Vol. 50.] ON THE PURBECK BEDS OF TnE VALE OF WARDOTTR. 59 



V. The Upper Furbeck Group. 



As stated on p. 50, we take the thick bed of clay seen in the 

 quarry-cutting west of Dinton to be the base of the Upper Purbeck 

 group. We do so, more for the sake of convenience than for any 

 resemblance to beds elsewhere ; but the soft and purely siliceous sand 

 which overlies the clay is a conspicuous bed, capable of identification 

 if exposed at other localities. A slip in the southern bank of this 

 cutting in October 1890 showed the following section : — 



Feet. Inches 



Gravel 3 to 4 



Yellow sand, with seams of grey sandy clay from 4 inch to 4 



inches thick 1 fi 



Yellow and brown sand, in alternating layers (base not seen) 8 



Wet grey sand, passing down into silty clay 



Stiff grey clay at the base. 



We may, therefore, assume that there is at least 10 feet of the 

 sand in this cutting. 



East of the watercourse and cattle-creep there is another cutting 

 almost entirely grassed over, but its western end does not seem to 

 be in sand, as it would be if the south-easterly clip were continued ; 

 and moreover the first beds seen are dipping westward, so that we 

 suspect there is a line of fault between the two cuttings. 



A hard shelly limestone crops out in the bank at intervals, rising 

 eastward ; and at a point about 80 yards east of the watercourse 

 we made a narrow trench down the bank, finding the following 

 beds in the lower two -thirds of the slope : — 



Feet. Inches. 



' Beef (fibrous carbonate of lime) 3 



Brown sandy clay 4 



Soft, calcareous, shelly marl G 



Stiff blue clay ',» 



Sandy clay, with layers of ' beef ' 4 



Grey shaly clay 3 



Soft yellow marl, with crushed shells 8 



' Beef ' (1 inch) and brown sandy clay 4 



Hard shelly limestone, grey inside, weathering yellowish ; with 



Unio 6 



Buff-coloured or brownish nodular limestone, with Cyrena media 



and Paludina 3 



' Beef ' and sandy stone 4 



Yellow and grey sand, with a log of endogenous wood in place... 3 



7 (> 



The soft sand at the bottom we consider to be the same as that 

 seen at the top of the western cutting, and as the overlying beds 

 contain Cyrena, Paludina, and Unio, we are inclined to regard them 

 as the equivalents of the i7»io-beds of the Dorset series. If our 

 reading of these partially obscured sections be correct, the eastern 

 cutting traverses an anticlinal flexure, the western limb of which is 

 faulted against the beds seen in the other cutting. We assume, in 

 fact, that the strata are broken by two faults, each with a down- 

 throw to the east as shown in the section on the next page (fig. 3). 



