Carboniferous isotope stratigraphy

Abstract

AbstractWe present an updated set of Carboniferous Sr, C and O isotope stratigraphies based on the existing literature, given the importance of chemostratigraphy for stratigraphic correlation in the Carboniferous. The Carboniferous 87Sr/86Sr record, constructed using brachiopods and conodonts, exhibits five first-order phases beginning with a rapid decline from a peak value of c. 0.70840 at the Devonian–Carboniferous boundary to a trough (0.70776–0.70771) in the Visean followed by a rise to a plateau (c. 0.70827) in the upper Bashkirian. A decline to c. 0.70804 follows from the lowermost Gzhelian to the close of the Carboniferous. Contemporaneous carbonate δ13C records exhibit considerable variability between materials analysed and by region, although pronounced excursions (e.g. the mid-Tournaisian positive excursion and the end-Kasimovian negative excursion) are present in most records. Bulk carbonate δ13C records from South China and Europe, however, are generally consistent with those of brachiopod calcite from North America in terms of both absolute values and trends. Both brachiopod calcite and conodont phosphate δ18O document large regional variability, confirming that Carboniferous δ18O records are invalid for precise stratigraphic correlation. Nevertheless, significant positive δ18O shifts in certain intervals (e.g. mid-Tournaisian and the Mississippian–Pennsylvanian transition) can be used for global correlation.