δ13C stratigraphy of the Proterozoic Bylot Supergroup, Baffin Island, Canada: implications for regional lithostratigraphic correlations

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 δ13C, with intervals of moderate 13C 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 δ13C 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.