2006 Philadelphia Annual Meeting (2225 October 2006)
Paper No. 137-6
Presentation Time: 9:15 AM-9:30 AM


ISOZAKI, Yukio, Univ Tokyo, 3-8-1 Komaba, Meguro-ku, Tokyo 153-8902 Japan, isozaki@ea.c.u-tokyo.ac.jp

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.

2006 Philadelphia Annual Meeting (2225 October 2006)
General Information for this Meeting
Session No. 137
Mass Extinctions: New Approaches Analyzing Process Links Between Land and Sea
Pennsylvania Convention Center: 105 AB
8:00 AM-12:00 PM, Tuesday, 24 October 2006

Geological Society of America Abstracts with Programs, Vol. 38, No. 7, p. 338

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