Stratigraphic resolution of a multiphase intracratonic basin system: The McArthur Basin, northern Australia

Abstract

The McArthur Basin is a regionally extensive multiphase Proterozoic basin system in northern Australia. Existing lithostratigraphic elements are amalgamated into five coherent basin phases or ‘packages’, to provide a basin‐wide informal and non‐genetic stratigraphic framework on which future genetic models may be based. Packages are basin‐scale depositional and magmatogenic rock units, equivalent in magnitude to 2nd‐order basin cycles. Each package comprises a set of lithostratigraphic units with similar age, stratigraphic position, lithofacies or lithofacies associations, style and composition of volcanism, basin‐fill geometry and depocentre. The Redbank package (ca 1815–1710 Ma) comprises up to ∼6 km of shallow‐marine to fluvial sandstone, and lesser lutite, conglomerate, dolostone and bimodal volcanic and shallow intrusive rocks. It forms a semi‐contiguous sheet throughout most of the McArthur Basin, but thins against the large‐scale basin‐compartmentalising basement ridges (e.g. Murphy and Urapunga Tectonic Ridges) due to depositional onlap and/or differential erosion. The conformably overlying Goyder package (ca 1710–?1670 Ma) comprises shallow‐marine to fluvial sandstone and minor lutite and carbonate. It is areally restricted with a distinct ∼6 km‐thick depocentre in the central Walker Fault Zone (the proto‐Walker Trough) and is flanked by attenuated successions onlapping the adjacent shelves suggesting deposition in a synsedimentary ‘rift’. The conformably or disconformably overlying Glyde package (?1670–1600 Ma) comprises ∼5 km of stromatolitic‐evaporitic dolostone, siliciclastics and minor tuffaceous rocks, deposited in shallow‐ to moderately deep‐water and locally emergent environments. It is restricted to the Walker, Batten and Urapunga Fault Zones, subsequent to deposition in the fault‐bounded Walker and Batten Troughs. The unconformably to disconformably overlying Favenc package (ca 1600–?1570 Ma) is a regionally extensive, ∼50–1600 m‐thick, stromatolitic and evaporitic dolostone‐sandstone succession with minor basaltic volcanics deposited in shallow‐water, marginal‐marine, peritidal‐shelf and/or continental sabkha settings. It was deposited as a series of broad interconnected sag basins that transgressed the pre‐existing tectonic framework of troughs and shelves. The Wilton package (?1500-?1400 Ma) is a widely distributed cyclic sequence of siliciclastics deposited in a shallow‐marine, nearshore to shelf environment. It unconformably overlies all older basin packages, transgressing the pre‐existing tectonic elements of the McArthur Basin. Distribution and depocentres have evolved significantly from the underlying packages, the Wilton package thickening to ∼5 km in the Beetaloo Sub‐basin.