STRATIGRAPHIC ARCHITECTURE OF THE UPPER PERMIAN BETTS CREEK BEDS IN THE NORTHEASTERN GALILEE BASIN, QUEENSLAND, AUSTRALIA

The Upper Permian Betts Creek Beds form a succession of coal-bearing alluvial plain sediments in the northeastern Galilee Basin, Queensland, Australia. The unit, ~100 m in thickness, outcrops within Porcupine Creek National Park and is laterally continuous for several kilometers. The unit is comprises predominantly conglomerate and sandstone bodies at the base, and siltstone, mudstone, and coal seams at the top. Previous interpretations have reported an entirely nonmarine depositional setting for the unit, however, a heavily bioturbated mudstone bed containing traces fossils (Diplocraterion habichi, Conichnus sp.) is observed below coal-bearing intervals indicating a transgressive period within the basin.

Models of coal-bearing alluvial successions have not advanced significantly within the last several years and many lack sufficient detail. The outcrop quality of the Betts Creek Beds allow for a detailed three-dimensional study of the stratigraphic stacking patterns of such successions, which will contribute to previously proposed models. The quality of exposure also allows a test of recent proposals that coal seams within coal-bearing alluvial successions are sheet-like and of regional extent. If such assertions are well-founded, coal seams could be used as regional stratigraphic markers, as evidence of regional flooding surfaces, and hence could be utilized to predict the distribution of rock bodies in the subsurface. Such a model is, nonetheless, largely untested by high-quality data from well-exposed outcrop examples. The geometry of coal seams within the Betts Creek Beds are thus relevant to exploration for natural hydrocarbon resources, specifically in the Upper Permian successions elsewhere in Australia such as in the Cooper Basin of central Australia.