The Sedimentary Structures of the Upper Scamander Sequence and Their Significance

A number of sedimentary structures, which have previously not been described anywhere in Tasmania, are developed in the Scamander Slates and Quartzites, near Upper Scamander. These structures include mar!{ings made in muds that have been preserved as casts on the soles of graded sandstones and coarse-grained siltstones. It is well known that certain sole markings, such as flute casts, indicate the direction of the current responsible for their erosion and infilling. This is confirmed at Upper Scamander, for the distribution of the directions incated by these sole markings is similar to that obtained from an examination of current bedding developed in some sandstones and coarse-grained siltstones. A study of the rock types in the Upper Scamander sequence shows that the deposit " normal " to the area was of muds, whilst sands, coarse silts, and fragments of plants and a marine fauna were brought into the locality by turbidity currents, which probably originated to the south-west. The only evidence of life that existed at the site of deposition is the presence of worm-like grooves that were made on the surface of the muds.