U-Pb detrital zircon geochronology of the Middle to Upper Jurassic strata in the Surat Basin: New insights into provenance, paleogeography, and source-sink processes in eastern Australia.

New U-Pb detrital zircon ages from sandstones have been determined for the Walloon Coal Measures-Springbok Sandstone section of the Surat Basin. In the late Jurassic Surat Basin, there is a shift from relatively thick coal measures – the Walloon Coal Measures – consisting of laterally discontinuous coal-seam horizons intercalated with lithic sandstones and mudstones to an overlying coal-poor sandstone-dominated unit – the Springbok Sandstone – that is more laterally continuous. Across the basin, the contact between the two units varies from transitional to unconformable, and the sandstone becomes less lithic. The nature of the contact and the compositional variability of the sandstone across the basin have implications for predicting communication between gas production fields and potential aquifers in the Walloon Coal Measures and overlying Springbok Sandstone. This study tests whether detrital zircon age (LA-ICP-MS) populations from sandstones within these two units can identify provenance shifts and potential tectonic drivers for basin infill at this time. Detrital zircon ages of both units, informed by paleocurrent measurements showing a southerly flowing depositional system, suggest sediment was sourced from three distinct terranes: the Thomson Orogen in northeastern Queensland; Permian-Triassic granitic intrusions emplaced within the northeast New England Orogen during the Hunter-Bowen Orogeny accretion event; and an inferred but now eroded Jurassic magmatic-arc located along the eastern margin of Gondwana. Two major source-delivery systems, named here Western and Eastern Source systems, are recognized by distinct detrital zircon age populations in both formations in the northern Surat Basin. The Western Source of the Walloon Coal Measures delivered substantial Jurassic age zircons, with minor Pre-Cambrian input; the Eastern Source delivered substantial reworked Precambrian and lesser Jurassic zircons. In contrast, the Western Source of the Springbok Sandstone delivered substantial Jurassic and distinct Triassic zircons dated between ca 234 Ma and 224 Ma in the north-west, while the Eastern Source delivered more pronounced Pre-Cambrian input, with minor Jurassic and absent or minor age zircons in the northeast. Maximum depositional ages for the Springbok Sandstone are approximately 2 Ma younger in the northwestern than in the northeastern Surat Basin. The westward younging could be due to migration of the system and/or differential movement on the bounding faults. • New insights into spatial and lateral provenance shift between the Middle-Late Jurassic strata, northern Surat Basin. • Multiple fluvial depocenters identified in the northern Surat Basin using U-Pb detrital zircon geochronology. • Potential reactivation of fault system may have caused a provenance shift between the Middle-Late Jurassic strata in Surat Basin • The detrital age populations when combined with MDAs and published CA-TIMS reveal a younging trend from east to west. [ABSTRACT FROM AUTHOR]

Copyright of Marine & Petroleum Geology is the property of Elsevier B.V. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)