EarthRef.org Reference Database (ERR) -- Kah et al. 1999

The Bylot Supergroup, northern Baffin Island, contains >1500 m of platform, shelf, and slope carbonates deposited between similar to 1270 and similar to 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 delta(13)C, With intervals of moderate C-13 enrichment (+3.5 +/- 1 parts per thousand) punctuated by excursions to slightly negative values (-1.0 +/- 1 parts per thousand). 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 delta(13)C values between approximately -1.0 and +4.0 parts per thousand are characteristic of the interval between similar to 1300 and similar to 800 Ma. This pattern is distinct from that of younger Neoproterozoic successions, which typically record values >+5 parts per thousand, and older Mesoproterozoic successions, which record values near 0 parts per thousand, 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.