Fig. 1: Regional geological map with sample locations and configuration of Gondwana during the Late Palaeozoic Ice Age.

a Simplified geological map of Fleurieu Peninsula, Yorke Peninsula and Kangaroo Island in South Australia^24,79,80. The geological map illustrates the extent of the Permo-Carboniferous Troubridge Basin (outlined in blue) and known paleo ice-flow indicators²⁹. The asterisk (*) indicates the detrital garnet-rich placer sand and glacial strata samples, and samples without an asterisk are local basement rocks. The garnet-rich placer deposit samples come from four beaches in South Australia: Myponga Beach (sample MYB), Petrel Cove Beach (PCB), Port Moorowie Beach (PMB) and Port Vincent Beach (PVB). The two Permo-Carboniferous glacial strata (samples BS2 and BQ7) are from the Cape Jervis Formation on Kangaroo Island, which locally also contains detrital garnet⁴¹. Additionally, three basement samples were analysed to define regional garnet populations: a Barossa Complex granulite from the Myponga Inlier in the Adelaide Hills (MYPINL), a Delamerian metapelite from Harrogate (171–71) and a Delamerian pegmatite from Vivonne Bay (VIV). b Plate tectonic reconstruction of Gondwana during the Permo-Carboniferous glaciation (glaciation maximum; Pennsylvanian–Early Permian). The base map shows the location of the continents in the supercontinent configuration at ~300 Ma⁸¹ and the areas of ice sheet extent (with ice-flow directions)^29,39.