Changing of the guards: Detrital zircon provenance tracking sedimentological reorganization of a post‐Gondwanan rift margin

Abstract

Understanding the development of sedimentary systems during continental rifting is important for tracking environmental change and lithospheric processes. Conceptual models have been developed for the sourcing, routing and facies architecture of sediments in rift-settings, driven in part by quantitative sediment tracking. Here, we present laser ablation split-stream detrital zircon U/Pb geochronology and Hf-isotopes for post-rift (Cretaceous-Paleogene) clastic sediments from Ocean Drilling Program (ODP) wells and Plio-Pleistocene palaeoshoreline material, from the southern margin of Australia. Provenance results are contextualized through comparison with wellcharacterized source regions and regional pre-and syn-rift sediment reservoirs to track changes associated with Australia-Antarctica separation during East Gondwana break-up. The provenance character of the post-rift sediments studied are distinct from pre-existing sediment reservoirs and demonstrate termination of previously stable sediment routing systems and a dominance of local basement of the Proterozoic Madura and Coompana provinces (~1.2 Ga and CHUR-like Hf-signatures; Moodini Supersuite) in offshore ODP wells. A composite post-rift Cretaceous?-Eocene sample in the easternmost well expresses characteristic Phanerozoic zircon age signatures associated with source regions in eastern Australia that are interpreted to reflect inversion in the Ceduna Sub-basin to the east. Detrital zircon signatures in Plio-Pleistocene palaeoshoreline sediment are also relatively distinct, indicating derivation from coastal erosion in the Leeuwin Complex (~0.5 and 0.7 Ga subchondritic grains) and Albany-Fraser Orogen (~1.2 Ga subchondritic grains) several hundred, to over a thousand kilometers to the west. Collectively, results highlight the fundamental geological processes associated with rifting that dramatically change the character of sediment provenance via (a) isolation of pre-existing primary and secondary sources of detritus, (b) development of new source regions in basin compartmentalized highs and localized fault scarps, and (c) establishment of marine and coastal currents that redefine clastic sediment transport.

Resolving the Paleogeographic Puzzle of the Lhasa Terrane in Southern Tibet

“…This link coincides with data on the Paleozoic and Mesozoic sedimentary sequences in Western Australia (Morón et al, 2019). These data reveal the development of similar transport pathways for glaciers and rivers commencing from headwaters in Antarctica and central Australia, flowing northward across the Perth and Canning Basins, and finally debouching on the margin of the Paleo-Tethys Ocean (Barham & Kirkland, 2020;Morón et al, 2019) (Figure 6). These transport pathways make it possible to deposit the Lhasa PCGDs and Paleozoic metasedimentary rocks (Zhu et al, 2011) that both originated from sources in Antarctica and central Australia (Figure 6).…”

“…Reconstruction of eastern Gondwana during the Permo-Carboniferous showing the paleogeographic locations of the Lhasa Terrane and Southern Qiangtang (basemap is from Scotese, 2012). Blue and yellow solid lines show the proposed main sediment transport pathways with headwaters in interior India, Antarctica, and central Australia, finally debouching on the margin of the Paleo-Tethys Ocean(Barham & Kirkland, 2020;Morón et al, 2019; this study). The extents of ice sheets and diamictites are fromAudley-Charles (1988).…”

Reorganization of continent‐scale sediment routing based on detrital zircon and rutile multi‐proxy analysis

“…Thus, crustal‐ to mantle‐scale processes, such as tectonic deformation (e.g., Castelltort et al, 2012; Clark et al, 2004; Olierook et al, 2019), mantle hotspots (Chardon et al, 2016) and mantle convection (Faccenna et al, 2019) are first‐order controls of erosional activity and the spatiotemporal evolution of drainage patterns. These external factors may control lifespans of sediment pathways that can persist for several 100 s of Myr (e.g., Morón et al, 2019; Prokopiev et al, 2008), but can also drive significant reorganization or fragmentation of sediment routing systems over different timescales and can leave characteristic imprints on the detrital record (e.g., Barham & Kirkland, 2020; Blum & Pecha, 2014; Song et al, 2022; Tyrrell et al, 2007). Therefore, studying variations of sedimentary compositions within basins can inform the co‐evolution of drainage pattern and their controls (e.g., Davis et al, 2010; Zhang et al, 2019).…”

“…Hence, a robust source discrimination, capable of disentangling various non‐distinctive source signals, demands a multi‐proxy approach. Lu–Hf isotope geochemistry, sensitive to the source of the melt in which the zircon crystallized, has been utilized to improve the interpretation of sediment source terranes (e.g., Barham & Kirkland, 2020; Ustaömer et al, 2016; Veevers et al, 2005). The 176 Hf/ 177 Hf ratio that is commonly expressed using the epsilon notation (εHf; deviation from the chondritic Hf ratio), can inform about the tectonic setting of zircon formation (e.g., Belousova et al, 2010; Collins et al, 2011).…”