CHARACTERISTICS AND COMPARISON OF THE BASAL PALEOPROTEROZOIC COVER SEQUENCE OF THE SUPERIOR AND WESTERN CHURCHILL PROVINCES OF LAURENTIA

Recent sequence stratigraphic studies in concert with U-Pb dating have helped to further our understanding of the temporal relationships among some of the Earth’s oldest thick, mature, cratonic sedimentary successions This information is critical for inter-cratonic correlations and for evaluating paleocontinental reconstructions. In North America, the southern Superior Province (Southern Province), and the western Churchill Province, in the region straddling the northern end of the Rae-Hearne domain boundary, preserve thick early Paleoproterozoic cover successions. In the Southern Province, the cover sequence comprises from west to east, Animikie Group, Marquette Range Supergroup, Huronian Supergroup-Whitewater Group and Mistassini-Otish Mountains Group. In the western Churchill, the sequence comprises Hurwitz-Kiyuk Group, Amer, Ketyet River, Penrhyn, Piling and Lake Harbour groups. Glacial diamictites characterize the Southern Province sequence but are notably absent from the western Churchill sequences, except for the Hurwitz Group (Padlei Fm), which is the only one lying on the Hearne domain. This calls into question previous correlations between the lower parts of sequences deposited on the Rae and those on the Hearne and Southern provinces, and suggests that the Rae and Hearne were not connected until deposition of the thick quartzarenites, which mark the base of the Rae province cover sequences. All of the successions are characterized by deep-water marine deposits ± Fe-formation ± mafic volcanic rocks above the quartzarenites, although those of the Hurwitz Group are >150 Ma older. Above the deep-water deposits in the Rae domain and Southern province sequences is a ca. 1.95-1.85 Ga upward-coarsening succession interpreted to represent a foredeep, formed during collisional orogenesis attending amalgamation of Laurentia. Although lithostratigraphic correlations indicate a similar sedimentary succession and evolution for the trailing margins of the Superior Province and Rae domain it is unlikely that these margins were linked or that they evolved at the same time. Further geochronology is required, but it is more likely that the processes of continental collision and assembly were diachronous.