The Mount Bruce Supergroup of Western Australia records an almost uninterrupted stratigraphic succession from c. 2780 Ma to ≥2208 Ma that includes Huronian-aged diamictites in its upper part, as well as physical and geochemical proxy records of the closely associated Great Oxidation Event (GOE). Until recently, this succession was considered to contain a single glacigenic horizon of uncertain absolute age. Global correlation with the Huronian Glacial Event (HGE) is complicated by the existence of three to four glacigenic horizons in the type area in North America, and in Southern Africa. The accuracy of such correlations is critical to establishing a Proterozoic chronostratigraphic Global Stratotype Section and Point (GSSP), based on the first appearance of glacial deposits (Van Kranendonk et al., 2012; Shields et al., 2022). The Mount Bruce Supergroup also contains a well-known proxy record of the ocean-atmosphere system prior to the GOE, as preserved in the BIFs and shales of the Hamersley Group, as well as the current chronometric Archean–Proterozoic boundary, and is therefore of global significance to definition of this boundary and associated chronostratigraphic units. This poster summarizes recent work aimed at refining and formalizing the stratigraphy of intervals likely to contain Paleoproterozoic GSSP candidates. Significant new observations include basal Boolgeeda Iron Formation and Turee Creek Group disconformities, as well as eight unconformity-bound depositional units in the revised Turee Creek Basin, identification and naming of four diamictites of interpreted glacigenic origin, revision of the stratigraphic nomenclature of the Wyloo Group, and confirmation of the genetic relationship between the Cheela Springs Basalt and the newly named c. 2208 Ma Balgara Dolerite. These new observations and geochronological constraints are particularly helpful in constraining correlations to Southern Africa. A significant advantage of the relatively continuous Australian stratigraphic record of the Archean–Proterozoic transition, over that of North America or Southern Africa, is that it is preserved in a coherent geographical area without uncertainties in regional correlation. However, more work on geochronological constraints and the geochemical proxy record is required within this succession in order to better constrain potential GSSPs.

Reference(s)

Shields, GA, Strachan, RA, Porter, SM, Halverson, GP, Macdonald, FA, Plumb, KA, Alvarenga, CJ de, Banerjee, DM, Bekker, A, Bleeker, W, Brasier, A, Chakraborty, PP, Collins, AS, Condie, K, Das, K, Evans, DAD, Ernst, R, Fallick, AE, Frimmel, H, Fuck, R, Hoffman, PF, Kamber, BS, Kuznetsov, AB, Mitchell, RN, Poiré, DG, Poulton, SW, Riding, R, Sharma, M, Storey, C, Stueeken, E, Tostevin, R, Turner, E, Xiao, S, Zhang, S, Zhou, Y and Zhu, M 2022, A template for an improved rock-based subdivision of the pre-Cryogenian timescale: Journal of the Geological Society, v. 179, no. 1, article no. jgs2020-222, doi:10.1144/jgs2020-222.

Van Kranendonk, MJ, Altermann, W, Beard, BL, Hoffman, PF, Johnson, CM, Kasting, JF, Melezhik Victor A., Nutman, AP, Papineau, D and Pirajno, F 2012, Chapter 16 - A chronostraigraphic division of the Precambrian: Possibilities and challenges, in The geologic time scale edited by FM Gradstein, JG Ogg, MD Schmitz and GM Ogg: Elsevier 16, p. 299-392.