Sedimentology and stratigraphy of the Mesoproterozoic Elwin Subgroup (Aqigilik and Sinasiuvik formations), uppermost Bylot Supergroup, Borden Rift Basin, northern Baffin Island

Abstract

The Elwin Formation of the Mesoproterozoic Nunatsiaq Group is renamed Elwin Subgroup with two intergradational formations of similar thickness named Aqigilik and the overlying Sinasiuvik. The Elwin Subgroup marks an abrupt change in basin dynamics from regional faulting, which accompanied deposition of immediately underlying rocks during closing of the Mesoproterozoic Poseidon Ocean, to regional warping of a mature stable shelf. Strata consist of at least 890 m of unmetamorphosed laminated to thick bedded and massive, varicoloured sandstones, siltstones, shales, and minor carbonate rocks. The Aqigilik Formation contains five members and the Sinasiuvik, three. Subdivision is based on the arrangement of lithofacies that represent: 1)braidplain, 2) shoreface, 3) backshore-lagoon, and 4) shallow shelf environments. Basal Aqigilik Formation shallow marine deposits underlie a northeast prograding tongue of sheetflood-dominated, braidplain deposits. The braidplain grades laterally into, and is overlain by intertidal deposits, succeeded by backshore and lagoonal, and by shallow-shelf and shoreline deposits. Paleocurrents indicate west to southwest sources. Sinasiuvik strata were deposited on a siliciclastic shelf of a subsiding basin. Each member of the formation consists of a fining- and thinning-upwards transgressive cycle capped by a thicker coarsening- and thickening-upwards shoaling cycle. These members reflect overall deepening and stabilization of the shelf. Paleocurrent directions range from east (base) to northwest (top) and indicate a more northerly transport direction in comparison to the Aqigilik Formation directions. A semi-arid to arid climate is indicated by the presence of evaporite mineral pseudomorphs, ephemeral stream deposits, and stromatolitic dolostones. Paleomagnetic data suggest deposition in a northern tropical region.

δ<SUP>13</SUP>C stratigraphy of the Proterozoic Bylot Supergroup, Baffin Island, Canada: implications for regional lithostratigraphic correlations

“…Nauyat basalts yielded a paleomagnetic pole identical to that of Mackenzie intrusions (Fahrig et al 1981) which elsewhere give an age of 1267 ± 2 Ma (U-Pb baddeleyite; LeCheminant and Heaman 1989). This date, broadly supported by Rb-Sr (1129 Ma, no error reported; Knight and Jackson 1994) and K-Ar ages (ranging from 762 ± 26 to 1221 ± 31 Ma; Jackson 1974;Jackson and Iannelli 1981) on Nauyat Formation basalts, provides an approximate age for initiation of Bylot sedimentation. Somewhat younger radiometric ages obtained from the Nauyat basalts may be related to regional greenschist stage metamorphism (Jackson et al 1990).…”

“…The similarity of Strathcona Sound paleomagnetic poles both to those of the Nauyat Formation and to the well-constrained Logan Sill pole (1109 2 4 − + Ma, U-Pb baddeleyite; Krogh et al 1987), however, suggests that the Bylot Supergroup may have been deposited wholly within the Mesoproterozoic (Fahrig et al 1981;Knight and Jackson 1994). If these estimates are correct, it is unlikely that Bylot Supergroup deposition was coeval with that of the Shaler Supergroup and correlatives of Sequence B, which have maximum ages between 1077 ± 3 and 1003 ± 3 Ma (U-Pb detrital zircon; Rainbird et al 1996).…”

“…Carbonate rocks unconformably overlie fluvial to marine volcanic and siliciclastic rocks of the Eqalulik Group and interfinger with (Athole Point) or are unconformably overlain by (Victor Bay) subtidal marine sandstone, silt, and shale of the Nunatsiaq Group (Jackson and Iannelli 1981). For detailed descriptions of Bylot Supergroup siliciclastic rocks, refer to Iannelli (1979), Jackson and Iannelli (1981), Jackson et al (1975), and Knight and Jackson (1994).…”

Late Mesoproterozoic rifting in Arctic Canada during Rodinia assembly: impactogens, trans‐continental far‐field stress and zinc mineralisation

“…K). The basin floor was palaeotopographically complex owing to faulting (Jackson and Iannelli, ; Knight and Jackson, ). The Strathcona Sound Formation generally consists of deep‐water redbeds that coarsen and shallow upward, becoming dark green‐grey (Fig.…”

Mesoproterozoic deep‐water reefs from Borden Peninsula, Arctic Canada

“…Borden Basin is a 250-km-long graben that contains a 10-km-thick succession of virtually unmetamorphosed and undeformed strata ranging in age from Proterozoic to Tertiary (Jackson & Sangster, 1987). The Proterozoic geology has been summarized by Lemon & Blackadar (1963), Blackadar (1970), Geldsetzer (1973), Jackson & Ianelli (1981 and Knight & Jackson (1994) ; Hofmann & Jackson (1991 have described the microfossils. Proterozoic strata comprise the Bylot Supergroup, which can be subdivided into three groups that reflect different tectonic regimes: the Eqalulik Group comprises volcanics and siliciclastic sediments deposited during early stages of rifting, the Uluksan Group contains carbonates deposited during a period of relative tectonic stability and the Nunatsiaq Group comprises mainly siliciclastic deposits that reflect renewed tectonic activity (Fig.…”