414 



H. A. Baker — Loose Arenaceous Sediments. 



than those at corresponding horizons anywhere to the west and for 

 many miles eastward. The Lower Thanet Beds of East Kent are, 

 however, finer than the finest sediments of the West Kent sequence. 

 Some of the very fine, indurated, muddy sediments of Pegwell Bay 

 proved so refractory in the laboratory that no mechanical analysis 

 was possible. The West Kent type of Thanet Beds shows the 

 greatest amount of variation in mechanical constitution seen in 

 these beds anywhere in the London Basin, the Equivalent Grade 

 factor ranging from "059 mm. at the base of the deposit to '\i% mm. 

 at the top. The evidence suggests that early in Thanetian times 

 special conditions obtained in the West Kent area, whereby loamy 

 and silty beds, not possessing in any marked degree the 



B-'''y.c<a^<;if7i,<i-^<?-7t^ 



'f^Cci.f*L.^C-<L^ 



Gi-a.4^ J\e,rU, 



&€L^tcrCiyfU 



/ 



/ 



/ 



Fig. 4. — Diagram showing thickness of Thanet Beds and range in mechanical 

 constitution, for various localities, from west to east, along the southern 

 side of the London Basin. 



characteristics of marine sediments, were being deposited locally, 

 somewhat before the definite establishment of typical marine 

 conditions. From the fact that the lower Thanet Beds eastward 

 and westward of West Kent (excluding the East Kent area) are 

 fairly well-sorted sediments, giving elutriation-curves of marine 

 type, one is tempted to hazard the conjecture that the lowest beds 

 in West Kent may be older than these. 



Thickness of deposit, together with narrow range of variation in 

 mechanical constitution, may be taken to indicate approximate 

 uniformity of conditions of sedimentation, and comparative paucity 

 of sediment with considerable lithological variation, the reverse. 



