In situ Rb–Sr dating and REE analysis of glauconites and detrital feldspars from the Ediacaran/Cambrian strata: Centralian and Adelaide Superbasins, Australia

Proterozoic sedimentary rocks are challenging to date due to the absence of fossils for biostratigraphic constraints. This study employs in situ Rb–Sr dating of K-rich minerals (glauconite and K-feldspar) to constrain depositional and diagenetic histories within the late Proterozoic–early Paleozoic Centralian and Adelaide Superbasins, Australia. Samples analyzed include the Arumbera Sandstone (Amadeus Basin), Dey Dey Mudstone (Officer Basin), and Wonoka Formation (Flinders Ranges), spanning the Precambrian-Cambrian transition (∼580–520 Ma). 

In situ Rb–Sr dating of glauconite from the above depositional systems yielded ages between 422 ± 11 Ma and 472 ± 5 Ma, thus systematically younger than the expected depositional ages, reflecting diagenetic overprinting during later post-depositional tectonic events, such as the Alice Springs Orogeny (Rodingan Event, ∼440–430 Ma) (Scrimgeour, 2013), and the Delamerian Orogeny (∼514–480 Ma). Interestingly, a pore-filling K-rich clay material from the Arumbera Sandstone (Amadeus Basin) returned an age of 530 ± 67 Ma, aligning with the expected depositional age. 

Finally, detrital K-feldspar grains from the Arumbera Sandstone provided older Rb–Sr ages (1149–1780 Ma), which are thus consistent with ages or possible source rocks from the Musgrave Province and Kimban Orogen, supported by petrographic analysis as well as distinct REE patterns. These findings demonstrate the utility of combined in situ Rb–Sr dating, petrographic and REE analyses, for investigating diagenetic processes, post-depositional tectonic events, and sediment provenance in the Proterozoic basins. This novel approach offers a direct, rapid, efficient geochronological tool for characterizing complex depositional, diagenetic and alteration/burial histories of glauconite-rich strata with minimal sample preparation.