Fossils from the Fuller's Earth of the Weymouth Anticline

Abstract

Fuller's Earth was first recorded at the surface in the core of the Weymouth anticline by Damon (1860, p. 12). It was mapped by the Geological Survey in a semi-elliptical area south of Langton Herring, having a sea coast of about 1¼ miles on the West Fleet (1 inch map, sheet 341). The chief feature of interest is a lumachelle or oyster bed composed of a mass up to some 12 feet thick of the small oyster, Ostrea hebridica Forbes (= 0. sowerbyi Morris and Lycett), the var. elongata Dutertre predominating (see Damon, 1860 and 1884, p. 12, fig. 3). The oyster was recorded by Damon and by Strahan (1898, p. 5, and sheet 341) as O. acuminata J. Sowerby, but that species belongs to a lower horizon, below the Fuller's Earth Rock. The Langton Herring oyster bed, which is seen also at Watton Cliff near Bridport, lies in the Upper Fuller's Earth, above the Fuller's Earth Rock, which does not come to the surface in the Weymouth anticline. The lowest beds exposed in the anticline, for a few feet below the oyster bed, are tough clays with mudstone nodules and abundant Rhynchonella smithi (Davidson) (see Arkell, 1933, p. 252). With the Rhynchonellids there weather out also abundant fragments of a typical Fuller's Earth belemnite, which I follow some French authors in calling Belemnopsis bessina (d'Orb.).