Sediment provenance analysis of the early Permian reservoirs of the Perth Basin

Abstract

The sediment provenance of Early Permian reservoirs (‘Kingia’ and High Cliff sandstones) of the onshore North Perth Basin is poorly understood. Bulk rock inorganic geochemistry, detrital zircon geochronology and heavy mineral data have been used to assess spatial and temporal changes in provenance in the vicinity of the Waitsia, Lockyer Deep, West Erregulla and Beharra Springs Deep discoveries. The geochemical data provides a chemostratigraphic framework for the Early Permian that can be confidently correlated throughout the basin. The detrital zircon and Raman data have recognised significant regional variabilities. The zircon data defines western and eastern regions that were separated and/or infilled by different depositional systems, likely defined by the Mountain Bridge Fault. Raman analysis demonstrates that the High Cliff and ‘Kingia’ sediments in the vicinity of Waitsia have different zircon age populations and heavy mineral assemblages, with the ‘Kingia sandstone’ dominated by apatite indicating access to a granitic source at this time. This is poorly represented by wells in the northern Dongara Terrace and Allanooka Terrace, where sediments are dominated by garnet. Analysis of Lockyer Deep and West Erregulla discovery wells in the northern Dandaragan Trough, also demonstrate only minor amounts of apatite, but also include a significant mafic component, the source of which is uncertain. The geochemical data demonstrates that the top of these reservoirs is defined by a highly consistent change in provenance, coincident with a switch to garnet-rich sediments and different dominant zircon age populations.