INVITED: CORRELATION OF PALEOPROTEROZOIC GLACIAL DEPOSITS: EVIDENCE FOR THREE GLOBAL GLACIATIONS BETWEEN 2.4 AND 2.22 GA

Paleoproterozoic glacial deposits are present in North America, Fennoscandia, Western Australia, and South Africa. All these deposits are constrained in age from 2.45 to 2.22 Ga. Three glacial horizons are preserved only in the Huronian Supergroup, ON, Canada and in the Snowy Pass Supergroup, WY, USA. All other basins contain evidence either for two (South Africa) or one (Fennoscandia, Western Australia, and some basins of North America) glaciations. North American and Fennoscandian glacial deposits were convincingly correlated based on lithostratigraphy, in particular the presence of deeply weathered oxygenated horizon, mature quartzites, carbonates with highly positive carbon isotope values, and 2.22 Ga dikes and plateau basalts above the youngest Paleoproterozoic glacial diamictite. In addition to glacial diamictites, other correlative horizons in the early Paleoproterozoic basins of the northern hemisphere include basal siliciclastic rift sequence with bimodal volcanics and detrital uraninite and pyrite grains and cap carbonate with negative carbon isotope values immediately above the middle glacial horizon. Correlation with the Western Australian and South African Paleoproterozoic diamictites is more ambiguous. The oldest Paleoproterozoic glacial diamictite in South Africa is overlain by ca. 2.32 Ga carbonates with negative carbon isotope values and sits unconformably above the ca. 2.47 Ga BIFs while the youngest glacial diamictite is overlain by ca. 2.22 Ga plateau basalts, deeply weathered oxygenated horizon, mature quartzites, Al-rich shales, and carbonates with positive carbon isotope values. The South African glacial diamictites are likely correlative with the middle and upper diamictites of the Huronian Supergoup. Paleoproterozoic glacial diamictite of Western Australia sits in conformable position above 2.47-2.45 Ga BIFs, carbonates stratigraphically higher in section have normal carbon isotope values, and the succession is unconformably truncated at the top. The glacial diamictite is likely correlative with the oldest glacial diamictite of the Huronian Supergroup. Both older and younger rocks from these basins indicate low paleolatitude position which along with the extensive distribution of glacial deposits argues for global glaciations in the Paleoproterozoic.