11:15 AM - 11:30 AM
[BPT06-03] The Carbon isotope stratigraphy of the upper part of the Iwaizaki limestone in the middle permian.
Keywords:mass extinction, Permian, limestone, G-L boundary
The main extinction of well-adapted tropical fauna, such as large-tested fusuline (Lepidolina), occurred particularly during the deposition of Unit 8. On the other hand, isotope ratios of organic carbon for Unit 8 range in -25.4 to -22.3‰. A preliminary reported isotope ratio of inorganic carbon from the same section was about +4‰ (Zakharov et al., 2000); thus the gap between the two is about 26~29‰. The isotopic fractionation was probably induced by normal photosynthesis in the shallow marine setting under which the Iwaizaki limestone was deposited. The relatively high values of both inorganic and organic carbon isotope ratios likely recorded the “Kamura event” (Isozaki et al., 2007, 2011). So far, the evidence for the “Kamura event” was limited solely to the strata deposited in tropical settings, such as the Iwato and Akasaka limestones in Japan, and the Velebit limestone in Croatia. This study first suggests that the collapse of warm-water reef community in the relatively high latitude domain was related also to a global cooling. The Capitanian Chandalez limestone of the Senkina Shapka section in Primorye, Far East Russia, was deposited probably next to the Iwaizaki limestone, and its carbon isotope signature is also under analysis.