Stratigraphy of the Upper Permian Kennedy Group of the onshore Carnarvon Basin (Merlinleigh Sub-basin), Western Australia

Abstract

Upper Permian strata contain many examples of cyclic deposition, despite the prevailing view that greenhouse conditions existed at the time. The shallow marine Upper Permian Kennedy Group, onshore Carnarvon Basin, has been studied in detail in the Kennedy Range 150 km east of the town of Carnarvon, Western Australia. The Kennedy Group exhibits cyclicity on a scale of 3-10 m, and also some larger scale changes in sedimentation. In this study, the Kennedy Group is divided into twelve informal units, designated with letters from A to L. The small-scale cyclicity consists of stacked regressive cycles that comprise only thin highstand systems tracts and regressive systems tracts. Transgressive systems tracts are only sometimes represented by highly bioturbated green sandstone layers at cycle boundaries. Cycle tops are planar and often have extensive vertical trace fossil development down from them, as well as surface traces on them. The twelve informal units can be interpreted as being caused by changes in relative sea-level.