The G?adalupian (Permian) Kamura event in European Tethys

摘要

In order to document paleoenvironmental conditions of the equatorial western Paleo-Tethys during the late Middle Permian prior to the end-G?adalupian mass extinction, chemostratigraphic analysis using stable carbon isotopes was conducted for the G?adalupian rocks at Brusane in the Velebit Mtn., central Croatia. By analyzing 72 carbonate samples of the Capitanian (Upper G?adalupian) Velebit Formation, we found an interval with unusually high δ~(13)C_(carb) values (+4 to +6‰) in the ca. 150m-thick Yabeina (fusuline) Zone. The present find clarifies that the primary productivity and burial rate into the sediments were considerably high during the Capitanian in westernmost Paleo-Tethys. This chemostratigraphic signal is properly correlated with the "Kamura event" detected in a mid-Panthalassan paleo-atoll limestone in Japan. The present results identify the Capitanian "Kamura event" for the first time in European Paleo-Tethys on the opposite side of the globe from the mid-Panthalassan paleo-seamount, and prove the global context of the event as well as its utility in chemostratigraphic correlation. In order to enhance bioproductivity on a global scale, the increase in nutrient supply is inevitable. In addition to riverine run-off from Pangea, active oceanic circulation, in particular upwelling of deep-sea water enriched in nutrients, was likely vital both in Panthalassa and Paleo-Tethys. The extinction of some G?adalupian fauna, in particular photosymbiotic community (large-tested fusulines, large bivalves, rugose corals), was likely related to a temporary cooling coupled with eutrophication in low-latitude shallow marine environments of Paleo-Tethys and Panthalassa.