On the Infralias in Yorkshire

Abstract

Comparatively little attention has been paid to the Lias of Yorkshire for some time past; and consequently it is behind the Lias of other parts as to our knowledge of it. This is especially the case with the lowest beds—the zones of Ammonites angulatus and Am. planorbis —constituting the so-called Infralias, whose presence has as yet been scarcely even recognized. It has long been known that Am. angulatus occurs at Redcar, under the name of A. Redcarensis ; and blocks of stone containing Am. planorbis (syn. erugatus ) are thrown up on the coast; but no section, or list of fossils, has as yet been given of the beds. In the present paper I hope chiefly to describe some remarkable sections at Cliff, near Market-Weighton, where the Infralias is well exposed, and the fauna it contains is large and interesting. But, while I describe this as the Infralias of Yorkshire, I must express my opinion that it does not form part of the typical Yorkshire basin. On glancing at a geological map of this part of England, it will appear probable that there has existed a ridge in Carboniferous-Limestone times, stretching west from a little south of Flamborough Head, which has separated the coal-basin of South Yorkshire from that of Durham, and made a gap in the overyling Permian rocks; and though the New Red Sandstone does not appear to be affected by it, all the overlying Jurassic beds are bent round in a curve on its north side, and to the south