348 



H. W. MONOKTON ON THE BAGSHOT 



21. 27*0 Bagshot Beds of the London Basin. By Horace W. 

 Monchton, Esq., E.G.S. (Bead April 25, 1883.) 



The opening of several new railways during the last few years 

 has greatly increased the opportunities for studying the geology of 

 the Bagshot district. The railway-cuttings, however, are rapidJy 

 becoming overgrown or obscured by fallen materials, and I think 

 that a description of some of the sections may interest the Society. 

 In compiling these notes I have been greatly assisted by Mr. Herries; 

 and the lists of fossils are from our joint collection. 



The Lower Bagshot beds, 100 to 150 feet thick, consist of yellow 

 and white siliceous and micaceous sand, without green grains, with 

 beds of greyish sandy clay, often laminated, and with more or less 

 distinct vegetable impressions. On the western borders of Bagshot 

 Heath the base of these beds is marked by 



(a) Coarse, often ferruginous sand, occasionally laminated with nearly white 



clay and sometimes with pieces of wood. 



(b) Irregular and extensive masses of rolled flint pebbles. 



(c) Dark-coloured stiff clay, named Ramsdell clay by the Geological Survey. 



The Upper and middle Bagshot Sands of Prof. Prestwich, consist 

 of a series of the very persistent and well-marked beds shown in the 

 following table : — 





bd 



*5 



2 (t^ 



q to 2. 

 • to ^ 



05 O 



bd 



a 



Cft) 

 01 



Cf 

 o 



o 



Yellow siliceous sands with great 

 numbers of casts of shells, often 

 well preserved. 



B. Yellow siliceous sands with a few 

 green grains and casts of shells, 

 few and ill preserved. Beds A 

 and B are 226 feet or more thick. 



C. Pebble bed, more or less regular and 

 of variable thickness, in a greenish 

 or ferruginous sand. 10 to 18 

 inches. 



D. Yellow and greenish sands with ferru- 

 ginous layers and light-coloured 

 foliated clays. 10 to 20 feet. 



E. Yery fine green sand, with subordi- 

 nate dark clay and lignite. Fossils 

 abundant. Average about 20 feet. 



Laminated clays, often black or liver- 

 coloured, with beds of impure green 

 sand, lignite, and plant-remains. 

 15 to 20 feet. 



Shells of Lower 

 Barton species 



Shells of 



Bracklesham 



species. 



