-plateau gravels farther south and to the beds 

 at Headley Heath, JNetley Heath, etc., suggests their contemporaneous 

 deposition with these gravels. They are probably, therefore, of 

 Pliocene age. 



(2) "Notes on the Correlation of the Deposits described in 

 Mr. C. J. Gilbert's paper with the High-level Gravels of the South 

 of England (or the London Basin)." By George Barrow, F.G.S., 

 M.I.M.M. 



The gravels described in the preceding paper belong to a series of 

 widespread deposits of which the harder constituents have usually 

 been derived from two areas only : one within the Chalk escarpment 

 (or local), the other beyond this escarpment, but within that of the 

 Lower Greensand (neighbouring). The local constituents are 

 Beading or other Tertiary pebbles, and flint ; the latter is small in 

 quantity where the gravels rest on Tertiary beds, but much increased 

 where on the Chalk. In addition, pebbles of sarsen are not 

 uncommon ; they have been wrongly identified as quartzite. The 

 pebbles to which the term "neighbouring" is applied consist of 

 white quartz and lydite, all small ; they have been proved to have 

 been derived from the Lower Greensand, and this identification is 

 corroborated by the fact that over considerable areas small fragments 

 of chert from the Lower Greensand are associated with them. 



"Far-travelled" stones, derived from, the Bunter, Carboniferous 

 Limestone, Bed Chalk, etc., are entirely absent from these deposits 

 as originally laid down. 



So long as they are composed mainly of small pebbles the gravels 

 keep at a nearly constant level over a very wide area, a little more 



