期刊
JOURNAL OF ASIAN EARTH SCIENCES
卷 67-68, 期 -, 页码 51-62出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.jseaes.2013.02.009
关键词
Guadalupian; Lopingian; Carbon isotopic negative excursions; Disphotic oxygen-depletion; Multiple upwelling; Extinction
资金
- Japan Society for the Promotion of Science [16204040, 20224012]
- National Nature Science Foundation of China [1212011120116, 1212011120143]
- University of Tokyo
- Global COE program Earth to Earths
- Tokyo Institute of Technology
- Grants-in-Aid for Scientific Research [20224012] Funding Source: KAKEN
In order to examine the causal relationships between the carbon cycle in a shallow euphotic zone and the environmental changes in a relatively deep disphotic zone at the end-Guadalupian (Middle Permian), isotopic compositions of carbonate carbon (delta C-13(carb)) of the Guadalupian-Lopingian (Upper Permian) rocks were analyzed in the Chaotian section in northern Sichuan, South China. By analyzing exceptionally fresh drill core samples, a continuous chemostratigraphic record was newly obtained. The ca. 65 m-thick analyzed carbonate rocks at Chaotian comprise three stratigraphic units, i.e., the Limestone Unit of the Guadalupian Maokou Formation, the Mudstone Unit of the Maokou Formation, and the lower part of the Wuchiapingian (Lower Lopingian) Wujiaping Formation, in ascending order. The Limestone Unit of the Maokou Formation is characterized by almost constant delta C-13(carb) values of ca. +4 parts per thousand followed by an abrupt drop for 7 parts per thousand to -3 parts per thousand in the topmost part of the unit. In the Mudstone Unit of the Maokou Formation, the delta C-13(carb) values are rather constant around +2 parts per thousand, although distinct three isotopic negative excursions for 3 parts per thousand, from ca. +2 to -1 parts per thousand occurred in the upper part of the unit. In the lower part of the Wujiaping Formation, the delta C-13(carb) values monotonously increase for 5 parts per thousand from ca. 0 to +5 parts per thousand. The present data newly demonstrated four isotopic negative excursions in the topmost part of the Maokou Formation in the Capitanian (Late Guadalupian) at Chaotian. It is noteworthy that these negative excursions are in accordance with the emergence of an oxygen-depleted condition on the relatively deep disphotic slope/basin on the basis of litho- and bio-facies characteristics. They suggest multiple upwelling of oxygen-depleted waters with dissolved inorganic carbon of relatively low carbon isotope values along the continental margin, from the deeper disphotic slope/basin to the shallower euphotic shelf, slightly before the end-Guadalupian extinction. Although the negative excursions at Chaotian are apparently correlated with the previously proposed large negative excursion in the middle Capitanian in South China, the age difference according to the biostratigraphic constraints clearly exclude this interpretation. The isotopic negative excursions at Chaotian are unique and no similar isotopic signal in the same period has been reported elsewhere. The multiple upwelling of oxygen-depleted waters onto the euphotic shelf may have represented local phenomena that occurred solely around northwestern South China. (C) 2013 Elsevier Ltd. All rights reserved.
作者
我是这篇论文的作者
点击您的名字以认领此论文并将其添加到您的个人资料中。
推荐
暂无数据