The use of quartz grain microtextures in the study of the origin of sand terrains in Western Australia

The origin of extensive sand terrains which lie inland from the coastal mar gin of Western Australia is contentious, with the debate centering around a n in situ vs. an aeolian origin. To resolve this debate the shape and surfa ce features of sand grains are reported for sandplains, sand dunes and bedr ock for the Victoria Plateau sandplain, which lies in the central west coas tal region of Western Australia. All three components of the Victoria Plate au are similar in grain shape and microtexture. Quartz grains show a combin ation of chemical dissolution and precipitation micromorphology. Characteri stics of dissolution include etch patterning, triangular shaped etch pits a nd solution features. Precipitation forms include edge rounding, silica ven eers and plate- and sheet-like structures. Features such as peeling plates, complex precipitation forms projecting from grain surfaces, adhering parti cles and preserved grain contact faces indicate stability rather than a tra nsport dominated environmental history. The combination of preserved dissol ution and precipitation forms, a dearth of mechanically derived features an d a correspondence between grains in rock and overlying sands points to loc al siliceous sedimentary rocks as the source of the sands. (C) 1999 Elsevie r Science B.V. All rights reserved.