The Middle-Late Permian Sr-Isotope Curve and Capitanian Sr Minimum Detected in the mid-Superoceanic Paleo-Atoll Carbonates in Japan

From a mid-superoceanic paleo-atoll carbonates, a detailed secular change of the Middle-Late Permian seawater 87Sr/86Sr ratio was first analyzed. The study section of mid-oceanic paleo-atoll limestone, contained in the Jurassic accretionary complex in Kyushu (Japan), spans across the Guadalupian-Lopingian boundary (G-LB), or Middle-Upper Permian boundary, characterized by a major biotic crisis. The measured 87Sr/86Sr values vary in 0.706915-0.707561, relatively lower than the Paleozoic values previously reported. An interval with extremely low 87Sr/86Sr value was detected in the Yabeina (fusuline) Zone and Lepidolina Zone (upper lower to lower middle Capitanian, Upper Guadalupian). This extremely low 87Sr/86Sr interval is correlated with the Paleozoic minimum recognized in the stratotype Guadalupian carbonates in West Texas (around 0.70690) that were deposited on the western Pangean margin. This find not merely confirms the global chemostratigraphic utility of the 87Sr/86Sr minimum of the Capitanian, but also suggests that the oceanic chemistry at least that related to Sr isotope fluxes changed its general trend from a long-term decrease to an increase during the Capitanian, immediately before the G-LB extinction event, and considerably prior to the terminal Permian (P-TB) extinction event. A significant change in oceanic circulation system may have occurred during the Capitanian that may have brought biospheric perturbation of the G-LB event.