Page:VCH Warwickshire 1.djvu/47

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GEOLOGY Keuper Sandstone, occur within the Marls, but they are somewhat impersistent. They are well developed in the neighbourhood of Henley- in-Arden, where they form some picturesque escarpments. These beds received much attention from the late Mr. Brodie of Rowington ; there they have yielded some few fossils, including the heterocercal fish Dictyo- pyge (Palaoniscus) superstes. 1 The bivalved phyllopod crustacean Estberia minuta, with remains of fishes (e.g. Acrodus], Labyrinthodon^ reptilian footprints, and plants were found at Shrewley by Mr. Brodie; 2 and more recently at the latter place some molluscs, probably marine according to Mr. R. B. Newton, 3 were found by Messrs. Brodie and E. P. Richards in some green gritty marls associated with the Upper Keuper Sandstone. The highest beds of the Marl are pale green in colour, the iron oxides not being in a state of complete oxidation. They are generally known as the Tea-green Marls and have in some localities been grouped with the Rhastic beds; but in other districts they are more closely associated with the Keuper. The highest beds of these green marls are succeeded by a thin series of fossiliferous black shales, grey marls, and limestones of marine origin which constitute the Rhastic beds; they form a passage group into the Lias, and generally show a two-fold subdivision : P. . ( White Lias group; grey shales and limestones.

Avicula contorta shales; black paper-shales with one or more 

bone beds and thin seams of yellow sandstone. The whole of the beds are richly fossiliferous ; the characteristic species of the lower part are the lamellibranchs Avicula contorta, Pecten valoniensis, and Pullastra arenicola. The higher beds or White Lias con- tain Cardium rbceticum, with Ostrea liassica and Modiola minima, allied respectively to our modern oyster and mussel. The bone beds are bands, one or more inches thick, abounding in rolled and broken teeth and bones of fish. In Warwickshire the Rhastic beds are probably present between the Keuper Marls and the Lias from one end of the county to the other ; but the amount of information concerning them is small. At Binton, west of Stratford-on-Avon, they have been described by Dr. Wright * and also by Mr. R. F. Tomes; 6 according to the latter the uppermost beds consist of greenish-grey clay, 6 succeeded by the Guinea Bed, a hard crystalline limestone one foot thick, deriving its name from its property of ringing under the hammer. This limestone is highly fossiliferous and contains a mixture of Liassic and Rhastic forms, the latter probably incorporated with Liassic forms in their present position by the breaking down of a previously deposited Rhastic bed. On this account Mr. H. B. Woodward would regard the Guinea Bed as the lowest bed of the Lias. Rhaetic beds are known to occur at Wootton Park near Alcester, and at 1 Egerton, Quart. Journ. Geol. Sx. xiv. (1858), 164. 2 Quart. Journ. Geol. Sac. xii. (1856), 374. 3 Journ. Conchology, vii. (1894), 408. 4 Quart. Journ. Geol. Soc. xvi. (1860), 374. 6 Ibid, xxxiv. (1878), 179. 6 See section in H. B. Woodward's ' The Jurassic Rocks of Britain,' Mem. Geol. Survey, iii. 151. i 17 3