Jurassic tectonics of northeastern Gondwana: Evidence from the detrital zircon record of the Nambour Basin

Abstract: The Nambour Basin provides the easternmost record of Jurassic sedimentation for Australia. U-Pb detrital zircon age spectra constrain basin infill as Early-Middle Jurassic (c. 195–163 Ma). Early Jurassic samples are dominated by 650–500 Ma detrital zircon sourced from the Lachlan Orogen of southeastern Australia. Distal Jurassic upland associated with this orogen was generated by epeiric uplift. Sediment sourced from it was transported northwards and eastwards into the Nambour Basin as corroborated by basinal paleocurrent data. In contrast, Devonian to Triassic detrital zircon from the New England Orogen, which abuts the Nambour Basin margin, are scarce. Topographic relief across this orogen generated by the Permo-Triassic (c. 260–230 Ma) Hunter Bowen Orogeny, had been largely eliminated by the Early Jurassic. Dominant Jurassic detrital zircon for one sample of this age, combined with related paleocurrent data and the absence of a Jurassic zircon source in eastern Australia, reflects an easterly Jurassic igneous assemblage now located on submerged northern Zealandia. The detrital zircon data presented herein constrains tectonic interpretations proposed for Jurassic east Gondwana, continental margin sedimentary assemblages in New Caledonia and New Zealand. Documentation of continental epeiric uplift from detrital zircon age data obtained from basin fill has potential yet to be explored.