Palaeozoic synorogenic sedimentation in central and northern Australia: a review of distribution and timing with implications for the evolution of intracontinental orogens

ABSTRACT

The Palaeozoic Alice Springs Orogeny was a major intraplate tectonic event in central and northern Australia. The sedimentological, structural and isotopic effects of the Alice Springs Orogeny have been well documented in the northern Amadeus Basin and adjacent exhumed Arunta Inlier, although the full regional extent of the event, as well as lateral variations in timing and intensity are less well known. Because of the lack of regional isotopic data, we take a sedimentological approach towards constraining these parameters, compiling the location and age constraints of inferred synorogenic sedimentation across a number of central and northern Australian basins. Such deposits are recorded from the Amadeus, Ngalia, Georgina, Wiso, eastern Officer and, possibly, Warburton Basins. Deposits are commonly located adjacent to areas of significant basement uplift related to north–south shortening. In addition, similar aged orogenic deposits occur in association with strike-slip tectonism in the Ord and southern Bonaparte Basins of northwest Australia. From a combination of sedimentological and isotopic evidence it appears that localised convergent deformation started in the Late Ordovician in the eastern Arunta Inlier and adjacent Amadeus Basin. Synorogenic style sedimentation becomes synchronously widespread in the late Early Devonian and in most areas the record terminates abruptly close to the end of the Devonian. A notable exception is the Ngalia Basin in which such sedimentation continued until the mid-Carboniferous. In the Ord and Bonaparte Basins there is evidence of two discrete pulses of transcurrent activity in the Late Devonian and Carboniferous. The sedimentological story contrasts with the isotopic record from the southern Arunta Inlier, which has generally been interpreted in terms of continuous convergent orogenic activity spanning most of the Devonian and Carboniferous, with a suggestion that rates of deformation increased in the mid-Carboniferous. Either Carboniferous sediments have been stripped off by subsequent erosion, or sedimentation outpaced accommodation space and detritus was transported elsewhere.