Sequence stratigraphy of the ca 1640 Ma Barney Creek Formation, McArthur Basin, Australia

Abstract

The ca 1640 Ma Barney Creek Formation is a mostly fine-grained silicicastic unit of the McArthur Group in the southern McArthur Basin of northern Australia. It is one of the most prospective units for clastic-dominated (CD-type) Zn–Pb deposits in the world, hosting the giant McArthur River Zn–Pb–Ag and the Teena Zn–Pb deposits. The Barney Creek Formation records deposition of dominantly dolomitic siltstone turbidite facies at or below storm wave base. These strata were deposited in a series of sub-basins and on submerged paleohighs that formed in response to roughly north–south extension during early Barney Creek times. A detailed, regional-scale sequence stratigraphic analysis based on 20 wells indicates that the middle McArthur Group (Emmerugga Dolostone to Lynott Formation) comprises six third-order depositional sequences, of which the Barney Creek Formation includes two (named B1 and B2). These two sequences and the overlying sequence L1 (Reward Dolostone and lower Lynott Formation) record significant lateral facies and thickness changes across the southern McArthur Basin. These variations can be explained by a geographical shift in the depocentre during structural re-organisation of the basin. The depocentre migrated from the south, where accommodation was mostly created during deposition of sequence B1, towards the north during deposition of sequence B2. KEY POINTS Sequence stratigraphic analysis of the Barney Creek Formation on a regional scale based on 20 wells. Barney Creek Formation includes two third-order depositional sequences (named B1 and B2), which record significant lateral thickness and facies shifts. Thickness and facies shifts can be explained by geographical shift of depocentre from the present-day south to north.