Summary of results. Joint NTGS-GA geochronology project: western Warburton Basin, March 2022-February 2023

Abstract

This Record presents data collected during March 2022–February 2023 as part of the ongoing Northern Territory Geological Survey–Geoscience Australia SHRIMP geochronology project under the National Collaborative Framework agreement and Geoscience Australia’s Exploring for the Future Program. New SHRIMP U–Pb zircon geochronological results were derived from sedimentary rock chip samples of the Warburton Basin collected from four petroleum exploration wells (Beachcomber 1, Thomas 1, Simpson 1, Colson 1) located in the southeastern corner of the Northern Territory. Geologically, this is a region in the Simpson Desert that encompasses several superimposed intracratonic sedimentary basins, which are separated by regional unconformities and extend over areas of adjoining Queensland, South Australia and New South Wales. The exposed Mesozoic Eromanga Basin overlies the late Palaeozoic Pedirka Basin, which is largely restricted to the subsurface. Below these basins lies the Warburton Basin, an early Palaeozoic pericratonic basin containing an early Cambrian and Ordovician succession (Edgoose and Munson 2013), with possible Devonian rocks in some areas (Radke 2009). Understanding of the geology of the NT portion of the Warburton Basin is hindered by the absence of surface exposures, scarcity of intersecting drillhole data, limited biostratigraphic age control, and relatively sparse seismic data coverage.

The sample analysis results reported herein were collected to improve knowledge of the chronostratigraphy and provenance characteristics of the concealed Warburton Basin. All four sedimentary samples are dominated by Mesoproterozoic detritus (ca 1000–1300 Ma), with few zircons of Paleozoic age, and generally sparse older Palaeoproterozoic–Archaean-aged zircons. Samples from the two westernmost wells yielded 238U/206Pb maximum depositional ages of 469 ± 9 Ma (Colson 1) and 394 ± 6 Ma (Simpson 1). Samples from the two easternmost wells yielded older 238U/206Pb maximum depositional ages of 569 ± 10 Ma (Thomas 1) and 506 ± 5 Ma (Beachcomber 1). These data imply that known Devonian (419–359 Ma) stratigraphy of the basin extends at least as far as the Simpson 1 well, but may not extend further east.