Paleoproterozoic Huronian basin: product of a Wilson cycle punctuated by glaciations and a meteorite impact

The Huronian Supergroup (similar to2.4-2.2 Ga) comprises up to 12 km of mai nly sedimentary supracrustal rocks. The oldest Huronian unit, the Livingsto ne Creek Formation, is chemically and mineralogically immature. Significant chemical weathering and deposition of U-rich quartz pebble conglomerates f ollowed deposition of the Livingstone Creek Formation and extrusion of the overlying, rift-related lavas of the Thessalon Formation. Much of the succe eding Huronian comprises climatically(?)-controlled tripartite cycles, each of which begins with glaciogenic diamictites, followed by mudstones and cr oss bedded arenaceous units. Huronian deposition is interpreted as the resu lt of a partial Wilson cycle, involving rifting and development of a southw ard-facing passive margin. The similar to2.4 Ga Murray and Creighton granit es have been considered by others to be coeval with an early orogenic episo de (Blezardian). Expected unconformities are, however, lacking and these gr anites, together with co-eval volcanic rocks and abundant soft sediment def ormation structures are considered to be due to anorogenic processes during Huronian basin subsidence. The main deformation of the Huronian is probabl y related to the Penokean orogeny (similar to1.89-1.8 Ga). Geochemical inve stigations have contributed to paleoclimatic and provenance studies and hav e helped to define basin-wide metasomatic events. A large impact at similar to1.85 Ga likely played an important role in formation of the Sudbury Igne ous Complex (SIC) and deposition of fallback breccias of the Onaping Format ion (basal Whitewater Group in the Sudbury basin). Overlying sedimentary ro cks of the Whitewater Group are considered to be a fortuitously-preserved p ortion of a widespread flysch apron that spread across the southern margin of the Superior Province as a foreland basin fill, in response to the closu re phase of the Wilson cycle during the Penokean orogeny. Geochronological data suggest that these events occurred during the Penokean orogeny. (C) 20 01 Elsevier Science B.V. All rights reserved.