540 L. Richardson — Lias Sections, Batcomhe, Somerset. 



y. — On some Middle and Upper-Lias Sections neak Batcombe, 



Somerset. 



By L. Richardson, F.R.S.E., F.G.S. 



IIS" 1906 I described, in this Magazine,^ a section at Maes Down, 

 between Evercreech and Doulting, in which the Marlstone of the 

 Middle Lias and certain Upper-Lias beds were exposed. The main 

 interest of this section lay in the fact that the beds exposed occurred 

 in a tract that had been mapped as Inferior Oolite resting upon 

 Midford Sands, and these in turn directly upon the Lower Lias 

 without the intervention of any Middle Lias. Naturally it was 

 wondered what had become of the Middle Lias. This Maes-Down 

 section therefore proved the presence of typical Marlstone and certain 

 basal Upper-Lias beds (consisting of thin alternating layers of clay 

 and limestone), while on the higher ground, above the level of the 

 quarry, are unmistakable signs of Midford Sands. 



Although I have inspected the hill-slopes between Maes Down and 

 Chelynch (on the slopes of the Mendips), I have failed to find any 

 exposure that throws light upon the probable northerly extension of 

 the Middle Lias, or the relations of that stage to the Lower Lias. 



The Midford Sands, however, are very fairly exposed at the top of 

 the bank on the south side of the road, close to the south-eastern 

 corner of the Doulting Sheep Sleight ; and ammonites indicative of 

 striatuU hemera have been procured from a limestone-bed in the bank 

 by the side of the main-road, where it climbs the hill between Shepton 

 Mallet and Doulting.^ 



In the hills between Maes Down and Bruton it is probable that the 

 sequence is everywhere in ascending order : (1) Marlstone ; (2) Upper- 

 Lias clays and limestones ; and (3) Upper-Lias Sands. The Marlstone 

 and basal Upper- Lias clays and limestones are excellently displayed in 

 the quarry at Small Down, and in that in Westcombe village, near 

 Batcombe ; while the Sands are deeply-incised by the lane that 

 descends Lamyat Beacon in the direction of Week Charapflower. 



Sir Henry de la Beche assigned a thickness of 2 1 feet to the 

 Marlstone at Scale Hill, near Batcombe, and estimated the thickness 

 of the Upper-Lias deposits at 66 feet.^ Commenting upon Sir H. de la 

 Beche's estimates, Mr. H. B. Woodward, F.R.S., writes that the 

 " Marlstone, although present, does not appear to comprise a mass of 

 strata 21 feet thick, as stated by him".* It maybe too liberal an 

 estimate (if it does not include the underlying " sandy beds " of the 

 Middle Lias), but still the Marlstone is very well-developed in this 

 neighbourhood, as the two sections I am about to record demonstrate. 



The fiirst section to notice is that on the western slope of the camp- 

 crowned hill, about half-a-mile to the south-east of Chesterblade. 

 Locally, it is called the " Small-Down Quarry". It is a little 

 difficult to indicate on the one-inch Geological Survey Map, sheet xix, 



1 Geol. Mag., Dec. V, Vol. Ill, 1906, pp. 368-9. 



~ Quart. Joura. Geol. Soc, 1907, vol. Ixiii, p. 391 ; Geol. Mag., 1908, p. 510 

 (footnote). 



^ Mem. Geol. Surv., 1846, vol. i, p. 280 (footnote). 



* Mem. Geol. Surv., 1893, vol. iii, p. 207 : " The Jurassic Rocks of Britain : The 

 Lias of England and Wales (Yorkshire excepted)." 



