Geochemical reconstruction of the provenance, weathering and deposition of detrital-dominated sediments in the Perth Basin: The Cretaceous Leederville Formation, south-west Australia

Abstract

The deep (> 10 km) Permian to present day Perth Basin in southwest Western Australia is composed of sedimentary successions of continental to shallow marine origin. This study examines the compositional variation, weathering and provenance of the early Cretaceous Leederville Formation within the Perth Basin. Over 200 sediment samples were retrieved from two deep boreholes of ~ 350 to 530 m in depth encompassing the Leederville Formation, and analysed for major and trace element geochemistry and mineralogy. The Leederville Formation is composed of subarkosic sands, predominantly composed of quartz (64%) and K-feldspars (27%); silts and clays composed of kaolinite (24–54%), K-feldspars (20–29%) and quartz (18–40%), with their compositional variation reflecting weathering, hydraulic sorting during transport, mostly subaqueous deposition and subsequent diagenesis. Most trace elements are associated with fine grained lithologies due to their occurrence within clays, sulphide or zircon. Major and trace element geochemistry suggests a typical passive margin origin with minimal intrabasinal sediment recycling. The regionally extensive Yilgarn Craton, appears to be the main sediment source for the Leederville Formation within the study area.