Stratigraphy and Sedimentology of the Paleoproterozoic Thluicho Lake Group, Southwestern Rae Province, Canada: Alluvial Basin Development in the Hinterland of the Taltson Orogen

The Thluicho Lake Group is a middle-Paleoproterozoic succession of greenschist-facies continental clastic rocks that was deposited on variably mylonitized crystalline basement rocks in the southwestern Rae Province of the Canadian Shield, near the end of 2.02-1.92-Ga Thelon-Taltson orogenesis. Two informal formations are proposed for this fining-upward succession. The Powder Lake formation comprises predominantly coarse-grained rocks including conglomerate (Gulo Lake member), pebbly sandstone (Camel Lake member), and sandstone (Wellington Lake member), whereas the overlying Camsell Portage formation consists of sandstone to siltstone (Falls member), rhythmic sandstone and argillite (Waterloo Lake member), and argillite (Slate Island member). The two informal formations represent two principal facies associations: a lower conglomerate-sandstone facies association representing an alluvial fan to distal braided plain that underwent episodic flash flooding events and an upper sandstone siltstone-mudstone facies association representing a lacustrine environment. The Thluicho Lake basins are interpreted to have been symmetrical and elongate, and are broadly parallel to older, west-to northwest-trending basement structures. Transverse alluvial fans and braided rivers and/or fan deltas developed on elevated basin margins and drained into a large perennial lake. Similarities in lithology, age, and provenance suggest that the Thluicho Lake Group may correlate with the more extensive Nonacho Group to the north. Both groups represent remnants of a strike-slip and intermontane basin system that formed in the hinterland of the Taltson orogen at ca. 1.92 Ga.