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

Abstract

Abstract:The Bylot Supergroup, northern Baffin Island, contains >1500 m of platform, shelf, and slope carbonates deposited between -1270 and -723 Ma. Limited chronostratigraphic data have led to the broad correlation of the Bylot Supergroup with predominantly Neoproterozoic successions in northern and western Laurentia; yet, detailed correlation has been impossible given biostratigraphic and lithostratigraphic limitations. Carbon-isotope chemostratigraphy represents a potential dataset to constrain such interregional correlations. Carbon isotopic data from the Bylot Supergroup and broadly coeval successions from Somerset Island and northwest Greenland reveal distinct stratigraphic trends in δ 13 C, with intervals of moderate 13 C enrichment (+3.5 ± 1‰) punctuated by excursions to slightly negative values (-1.0 ± 1‰). Although the scale of the observed variation is muted relative to Neoproterozoic standards, the dissimilarity of values to those recorded in northwestern Laurentia suggests that these strata delineate a discrete depositional interval. Comparison of isotopic values with published data indicates that δ 13 C values between approximately -1.0 and +4.0‰ are characteristic of the interval between -1300 and -800 Ma. This pattern is distinct from that of younger Neoproterozoic successions, which typically record values >+5‰, and older Mesoproterozoic successions, which record values near 0‰, and suggests that these moderately positive values may be useful for broad time correlation. Compilation of new and published data permits the tentative reconstruction of a global Mesoproterozoic carbon isotopic curve.Résumé : Le Supergroupe de Bylot, dans le nord de l'île de Baffin, est formé de >1500 m de carbonates qui furent déposés sur une plate-forme continentale et un talus, entre -1270 et -723 Ma. Les données chronostratigraphiques limitées n'autorisent qu'une corrélation d'ordre général entre le Supergroupe de Bylot et les successions principalement néoprotérozoïques des régions septentrionales et occidentales de Laurentia; jusqu'à présent, il a été impossible d'établir une corrélation détaillée en raison du petit nombre de données biostratigraphiques et lithostratigraphiques. La chimiostratigraphie des isotopes du C a fourni un ensemble de données pouvant aider à mieux définir les corrélations inter-régionales. Les résultats des analyses d'isotopes du C pour le Supergroupe de Bylot et les successions grossièrement contemporaines de l'île Somerset et du nord-ouest du Groenland révèlent des tendances stratigraphiques distinctes dans les valeurs de δ 13 C, avec des intervalles d'enrichissement modéré de 13 C (+3,5 ± 1‰), ponctués d'incursions de valeurs légèrement négatives (-1,0 ± 1‰). Même si l'échelle de la variation observée est atténuée par rapport aux standards du Néoprotérozoïque, les valeurs différentes de celles enregistrées dans le nord-ouest de Laurentia suggèrent que ces strates représentent un intervalle de sédimentation discontinue. La comparaison des données isotopiques avec celles déjà publiées in...

Carbonate rocks and related facies with vestiges of biomarkers: Clues to redox conditions in the Mesoproterozoic ocean

“…The mudstone-dominated sequences developed during transgressions when the input of terrigenous sand decreased substantially, or when the bulk of the coarser clastics were trapped in fluvial systems or in coastal areas (Catuneanu et al, 2011). Guo et al, 2013), Mauritania (Gilleaudeau et al, 2013a), and Arctic Canada (Baffin Bay and Bylot Island, Kah et al, 1999).…”

“…However, even though distal shelf and basinal settings of the Mesoproterozoic appear to have been anoxic and euxinic (Shen et al, 2002(Shen et al, , 2003Poulton et al, 2004) or ferruginous (Poulton et al, 2010;Planavsky et al, 2011;Scott et al, 2012), there is a moderate increase in biospheric oxygen variability in the late Mesoproterozoic evidenced from increased carbon isotopic variability (Frank et al, 1997(Frank et al, , 2003Kah et al, 1999), an increase in marine sulphate concentration ) from low sulphate concentrations in early Mesoproterozoic (Luo et al, 2015), the widespread appearance of marine gypsum (Kah et al, 2001, and increased oxidative sulphur cycling in marine and terrestrial environments (Johnston et al, 2005;Parnell et al, 2010). From a sedimentological point of view, the Mesoproterozoic was a time of extensive epeiric and epicratonic seas and a relative highstand of sea level, wherein thick successions of shallow-water carbonate strata were deposited in broad intracratonic basins, as in China (Guo et al, 2013;Mei and Tucker, 2013), Siberia (Bartley et al, 2001), West Africa Gilleaudeau and Kah, 2013a,b;, and the Canadian Arctic (Kah et al, 2001).…”

Covariance of Microfossil Assemblages and Microbialite Textures Across an Upper Mesoproterozoic Carbonate Platform

“…1250 Ma and older than ca. 850 Ma (Kah et al, 1999(Kah et al, , 2012, and microfossils suggest that the depositional age of Angmaat Formation strata lies closer to the lower than to the upper boundary established by regional basalts (Hofmann andJackson, 1991, 1994). Micropaleontological data on correlative successions in northwestern Greenland (Strother et al, 1983;Samuelsson et al, 1999) and Somerset Island (Butterfield, 2001) further support a late Mesoproterozoic age for Angmaat deposition.…”

“…Sedimentary rocks of the Bylot Supergroup crop out extensively within the fault-bounded Borden Basin of northern Baffin and Bylot islands ( Fig. 1; Jackson and Ianelli, 1981;Kah et al, 1999;Turner, 2009). Traditionally, deposition of a laterally extensive package of carbonatedominated strata-originally distinguished as the Society Cliffs Formation-was considered to represent a period of relative tectonic quiescence within the basin, during which sea level rise promoted an extensive, northwestward deepening carbonate ramp (Blackadar, 1956;Lemon and Blackadar, 1963;Geldsetzer, 1973).…”

“…Traditionally, deposition of a laterally extensive package of carbonatedominated strata-originally distinguished as the Society Cliffs Formation-was considered to represent a period of relative tectonic quiescence within the basin, during which sea level rise promoted an extensive, northwestward deepening carbonate ramp (Blackadar, 1956;Lemon and Blackadar, 1963;Geldsetzer, 1973). Building on the work of Jackson and Ianelli (1981), who recognized a pronounced dimimution of siliciclastic material upward in the Society Cliffs Formation, and Kah (1997Kah ( , 2000 and Kah et al (1999Kah et al ( , 2001, who recognized a distinct shift to deeper-water facies west of a persistent oolitic shoal in the region of Tremblay Sound, Turner (2009) divided the these strata into four formations (Iqqittuq, Angmaat, Nanisivik, and Ikpiarjuk) that better reflect regional lithologic trends. Here we focus on the southeastern successions of the former Society Cliffs Formation, now considered the Angmaat Formation.…”