‘McArthur’s Zircons, a Tale of Two Arenites’ – provenance and evolution of the Maiwok Sub-Group, McArthur Basin, Northern Territory

Abstract

The Beetaloo Basin is a sub-basin of the ‘greater McArthur Basin’, a >180,000 km2 ca. 1800-900 Ma basin system that covers much of northern Australia and, in its Mesoproterozoic section, hosts extensive hydrocarbon reserves. The nature of the basin and provenance of the rocks within the basin are largely unknown. Here I present detrital zircon U-Pb data from twelve sandstone core samples from the Maiwok Sub-group, and compare them with existing outcrop samples from the Urapunga Region within the McArthur Basin to examine the maximum depositional ages of the formations, to address intra-basin correlation, and examine both temporal and spatial provenance variations. Detritus analysed yielded early Palaeoarchean to early Neoproterozoic ages from sandstone formations of the Maiwok Sub-group, in the Beetaloo Basin (Fig. 1). In the Beetaloo Basin; the Bessie Creek Sandstone formation was deposited between 1386 ± 13 Ma and 1324 ± 8 Ma, and the Moroak Sandstone formation was deposited after1375 ± 15 Ma. The formation logged as the Moroak Sandstone (320.0-391.72m) in Altree 2 drillcore was logged incorrectly. Detrital zircon data has shown this sandstone is too young to be the Moroak Sandstone. I have reinterpreted this interval in Altree 2 as Bukalorkmi Sandstone from 359.5-391.72m and Jamison Sandstone from 320.0-359.5m (Fig. 7). In Altree 2, the Bukalorkmi Sandstone was deposited after 1194 ± 25 Ma and the Jamison Sandstone was deposited between 959 ± 18 Ma and 513 ± 12 Ma. Temporal provenance variations are minimal between the Bessie Creek Sandstone and the Moroak Sandstone, but much greater between the Moroak Sandstone and the Jamison/Bukalorkmi Sandstone formations. The Walton High defines a spatial provenance boundary from the north and the south (Fig. 12). This boundary affects Maiwok Sub-group sandstones, including exposed formations, and has been under appreciated in previous studies.