Compositional trends in the Permian sandstones from the Denison Trough, bowen basin, queensland reflect changing provenance and tectonics

Abstract

Point-count data of sandstone samples collected from six sedimentary formations encountered in boreholes in the Permian sequence of the Denison Trough (an Australian backare/ retroarc foreland basin) provide information about the tectonic evolution of their source areas and the depositional sites. Plots of the detrital compositions of these Permian sandstones against borehole depths indicate that the Reids Dome Beds sandstones, containing highly abundant lithic/volcanolithic grains, mark the onset of intense compressional tectonics and arc volcanic activities to the east accompanied by extensional tectonics and subsidence in the trough. Folding and thrusting owing to intense compressional tectonics in the New England Fold Belt and Arc volcanism in the Camboon Volcanic Arc region to the east generated a great supply of recycled sediment and volcanic detritus that led to a rapid infilling of the subsiding Denison Trough during formation of the Reids Dome Beds sandstones in Early Permian time. The detrital composition of the sandstones of the overlying Cattle Creek Formation, Aldebaran Sandstone, and the Freitag Formation indicate gradually decreasing compressional tectonics and arc volcanism accompanied by increasingly dominant sediment-supply from the stable continental craton to the west. The Freitag Formation sandstone compositions mark the quietest tectonic and volcanic episode in the region, accompanied by subsidence of the Denison Trough owing to thermal cooling during the Middle Permian. The Peawaddy Formation and the Bandanna Formation sandstone compositions represent a Late Permian renewal of compressional tectonics and arc volcanism to the east accompanied by uplift and folding of the sedimentary strata, resulting in the formation of largely fluvial depositional environments in the Denison Trough. Modal compositions of the Bandanna Formation sandstones indicate that renewed arc volcanism and compressional tectonic activity attained maximum intensities during the Late Permian.