A CARBONIFEROUS LAGOON DEPOSIT WITH SPONGES

Abstract

The frequent occurrence of sponge spicules in the Yoredale Series of North West Yorkshire was noted by Dr. G. J. Hinde1 who also remarked on the association of such spicules with the numerous chert beds present in that series, beds which he considered were formed from the debris of siliceous sponges. Sponge spicules are also common both in the limestones and the calcareous shales, and there is no doubt that sponges were most abundant organisms in the seas in which the Yoredale beds were formed. Entire sponges are, however, rare in the Carboniferous. Only two specimens have been described from the Yoredales— Pemmatites constipatus, G. J. Hinde, and Pemmatites sp., Garwood and Goodyear. The few specimens from the Lower Limestones of Ayrshire, described by Young and Carter as entire specimens, were regarded by Zittel as aggregates of spicules. This paper records the occurrence of a sponge bed packed with fossil siliceous sponges which have been preserved entire and with recognisable form and from which spicules are easily isolated. This sponge bed has been traced in the Carboniferous rocks of the Lake District and in those of the Pennines of Yorkshire, Durham and Westmorland; it is of constant, horizon, and was apparently deposited under lagoon conditions. For the most part the sponges described in this paper occur as small well-defined nodules either in shale or in limestone. When broken they are red or dark grey in colour and, therefore, stand out from the surrounding limestone. The occurrence of this nodular band ...