中国科学院南京地质古生物研究所机构知识库

Conodont,C isotope and fossil and facies data are presented for the Capitanian (Middle Permian) mass extinction record seen in platform carbonates (Maokou and Wuchiaping formations) of South China, where limestones interdigitate with the volcanic succession of the Emeishan large igneous province The Maokou Formation provides an extinction record marked by the loss of keriothecal-walled fusulinaceans and a turnover in calcareous algae In sections within the Emeishan province this crisis occurs at the base of the oldest record of volcanism from the Jinogondolella altudaensis conodont zone (of mid-Capitanian age) Around the periphery of the Emeishan province this extinction level lies within the upper part of the Maokou Formation at a level where platform carbonate deposition was frequently interrupted by thick volcanic ash depositional events The assemblages of the uppermost Maokou Formation are characterised by typical "Late Permian" taxa although these levels still he within the Middle Permian (Guadalupian Series) "Disaster" taxa, such as Earlandia and Diplosphaerina are locally prolifically abundant in the aftermath of the mass extinction The crisis is particularly noteworthy amongst photosynthetic taxa such as calcareous algae and fusulinaceans that probably harboured photosymbionts. Therefore, a kill mechanism involving cooling from explosive volcanism and potentially acid rain from sulphate aerosols appears appropriate. A composite delta C-13(carb) curve, calibrated against a high-resolution conodont biostratigraphy reveals a major intra-Capitanian negative excursion (of >5 parts per thousand) superimposed on typically heavy (4-5 parts per thousand.) Middle Permian values This curve can also be recognised in Panthalassan seamount carbonates of Japan although this requires reassignment of apparently Upper Permian limestones to the Middle Permian. In both China and Japan the Capitanian mass extinction occurs during the early stage of this major. intra-Capitanian negative excursion Assuming typical platform carbonate accumulation rates, the records of the Maokou Formation suggest delta C-13(carb) values fell at similar to 001 parts per thousand/kyr suggesting a catastrophic origin (such as gas hydrate destabilisation) is unlikely, although a volcanic source is possible (C) 2010 Elsevier BV All rights reserved