Fig. 2: Detrital garnet Lu–Hf geochronology.

a Combined inverse Lu–Hf isochron plot for all analysed modern beach samples from South Australia (PCB, PMB, PVB and MYB; see Fig. 1a for sample locations). b Combined inverse Lu–Hf isochron plot for the two samples from the glaciogenic Cape Jervis Formation (BQ7 and BS2). Reference Lu–Hf isochrons for the regional Barossa Complex (green isochron line) and Delamerian Orogeny (red isochron line) metamorphism were calculated based on analyses for the Myponga Inlier gneiss (sample MYPINL; ~1627 Ma; Supplementary Fig. 4a) and Kanmantoo Group metapelite (sample 171–71; ~505 Ma; Supplementary Fig. 4b), respectively. The detrital garnet ellipses in a and b represent single-grain data points with 2σ uncertainty. The ellipses were colour-coded according to their interpreted source in South Australia (Delamerian in red, Ediacaran in blue, Barossa Complex in green). The main detrital garnet population is Ediacaran in both the modern beach sand and Permo-Carboniferous glacial strata samples, suggesting that Ediacaran garnets in the modern beach sands were recycled from the Cape Jervis Formation before deposition. c Radial plot of single-grain garnet dates (modern beach sand data in red, Cape Jervis Formation data in purple), plotted against their precision as calculated by IsoplotR⁷⁵. The most radiogenic garnet grains (¹⁷⁷Hf/¹⁷⁶Hf < 1.5) produce the most precise Lu–Hf ages (as illustrated in Supplementary Fig. 5), adding more weight to garnet population identifications. d Kernel density estimate (KDE) plots of single-grain garnet dates (modern beach sand data in red, Cape Jervis Formation data in purple), compared to zircon dates (in yellow) from the same samples. The single-grain dates were calculated as 2-point isochrons and low-radiogenic garnets were filtered out using the following criteria: (1) ¹⁷⁷Hf/¹⁷⁶Hf < 3, and (2) the relative uncertainty on single-grain ages <20%. n* indicates the number of grains that remain after the application of these two filters. For the zircon U–Pb KDE plot, detrital zircon single-grain ages with discordance > ±5% were rejected. The detrital garnet Lu–Hf isotopic data was plotted using IsoplotR⁷⁵, and this figure shows how each plot (isochron, KDE and radial) is able to detect the three distinct detrital garnet populations (Palaeo-Mesoproterozoic in green, Ediacaran in blue and Cambrian in red). The individual isochron and KDE plots for each detrital garnet sample can be found in Supplementary Fig. 3.