87Sr/86Sr evidence from the epeiric Martin Ridge Basin for enhanced carbonate weathering during the Hirnantian.

ABSTRACT: A pronounced positive ?13C excursion in the Hirnantian Age has been documented globally, reflecting large perturbations of carbon cycling in the Late Ordovician oceans. Increased organic-carbon burial or enhanced carbonate weathering during glacioeustatic sea-level regression has been proposed to account for this anomalous C-isotope excursion. To test the two competing hypotheses, we measured 87Sr/86Sr and ?13C of carbonates from the Copenhagen Canyon section in Nevada, USA. Our data reveal two rapid negative 87Sr/86Sr shifts that coincide with two prominent positive ?13C excursions and glacial advances. Numerical model simulations suggest that enhanced weathering of carbonates driven by glacio-eustatically controlled sea-level fall is required to produce the observed drops of 87Sr/86Sr and the coeval large positive ?13C excursions, possibly with or without increased organic carbon burial.

SUBMITTER: Hu D 

PROVIDER: S-EPMC5595791 | biostudies-other | 2017 Sep

REPOSITORIES: biostudies-other