THE LATE GUADALUPIAN KAMURA EVENT: COOLING IN THE TROPICS AND END OF GIGANTISM

The Permo-Triassic shallow marine paleo-atoll carbonates in Japan were derived from ancient seamount complexes primarily located in mid-Panthalassa, and some of such exotic limestone blocks preserve an interval from the Capitanian (Upper Guadalupian) to Wuchiapingian (Lower Lopingian). The Capitanian part (the Neoschwagerina and Yabeina-Lepidolina Zone) is characterized by abundant large-tested fusulines (Verbeekinidae, Schwagerinidae), rugose corals (Waagenophyllidae), and large bivalves (Alatoconchidae), while the Wuchiapingian part solely by small-tested fusulines (Ozawainellidae, Staffellidae, Schubertidae). The extinction and/or decline in diversity of the Guadalupian fusulines and bivalves indicate the appearance of a strong environmental stress(es) across the G-L boundary, with a clear screening in size. The occurrence of the Guadalupian trio (large fusulines, corals, large bivalves) is paleogeographically limited to Tethys and low-latitude Panthalassa, suggesting their good adaptation to tropical to subtropical, warm, and shallow-water environments. In particular, the unusually large-shelled (over 50 cm in length) bivalve, Alatoconchidae, has been hitherto reported only from 8 areas, all in the Tethyan and low-latitude Panthalassan domains. The unusual gigantism of these bivalves suggests that they probably have enjoyed symbiosis with photosynthetic algae (Seilacher, 1993), as well as large-tested fusulines and rugose corals. The recent C-isotope study of the paleo-atoll carbonates in Kyushu clarified the development of a transient cooling event in the Capitanian (Kamura event), in the middle of which the extinction of the giant fusulines and bivalves occurred. This suggests that the end-Guadalupian mass extinction may have been triggered by an acute cooling event in the middle of a long-term warming period after the Gondwanan deglaciation in the late Early Permian, thus, the tropical-adapted fauna were likely most severely hit by cooling. The global context of the Kamura event should be tested in contemporary high-latitude marine and non-marine sequences.