CARBONIFEROUS CLIMATE TELECONNECTIONS ARCHIVED IN COUPLED BIOAPATITE δ18OPO4 AND 87SR/86SR, DONETS BASIN, UKRAINE

There is growing evidence for geographic and temporal variability in the environmental conditions of semi-restricted epicontinental seas that leads to the decoupling of their seawater isotopic signatures from those of the open ocean. Here we present conodont apatite δ¹⁸O_PO4 and ⁸⁷Sr/⁸⁶Sr records spanning 24 Myr of the Late Mississippian through Pennsylvanian derived from the U-Pb calibrated cyclothemic succession of the Donets Basin, eastern Ukraine. Systematic fluctuations in bioapatite δ¹⁸O_PO4 and ⁸⁷Sr/⁸⁶Sr broadly follow major shifts in the Donets onlap-offlap history and inferred regional climate, but are distinct from a contemporaneous more open-water δ¹⁸O_PO4 record from South China and from the global seawater Sr isotope trend.

An up to 6‰ negative offset in Donets δ¹⁸O_PO4 values from those of more open-water conodonts and greater temporal variability in δ¹⁸O_PO4 and ⁸⁷Sr/⁸⁶Sr records are interpreted to primarily record climatically driven changes in local environmental processes in the Donets sea. Systematic isotopic shifts associated with Myr-scale sea-level fluctuations, however, indicate an extrabasinal driver. We propose a mechanistic link to glacioeustasy through a teleconnection between high-latitude ice changes and atmospheric pCO₂ and regional monsoonal circulation in the Donets region. Inferred large-magnitude changes in Donets seawater salinity and temperature, not archived in the more open-water or global contemporaneous records, indicate a modification of the global climate signal in the epicontinental sea through amplification of the climate signal by local and regional environmental processes. This finding of global climate change filtered through local processes has implications for the use of conodont δ¹⁸O_PO4 and ⁸⁷Sr/⁸⁶Sr values as proxies of paleo-seawater composition, sea-surface temperatures, and magnitudes of glacioeustasy.