The Steptoean Positive Carbon Isotope Excursion (SPICE) event at ca. 497−494 Ma was a major carbon-cycle perturbation of the late Cambrian that coincided with rapid diversity changes among trilobites. Several scenarios (e.g., climatic/oceanic cooling and seawater anoxia) have been proposed to account for an extinction of trilobites at the onset of SPICE, but the exact mechanism remains unclear. Here, we present a chemostratigraphic study of carbonate carbon and carbonate-associated sulfate sulfur isotopes (δ13Ccarb and δ34SCAS) and elemental redox proxies (UEF, MoEF, and Corg/P), augmented by secular trilobite diversity data, from both upper slope (Wangcun) and lower slope (Duibian) successions from the Jiangnan Slope, South China, spanning the Drumian to lower Jiangshanian. Redox data indicate locally/regionally well-oxygenated conditions throughout the SPICE event in both study sections except for low-oxygen (hypoxic) conditions within the rising limb of the SPICE (early-middle Paibian) at Duibian. As in coeval sections globally, the reported δ13Ccarb and δ34SCAS profiles exhibit first-order coupling throughout the SPICE event, reflecting co-burial of organic matter and pyrite controlled by globally integrated marine productivity, organic preservation rates, and shelf hypoxia. Increasing δ34SCAS in the “Early SPICE” interval (late Guzhangian) suggests that significant environmental change (e.g., global-oceanic hypoxia) was under way before the global carbon cycle was markedly affected. Assessment of trilobite range data within a high-resolution biostratigraphic framework for the middle-late Cambrian facilitated re-evaluation of the relationship of the SPICE to contemporaneous biodiversity changes. Trilobite diversity in South China declined during the Early SPICE (corresponding to the End-Marjuman Biomere Extinction, or EMBE, of Laurentia) and at the termination of the SPICE (corresponding to the End-Steptoean Biomere Extinction, or ESBE, of Laurentia), consistent with biotic patterns from other cratons. We infer that oxygen minimum zone and/or shelf hypoxia expanded as a result of locally enhanced productivity due to intensified upwelling following climatic cooling, and that expanded hypoxia played a major role in the EMBE at the onset of SPICE. During the SPICE event, global-ocean ventilation promoted marine biotic recovery, but termination of SPICE-related cooling in the late Paibian may have reduced global-ocean circulation, triggering further redox changes that precipitated the ESBE. Major changes in both marine environmental conditions and trilobite diversity during the late Guzhangian demonstrate that the SPICE event began earlier than the Guzhangian-Paibian boundary, as previously proposed.
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Research Article|
May 12, 2023
Environmental and trilobite diversity changes during the middle-late Cambrian SPICE event
Lei Zhang;
Lei Zhang
1
State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan 430074, China
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Thomas J. Algeo;
Thomas J. Algeo
1
State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan 430074, China2
State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan 430074, China3
Department of Geosciences, University of Cincinnati, Cincinnati, Ohio 45221-0013, USA
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Laishi Zhao;
Laishi Zhao
1
State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan 430074, China
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Tais W. Dahl;
Tais W. Dahl
1
State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan 430074, China4
Globe Institute, University of Copenhagen, DK-1350 Copenhagen, Denmark
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Zhong-Qiang Chen;
Zhong-Qiang Chen
1
State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan 430074, China2
State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan 430074, China
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Zihu Zhang;
Zihu Zhang
5
State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation & Institute of Sedimentary Geology, Chengdu University of Technology, Chengdu 610059, China6
Key Laboratory of Deep-time Geography and Environment Reconstruction and Applications of Ministry of Natural Resources, Chengdu University of Technology, Chengdu 610059, China7
International Center for Sedimentary Geochemistry and Biogeochemistry Research, Chengdu University of Technology, Chengdu 610059, China
