A marine shell-bed near the base of the Estuarine Series in Raasay

Abstract

The purpose of this paper is to place on record the discovery of a marine shell-bed near the base of the Estuarine Series of the Jurassic succession in the island of Raasay in the Inner Hebrides. The author acknowledges with thanks the assistance of Dr. Martin Bott, Mr. C. R. Thewlis and Mr. D. Williams who all took part in the discovery. He also records his grateful thanks to Dr. L. R. Cox who identified and commented upon the lamellibranchs and to Dr. F. W. Anderson who identified the ostracods and crinoids collected from the shell-bed. The field work was carried out with the aid of a grant from the Clough Memorial Research Fund, which is gratefully acknowledged. In the Hebridean province of the British Jurassic rocks, the Inferior Oolite Series is followed by strata of estuarine origin known as the Great Estuarine, or simply the Estuarine, Series. This series is regarded as the equivalent of the Great Oolite Series of southern England, but may include at its base strata of inferior Oolite age as well. Arkell (1933, p. 246) noted that the topmost ammonite zones of the Inferior Oolite have not been found in the Hebrides, but the succession upwards from the highest known beds in that Series, namely those of the Garantiana Zone , was believed by Lee to be a conformable one. He stated (1920, p. 53) that in Raasay, “The actual base of the series” (i.e. of the Estuarine Series) “is marked by an oil-shale, 8 to