GSA Annual Meeting in Indianapolis, Indiana, USA - 2018

Paper No. 283-1
Presentation Time: 1:30 PM


MONTAÑEZ, Isabel P.1, OSLEGER, Dillon J.2, CHEN, Jitao3, WORTHAM, Barbara E.1, STAMM, Robert G.4, NEMYROVSKA, Tamara I.5, GRIFFIN, Julie M.6, POLETAEV, Vladislav I.5 and WARDLAW, Bruce R.4, (1)Department of Earth and Planetary Sciences, University of California, Davis, One Shields Dr., Davis, CA 95616, (2)Department of Earth Science, University of California Santa Barbara, Santa Barbara, CA 93101, (3)CAS Key Laboratory of Economic Stratigraphy and Palaeogeography, Nanjing Institute of Geology and Palaeontology and Center for Excellence in Life and Paleoenvironment, Chinese Academy of Sciences, Nanjing, 210008, China, (4)U.S. Geological Survey, Eastern Geology and Paleoclimate Science Center, Reston, VA 20192, (5)Institute of Geological Sciences, National Academy of Sciences of Ukraine, O. Gonchar Street, 55-b, Kiev, 052054, Ukraine, (6)Geology Department, California State University Sacramento, 6000 J Street, Sacramento, CA 95819

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 δ18OPO4 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 δ18OPO4 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 δ18OPO4 record from South China and from the global seawater Sr isotope trend.

An up to 6‰ negative offset in Donets δ18OPO4 values from those of more open-water conodonts and greater temporal variability in δ18OPO4 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 δ18OPO4 and 87Sr/86Sr values as proxies of paleo-seawater composition, sea-surface temperatures, and magnitudes of glacioeustasy.