Osmium-isotope evidence for volcanism across the Wuchiapingian-Changhsingian boundary interval

Two negative carbon isotope excursions (3.5-6.5 parts per thousand) across the Wuchiapingian-Changhsingian boundary (WCB) are observed globally (sections in China, Canada, and Iran); however, the causative mechanism of these excursions is debated. Here, high-resolution osmium isotope (Os-187/Os-188...

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Bibliographic Details
Published in:Chemical Geology
Main Authors: Liu, Zeyang, Selby, David, Zhang, Hua, Zheng, Quanfeng, Shen, Shuzhong, Sageman, Bradley B., Grasby, Stephen E., Beauchamp, Benoit
Format: Report
Language:English
Published: ELSEVIER 2019
Subjects:
Wuchiapingian-Changhsingian boundary
Osmium isotope
Volcanism
South China
Canadian arctic
Carbon isotopes
PERMIAN MASS EXTINCTION
STRATOTYPE SECTION
SVERDRUP BASIN
POINT GSSP
CARBON
TIMESCALE
CHEMOSTRATIGRAPHY
STRATIGRAPHY
EXCURSIONS
SHANGSI
Geochemistry & Geophysics
Arctic
Canada
sverdrup basin
Online Access:http://ir.nigpas.ac.cn/handle/332004/29037
https://doi.org/10.1016/j.chemgeo.2019.119313
Description
Summary:Two negative carbon isotope excursions (3.5-6.5 parts per thousand) across the Wuchiapingian-Changhsingian boundary (WCB) are observed globally (sections in China, Canada, and Iran); however, the causative mechanism of these excursions is debated. Here, high-resolution osmium isotope (Os-187/Os-188 or Os-i) chemostratigraphy of four globally correlated WCB sections (3 in China-Meishan, Shangsi and Lianyuan and 1 in Canada - Buchanan Lake) show two separate Osi excursions to less radiogenic compositions that are coincident with the carbon isotope shifts for two of the South China sections (Lianyuan, Meishan). In contrast, only a single Os-i excursion to less radiogenic compositions, coinciding with the earliest Changhsingian carbon isotope shift, is observed for the Shangsi and Buchanan Lake sections. The Os-i shift is interpreted to reflect increased unradiogenic Os input from basaltic magmatism in South China, possibly related to the Emeishan large igneous province (LIP). However, Os-187/Os-188 data suggest that only the earliest Changhsingian volcanism had global impact on both the ocean and atmosphere. The lack of any evidence for a biotic event associated with the WCB therefore may have been due to the more regional rather than global impact of volcanism during the latest Wuchiapingian. In contrast, during the earliest Changhsingian, volcanism was sufficient to cause a more global signal in the ocean osmium record, but was inadequate, or too prolonged, to drive any significant environmental change. Volcanism, however, may have provided the isotopically light carbon that drove the negative carbon isotope excursions across the WCB.

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