Evolution of the Girilambone regolith landscape, central-western New South Wales

Abstract

A model of regolith and landscape evolution for the Girilambone region is derived from regolith–landform mapping and interpretation of drillhole information, the latter being underpinned by detailed petrography and Portable Infrared Mineral Analyser (PIMA) characterisation. The model is partly constrained by the interpretation of palynological, paleomagnetic, apatite fission-track, and airborne magnetic data. The model interprets the architecture of the three main sediment sequences and explains their derivation: a possible Late Jurassic fluvial sequence, an Early Cretaceous estuarine–shallow-marine and fluviolacustrine sequence (both sequences being part of the Surat Basin), and a Late Pliocene to Holocene colluvial–alluvial sequence. Implications of this model are that much, if not all, of the Cobar Uplands was covered by a shallow sea in the Early Cretaceous, and that neotectonic reactivation of north-trending Paleozoic faults caused the formation of the north-plunging depressed zone that contains the Mulga–Tindarey Paleovalley System.

Key Words:

• Cretaceous
• Girilambone–Cobar region
• landscape evolution
• neotectonics
• PIMA regolith attributes
• regolith

Acknowledgements

A large multidisciplinary team of scientists and Honours and PhD students from core parties in CRC LEME were involved in various aspects of gathering, analysing and interpreting data for the Girilambone Project. Angelo Vartesi and Travis Naughton, Visual Resources Unit, CSIRO Exploration and Mining, Perth, prepared the figures. This paper is published with the permission of the Chief Executive Officers of Geoscience Australia and CRC LEME.