U-Shaped Burrows in the Lower Lias of Somerset and Dorset

Abstract

The weathered surfaces of the limestones and calcareous shales of the Lower Lias in Somerset and Dorset sometimes exhibit curious paired markings. On careful examination these prove to be cross sections of U-shaped burrows of organic origin, appearing as two circular markings connected by a shallow depression or by a slight variation in the character of the matrix. Similar burrows have been described from the Lower Estuarine sandstone of Blea Wyke, on the Yorkshire coast. Dr. F. A. Bather has discussed their origin and structure in detail and has assigned them to the genus Arenicolites, which was established by J. W. Salter for “all worm burrows with double openings”. Other species of the genus have been described from arenaceous and argillaceous beds of Longmyndian, Ordovician, and Upper Carboniferous age, but as far as the author is aware, the species here recorded is the first that has been mentioned from the calcareous rocks of the Lower Lias of England.