part 1] aATJLT and lower geeensand n"ear leighton. i2-j 



Poplars pit provides a useful indication of the persistence of the 

 peculiar Shenley conditions at the base of the Glault in a north- 

 easterly direction, and Claridge's pit, next to be described, shows 

 that they extended northwards also. The Gault at present exposed 

 in Poplars pit is too shallow and weathered to afford palseonto- 

 logical data ; but its lithological characters agree with those of the 

 beds in the same position at Nine Acre (figs. 7 & 8, p. 16) and Mile- 

 tree (tigs. 10 & 11, pp. 19 & 20). The iron-grit breccia, with its 

 associated gritty glauconitic stuff, is also similar in all its essentials, 

 and the patch of fossiliferous limestone links the breccia be^^ond 

 question with that of Shenley Hill. The isolated chunk of chert, 

 which I dug out of the gritty loam infilling a hollow immediately 

 below the breccia, is rudely cuboidal, with well-rounded angles, and 

 possesses all over a peculiarly smooth glossy greenish surface, with 

 perfectly fresh, dove-grey, translucent rock under it. The only 

 other pit in which I have found extraneous stones so large as this 

 is at Chamberlain Barn, below the ' Mammillatus beds' (p. 31). 

 Small bits of similar chert occur among the ' lydites ' of the 

 Sands ; and the rock is almost certainly the same as that found 

 rather plentifully in the gravelly Lower Grreensand at Potton and 

 other places. 1 



West of Double Arches pit, the ground rises steadily for 

 about 100 feet to a broad ridge which is due to a thick sheet of 

 Glacial drift, and contracts southwards, terminating as a spur in 

 Shenley Hill. The drift-sheet has been deeply trenched on both 

 sides by Late-Glacial erosion, and the ground falls westwards from 

 the ridge towards the valley of the Ouzel. On the west side most 

 of the pits have been opened on the lower slopes, where the Sands 

 are at the surface ; but in two or three cases they have been worked 

 back into the covering deposits, and these only will be described. 

 The northernmost is Claridge's pit, a big working a quarter of a 

 mile east of the high road between the villages of Heath and 

 Keach, and nearly a mile due west of Double Arches. 



Claridge's pit (fig. 15, p. 26) has broken into a sharp spur of 

 upland drift, and shows a thick and varied capping of Glacial 

 deposits which come down onto the Silver Sands in the northern 

 part of the section, but admit the feather-edge of the Gault, along 

 with its basement-beds, in the southern part, which alone is figured. 

 This is at present the best section exposed in the plateau-drifts of 

 the district ; but there is an old much-overgrown pit 500 yards 

 farther north (just beyond the edge of the sketch-map, fig. 1, p. 2) 

 which appears to have revealed a similar thickness and sequence of 

 boulder-clays, with the addition of coarse morainic gravel at the 

 base. In the pits on lower ground, the drift, having been eroded, 

 is usually scanty or absent, or is of the redeposited gravelly type 



^ W. Keeping-, ' On the Included Pebbles of the Upper Neocomian Sands ' 

 Geol. Mag-. 1880, pp. 414-22 ; in which it is suggested that chert of this kind 

 has been derived from Carboniferous strata. 



