Page:Quarterly Journal of the Geological Society of London, vol. 33.djvu/38

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16
D. C. DAVIES ON THE UPPER CARBONIFEROUS

of group 2, which are sometimes gypsiferous, become in other places coarse grits interlaminated with sandstones and yellow, white, and greenish marls, which contain plants and small seams of impure coal. Group 3 is variously described. In places it is made up of limestones and marls, in others of red grits and conglomerates, and, again, of red sands with copper ores; occasionally there is much sulphur and asphalte. Group 4 consists of sandstones and conglomerates.

Section 2 is one given by Mr. Binney[1] of the strata at Canobie. Mr. Binney describes the upper Coal-measures, group 1, as the highest in the kingdom. He considers the Permian to begin with the lowest breccia in group 2. These breccias are made up of Carboniferous gritstones and limestones. They are interstratified with red shales containing rootlets of Stigmaria ficoides, and also with a bed of limestone together with brown sandstones. Group 3 consists of red shaly clays with bands of gritstone and thin veins of gypsum. These are surmounted by a brown sandstone (group 4), which Mr. Binney considers to be the equivalent of the sandstone of Shawk and St. Bees on the south, and of Glenzier and Cove on the north.

Section 3 is the one I have already referred to as described by the late Sir R. I. Murchison and Prof. Harkness[2]. They describe the base of group 2, as consisting chiefly of fragments of Carboniferous Limestone; this is succeeded by red sandstone, followed by breccias which are sometimes rotten, and which are capped by rocks containing quartz-crystals passing into fine-grained breccia containing fragments of slate rocks. They give the thickness of this group as 2000 ft.; but this estimate should, I think, be taken with some reserve. The base of group 3 is interesting as being composed of shales from which the authors collected the following plant-remains:—

Sphenopteris Naumanni.
——— dichotoma.
———, sp.
Alethopteris Gœppertii.
Ullmannia selaginoides.
——— Bronni.

Odontopteris, sp.
Cardiocarpon triangularis.
Portions of coniferous wood.

The impure limestones of this group, the authors take to be the equivalent of that of Barrowmouth, and together with that, the equivalent also of the more largely developed magnesian limestones of the north-eastern counties.

The sandstone of group 4, they describe as being identical in mineral character with sandstones on the same horizon in East Cumberland and Westmoreland.

Section 4 was originally described by the late Prof. Sedgwick[3],

  1. "Triassic Strata of Cumberland and Dumfries," Memoirs of the Philosophical Society of Manchester, vol. ii. 3rd series, p. 315 et seq.
  2. "The Permian Rocks of the North-west of England," Quart. Journ. Geol. Soc. vol. xx. p. 144.
  3. Geol. Soc. Trans, new series, vol. iv. p. 398.