Sedimentology and stratigraphy of eastern and central Belcher Islands, Northwest Territories.

Abstract

Red 5 grey cross-bedded arkoses, mudstones, OMAROLLUK 2105 m Well-bedded greywackes and-shales, typical Bouma cycles. Minor flat pebble conglomerates filling channels. Dewatering structures, concretions. 8 Northern Belcher Is. <5 Bakers Dozen Is. c^3Loaf Is. <? Twin Cairns Is. Tukarak Is. 3)7 Laddie Hbr Figure 3. Map showing station numbers and locations of sections measured.

A productivity collapse to end Earth’s Great Oxidation

“…The Costello Formation is the dominant host of barites (and Ba and SO 4 ) in the Belcher Group and we explore hypotheses for their genetic origin here. There is no stratigraphic, sedimentologic, mineralogic, or petrographic evidence for subaerial exposure in the Costello Formation (20)(21)(22), and thus it is unlikely that the macrobarites formed via direct precipitation of Ba-and SO 4 -bearing salts in a strongly evaporitic environment. Rather, their large size, well-developed crystal habit, and lack of preferred orientation with respect to bedding strongly suggest that these barites formed postdepositionally rather than in the water column or at the sediment-water interface with coeval carbonates (Fig.…”

“…1). There is no evidence for subaerial exposure or the presence of a strongly evaporitic/restricted environment associated with the Costello Formation barites; to the contrary, slumps and partial Bouma sequences have led to the interpretation that the Costello Formation was deposited in a foreslope environment (21). the stratosphere involving the production of O 3 (ozone) do so with a mass-independent partitioning of isotopes, where O 3 becomes enriched in 17 , rendering residual dissolved Ba enriched in "heavy" Ba isotopes by a corresponding amount.…”

“…The overlying Flaherty Formation is composed of submarine basalt and is up to several kilometers thick. The Belcher Group concludes with the deposition of a flysch (Omarolluk Formation) and molasse [Loaf Formation (20)(21)(22)].…”

Organic diagenesis in stromatolitic dolomite and chert from the late Palaeoproterozoic McLeary Formation

“…Uranium-lead dating on zircons carried out by Hodgkiss et al (2019) shows that the maximum age of the Belcher Group is 2.0185 ± 0.001 Ga (obtained from tuff in the Kasegalik Formation), and the minimum age is 1.8542 ± 0.001 Ga (obtained from the contact between the Flaherty and Omarolluk Formations). The 14 formations of the Belcher Group, including two volcanic units, have a total thickness of 7000-9000 m (Figure 1B; Ricketts, 1979)…”

“…These units were deposited during four megacycles that represent changes in the depositional environment (Ricketts, 1979). During the first megacycle, over a kilometre of carbonates and mudstones of the Kasegalik Formation was deposited in a supratidal environment on a marine platform.…”