Br. R. L. Sherlock — DatuTn-lines in English Keuper. 123 



Leicestershire the gypsiferous belt is seen at Thurmaston Brickyard 

 and at Gipsy Lane Brickyard/ Leicester; but between Cropwell 

 Bishop and Tutbury in Staffordshire the lower horizon of gypsum (to 

 be mentioned later on) is economically the more important one. 

 Near Penarth, in Glamorgan, near Yate, in Gloucestershire, and 

 near Watchet, in Somerset, the upper horizon is being, or has been, 

 worked. 



It is remarkable that although on the west side of Watchet 

 gypsum is abundant enough to be quarried, at St. Audries,^ on the 

 east side of Watchet, it is quite absent. But a band of indurated marl, 

 4 to 6 inches thick, occurs containing celestine, at a depth of 69 feet 

 below the base of the B-hsetic, i.e. at the horizon of the gypsum. 

 At Yate, in Gloucestershire, the celestine deposits occur at the same 

 horizon as the gypsum, but only in one place have the two minerals 

 been found together. We may therefore infer that at St. Audries 

 the absence of gypsum is due to the presence of celestine at the same 

 horizon. 



2. The lower horizon of gypsum is worked extensively in the 

 Gotham district of Nottinghamshire and in East Staffordshire. 

 A bed of gypsum, usually from 7 to 11 feet in thickness, is worked at 

 Gotham, East Leake, Barton, Thrumpton, and Kingston-upon-Soar, 

 all in Nottinghamshire, and the gypsum of Chellaston, Derbyshire, 

 probably belongs to this horizon. In Staffordshire the bed is from 

 8 to 15 feet in thickness, and is worked in the parishes of Hanbury 

 and Draycott. The bed is characterized by a ball-like structure on 

 a large scale, the thicker parts of the seam representing more or less 

 distinctly the sphseroids, and the thinner parts the intervals between 

 them. 'In thickness and sphseroidal structure the bed is fairly well 

 marked off from other beds of gypsum in the Keuper. 



At East Leake the gypsum is said to occur about 150 feet below the 

 Tea-green Marls. This is but a rough estimate, and the thickness of 

 Tea-green Marls is not stated. The Tea-green Marls vary a good 

 deal in thickness, but at Newark, where they are best seen, there is 

 about 18 feet of them. This would give roughly 168 feet of strata 

 between the gypsum and the Ehsetic beds. At Glebe Mine, Gotham, 

 the details of a ventilating shaft have been preserved,^ and show 

 a thickness of 160 feet between the gypsum and the Bhsetic beds. 

 At a depth of 86 feet below the Bhsetic a thick bed of gypsum was 

 found, and this is probably part of the upper belt. At Fauld, near 

 Tutbury, Staffordshire, the gypsum is thought to be about 145 feet 

 below the top of the Keuper Marl. The discrepancy between the 

 depth here and at Gotham may be due to various causes, but a likely 

 one is that, as Rhaetic beds were not separated from Lias when the 

 district was mapped, about 1852, it is probable that the Tea-green 

 Marls have been put with them in the Lias, in accordance with the 

 then current idea that the green marls were part of the Bhsetic. If 



^ For full section see T. 0. Bosworth, The Keuper Marls around Charmvood, 

 Leicester, 1913, p. 117. 



^ Vertical sections, Geol. Surv., Sheet 47, No. 6. 



■^ Special Reports on the Mineral Sources of Great Britain (Mem. Geol. 

 Surv.), vol. iii, p. 26, 1915. 



