CAPITANIAN (PERMIAN) LOW-LATITUDE SHELF LIMESTONE IN JAPAN AND THE G-LB EVENT IN FAR-EAST SOUTH CHINA

The Capaitanin (Upper Guadlupian) Iwaizaki Limestone in the South Kitakami belt, NE Japan, is a ca. 200 m thick sedimentary package of typical shallow marine shelf carbonates associated in part with patch reef structures. A bizzare bivalve assemblage dominated by Family Alatoconchidae was newly found from the upper part of the limestone. Its unique association with large-tested fusulines (Lepidolina) and rugose corals (Waagenophyllum), just like those from the Tethyan tropical domains, suggests that a photosymbiotic habitat has developed under oligotrophic conditions. The Alatoconchidae-bearing fauna from the Iwaizaki Limestone indicates that the South Kitakami belt was located in the mid-Permian low-latitudes. In the uppermost part of the limestone, the gigantic bivalves and large-tested fusulines disappeared sharply. Our preliminary chemostratigraphic analyses identified the unique signatures of the Capitanian Kamura event. Although the overlying fossil-poor units hinder a precise placement of the G-LB horizon, the uppermost Iwaizaki Limestone likely includes the significant interval that recorded the end-Guadalupian extinction and relevant environmental changes. The latest data of detrital zircon suggest an intimate connection between the S. Kitakami belt and the Pacific margin of South China.