The upper Precambrian succession of the southern tip of Banks Island comprises about 900 m of sedimentary rocks intruded by thick gabbro sills. The lowest unit exposed is a cherty stromatolitic carbonate. This is overlain by a thicker unit of sandstones and mudstones. Most of the sequence is considered to be correlative with the Glenelg Formation, which is the basal formation of the late Precambrian Shaler Group of the Minto Arch on Victoria Island. A thick shale unit at the top of the Banks Island Precambrian succession may be correlative with the basal part of the Reynolds Point Formation on Victoria Island.Paleocurrent measurements from the Banks Island rocks indicate transport essentially to the northwest. An abundantly cross-bedded sandy limestone unit in the upper part of the Reynolds Point Formation in the Minto Inlet area of Victoria Island gives a polymodal paleocurrent pattern. This unit was probably deposited in a shallow marine environment under tidal influence. Tidalites have been recognized in the lower clastic unit of the Reynolds Point Formation at several localities in the Minto Arch. Stromatolites form the lower part of the Shaler Group suggest that these rocks are early Upper Riphean (latest Helikian to early Hadrynian). The stromatolite forms appear to occur in a non-repetitive sequence that provides a powerful means of intrabasinal correlation.The depositional area is envisaged as a large embayment of the sea, comparable in scale, shape, and sedimentary fill, to the younger Michigan Basin. The northwest margin of the basin is tentatively interpreted as a breached arch, shedding terrigenous clastics to the NW in the Banks Island area, and to the east at the north end of the Minto Arch. Northeasterly elongation of stromatolites in the upper Glenelg Formation at the north end of the Minto Arch may reflect tidal currents. Circulation in the basin became progressively restricted, culminating in deposition of the evaporite-bearing sequence of the upper part of the Shaler Group.

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