Early Evolution of the Adelaide Superbasin

Abstract

Continental rifts have a significant role in supercontinent breakup and the development of sedimentary basins. The Australian Adelaide Superbasin is one of the largest and best-preserved rift systems that initiated during the breakup of Rodinia, yet substantial challenges still hinder our understanding of its early evolution and place within the Rodinian supercontinent. In the past decade, our understanding of rift and passive margin development, mantle plumes and their role in tectonics, geodynamics of supercontinent breakup, and sequence stratigraphy in tectonic settings has advanced significantly. However, literature on the early evolution of the Adelaide Superbasin has not been updated to reflect these advancements. Using new detrital zircon age data for provenance, combined with existing literature, we examine the earliest tectonic evolution of the Adelaide Superbasin in the context of our modern understanding of rift system development. A new maximum depositional age of 893 ± 9 Ma from the lowermost stratigraphic unit provides a revised limit on the initiation of sedimentation and rifting within the basin. Our model suggests that the basin evolved through an initial pulse of extension exploiting pre-existing crustal weakness to form half-grabens. Tectonic quiescence and stable subsidence followed, with deposition of a sourceward-shifting facies tract. Emplacement and extrusion of the Willouran Large Igneous Province occurred at c. 830 Ma, initiating a new phase of rifting. This rift renewal led to widespread extension and subsidence with the deposition of the Curdimurka Subgroup, which constitutes the main cyclic rift sequence in the Adelaide Superbasin. Our model suggests that the Adelaide Superbasin formed through rift propagation to an apparent triple junction, rather than apical extension outward from this point. In addition, we provide evidence suggesting a late Mesoproterozoic zircon source to the east of the basin, and show that the lowermost stratigraphy of the Centralian Superbasin, which is thought to be deposited coevally, had different primary detrital sources.

Geochronology and formal stratigraphy of the Sturtian Glaciation in the Adelaide Superbasin

“…The generally minor Stenian population of zircon at c. 1160 Ma suggests provenance from the Musgrave Province (Smithies et al 2008;Wade et al 2008;Smithies et al 2011;Smits et al 2014), but as noted in Lloyd et al (2022), they may be sourced from an as yet undiscovered but inferred late Mesoproterozoic (c. 1300-1000 Ma) source to the east (Wysoczanski & Allibone, 2004;Fergusson et al 2007;Mackay, 2011;Korsch et al 2012). This Stenian zircon population is generally more abundant in samples closer to the eastern and western margins of the basin (Figs.…”

“…Rock samples were prepared for DZ analysis by standard methods at the University of Adelaide (Lloyd et al 2022). Cathodoluminescence images were obtained on either a FEI Quanta 600 scanning electron microscope (for zircon analysed in 2020) or a Cameca SXFive Electron Microprobe (for zircon analysed in 2021).…”

“…The Adelaide Superbasin comprises several named basins and sub-basins that form a large, Neoproterozoic to middle Cambrian sedimentary system at the southeast margin of Proterozoic Australia. Formation of the Adelaide Superbasin initiated at c. 890–830 Ma as a result of the breakup of the Rodinia supercontinent (Powell et al 1994; Preiss, 2000; Lloyd et al 2022). The Adelaide Rift Complex is the largest and oldest of the basins within the Adelaide Superbasin and includes a number of extensional depocentres, including the Yudnamutana Trough (northern Flinders Ranges), Baratta Trough (Olary and eastern Flinders Ranges) and Torrowangee Trough of western New South Wales (Fig.…”

“…Deposition within the Adelaide Superbasin occurred over a duration of ∼300 Ma and stretched from the northernmost regions of South Australia to Kangaroo Island in the south, and east into western Victoria and New South Wales. The superbasin began as an intracontinental rift system that progressed to a passive margin system in the southeast and eastern parts of the basin, yet remained a failed rift in the north (Preiss, 2000; Lloyd et al 2022). The cessation of the Adelaide Superbasin is marked by the Delamerian Orogeny c. 514–490 Ma (Drexel & Preiss, 1995; Preiss, 2000; Foden et al 2006; Foden et al 2020).…”

“…Colours used to fill group level cell are consistent with colours used in later figures. Geochronology data from Lloyd et al (2020) and references therein, van der Wolff (2020), and Lloyd et al (2022). …”