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Simon W. Poulton;
Simon W. Poulton
1
State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan 430074, China8
School of Earth and Environment, University of Leeds, Leeds LS2 9JT, UK
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Nigel C. Hughes;
Nigel C. Hughes
9
Department of Earth and Planetary Sciences, University of California, Riverside, California 92521, USA
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Xueqing Gou;
Xueqing Gou
1
State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan 430074, China
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Chao Li
Chao Li
5
State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation & Institute of Sedimentary Geology, Chengdu University of Technology, Chengdu 610059, China6
Key Laboratory of Deep-time Geography and Environment Reconstruction and Applications of Ministry of Natural Resources, Chengdu University of Technology, Chengdu 610059, China7
International Center for Sedimentary Geochemistry and Biogeochemistry Research, Chengdu University of Technology, Chengdu 610059, China
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Lei Zhang
1
State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan 430074, China
Thomas J. Algeo
1
State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan 430074, China2
State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan 430074, China3
Department of Geosciences, University of Cincinnati, Cincinnati, Ohio 45221-0013, USA
Laishi Zhao
1
State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan 430074, China
Tais W. Dahl
1
State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan 430074, China4
Globe Institute, University of Copenhagen, DK-1350 Copenhagen, Denmark
Zhong-Qiang Chen
1
State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan 430074, China2
State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan 430074, China
Zihu Zhang
5
State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation & Institute of Sedimentary Geology, Chengdu University of Technology, Chengdu 610059, China6
Key Laboratory of Deep-time Geography and Environment Reconstruction and Applications of Ministry of Natural Resources, Chengdu University of Technology, Chengdu 610059, China7
International Center for Sedimentary Geochemistry and Biogeochemistry Research, Chengdu University of Technology, Chengdu 610059, China
Simon W. Poulton
1
State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan 430074, China8
School of Earth and Environment, University of Leeds, Leeds LS2 9JT, UK
Nigel C. Hughes
9
Department of Earth and Planetary Sciences, University of California, Riverside, California 92521, USA
Xueqing Gou
1
State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan 430074, China
Chao Li
5
State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation & Institute of Sedimentary Geology, Chengdu University of Technology, Chengdu 610059, China6
Key Laboratory of Deep-time Geography and Environment Reconstruction and Applications of Ministry of Natural Resources, Chengdu University of Technology, Chengdu 610059, China7
International Center for Sedimentary Geochemistry and Biogeochemistry Research, Chengdu University of Technology, Chengdu 610059, China
Publisher: Geological Society of America
Received:
07 Jun 2022
Revision Received:
05 Jan 2023
Accepted:
23 Feb 2023
First Online:
12 May 2023
Online ISSN: 1943-2674
Print ISSN: 0016-7606
© 2023 Geological Society of America
GSA Bulletin (2023)
Article history
Received:
07 Jun 2022
Revision Received:
05 Jan 2023
Accepted:
23 Feb 2023
First Online:
12 May 2023
Citation
Lei Zhang, Thomas J. Algeo, Laishi Zhao, Tais W. Dahl, Zhong-Qiang Chen, Zihu Zhang, Simon W. Poulton, Nigel C. Hughes, Xueqing Gou, Chao Li; Environmental and trilobite diversity changes during the middle-late Cambrian SPICE event. GSA Bulletin 2023; doi: https://doi.org/10.1130/B36421.1
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Index Terms/Descriptors
- Arthropoda
- biodiversity
- biostratigraphy
- C-13/C-12
- Cambrian
- carbon
- carbon cycle
- carbonates
- chemostratigraphy
- Eh
- geochemical cycle
- isotope ratios
- isotopes
- Middle Cambrian
- North Pacific
- Northwest Pacific
- ocean circulation
- Pacific Ocean
- paleo-oceanography
- paleocirculation
- Paleozoic
- S-34/S-32
- South China Sea
- stable isotopes
- succession
- sulfur
- Trilobita
- Trilobitomorpha
- Upper Cambrian
- West Pacific
Latitude & Longitude
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