STABLE AND RADIOGENIC STRONTIUM ISOTOPE (δ88SR, 87SR /86SR) IN SEAWATER ACROSS GUADALUPIAN-LOPINGIAN BOUNDARY (PERMIAN)

In order to reconstruct the secular change in stable and radiogenic strontium isotope ratios of Permian seawater, we analyzed mid-oceanic paleo-atoll and shelf limestones that span across the Guadlupian-Lopingian boundary; i.e. at the Akasaka section in Japan deposited on a mid-Panthalassan paleo-seamount at 12 degree South, and at the Lianshan section in S. China deposited on a carbonate platform on the equatorial eastern Tethys. Stable strontium isotope ratios (δ⁸⁸Sr) of the Capitanian (late Guadalupian) to Wuchiapingian (early Lopingian) carbonates were measured by TRITON TIMS, by correcting isotope fractionation during mass spectrometry with ⁸⁷Sr-⁸⁴double spike. The newly obtained δ⁸⁸Sr profile of Middle-Late Permian seawater shows an interval of lowδ⁸⁸Sr values throughout the Capitanian, which is followed by a rapid increase across the G-L boundary. This profile is positively correlated with that of ⁸⁷Sr/⁸⁶Sr ratio, suggesting a sharp change in balance between carbonate burial flux and carbonate dissolution flux across the G-L boundary. The Capitanian minimum in seawater ⁸⁷Sr/⁸⁶Sr and the following rapid increase was likely driven by a major change in erosion/weathering of continental crusts probably in relation with global glaciation/deglaciation.