J23 
CHAPTER V. 
LOWER LIAS (continued). 
LOCAL DETAILS. 
Harptree and Ckeicton Mendip. 
NORTH of the Mendips the direction of the Liassic outcrop is 
very irregular, and straggling outliers extend westwards on to 
the plateau of Carboniferous Limestone on Broadfield Down. 
It may be remarked that the Lias, and also the Rliaetic Beds, 
overlap the New Red Marl in places, so as to repose directly on the 
Carboniferous Limestone, the Lower Limestone Shales and the 
Old Red Sandstone in the Mendip Country, and on the borders 
of the Bristol Coal-field ; but there is seldom any evidence to 
show that these beds anywhere rest directly on the Coal-measures, 
or even on the Millstone Grit, there being, in nearly all case?, 
evidence of intervening masses of Red Marl or Dolomitic Conglo- 
merate. The exceptions are near Babington and Holcombe, 
where the Lower Lias is represented, on the Geological Survey 
Map, as reposing directly on the Coal-measures ; at Doynton, 
north of Bath, where it rests on the Millstone Grit; and near 
Emborrow, where it rests probably on the same formation. 
A remarkable set of arenaceous and cherty beds of RhaBtic and 
Liassic age, occurs in the neighbourhood of Chevvton Mendip, on 
Harptree and Egar Hills, at East End, Emborrow, and near 
Binegar. 
Attention was directed to them aa early as 1819 by Thomas Weaver,* who 
gave the fullest particulars we have of the strata, but assigned them with 
doubt, to the age of the cherty beds (of Upper Greensand age) on the Black- 
down Hills of Devonshire. A few years later (1823), Buckland and Conybearef 
described the cherty beds, noticing the occurrence of Ammonites and other 
fossils, some of which have been chalcedonized, while others occur in the state 
of casts. These geologists, however, referred the beds (with hesitation) to the 
Dolomitic Conglomerate, because somewhat similar (though unfossiliferous) 
cherty beds are associated with that formation, at Eastwood House, and on the 
hill above it, near East Harptree, and near Green Down Cottage. During the 
progress of the Geological Survey the beds were recognized by De la BecheJ 
as of Liassic age ; and in the re-survey in 1868, the cherty beds of Liassic and 
Triassic age were separately mapped by myself. 
The cherty Liassic deposit reposes on the Dolomitic Conglo- 
merate, the Carboniferous Limestone, and Old Red Sandstone : 
and probably also on the Millstone Grit. The strata must in 
places attain a thickness of at least 30 feet, but in the absence of 
any^ continuous section, showing the whole of the beds, this 
estimate is approximate. 
As remarked by Buckland and Conybeare, the high ground 
above East Harptree "is covered with blocks of the chert, which 
* Traus. Geol. Soc,, eer. 2, vol. i. p. 364. 
f Ibid., p. 294 ; Conybeare and Phillips, Geol. England and Wales, p. 304. 
J Mem. Geol. Survey, vol. i. p. 277. 
Geol. E. Somerset, &c., p. 105. 
