High-resolution correlation between contrasting early Tonian carbonate successions in NW Canada highlights pronounced global carbon isotope variations

Abstract

Carbonate successions older than the 800 Ma Bitter Springs isotope anomaly are sparse and this time is consequently poorly understood. The Shaler and Mackenzie Mountains supergroups of northwestern Canada, however, contain thick ca. 1050–750 Ma carbonate successions recording both deep- and shallow-water depositional environments that are interpreted to have been deposited in two separate, extensive epicratonic basins on the Rodinia supercontinent. When the contrasting sedimentology (benthic- versus pelagic-dominated carbonate production) and basin dynamics of two correlative carbonate successions from these basins are accounted for, a precise regional correlation can be made using sequence stratigraphic and carbon isotope data. This paper presents a regionally correlatable carbon isotope profile, containing substantial excursions between −2 and 7‰vpdb, that can be used to extend the global curve into early Neoproterozoic time prior to the Bitter Springs anomaly.