Flow Structures in Sedimentary Rocks

Abstract

A number of oriented sedimentary structures from graywacke sequences in North Lancashire and Devonshire, England, are described and their origin discussed. It is concluded that they originated by horizontal flow of sediment, induced either by the drag of the depositing current or by sliding down a slope. In the Lancashire examples these "flow casts" indicate a direction of movement corresponding to that shown by the associated flute casts and groove casts. In the Devonshire examples these directions do not coincide, and it is suggested that this may be due to the eroding current flowing transversely across a sea-bed slope, which subsequently controls the direction of the depositing flow.