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Geochronological constraint on the Cambrian Chengjiang biota, south China

Yang Chuan, Li Xianhua, Zhu Maoyan, Daniel J. Condon and Chen Junyuan
Geochronological constraint on the Cambrian Chengjiang biota, south China
Journal of the Geological Society of London (March 2018) 175 (4): 659-666

Abstract

The Cambrian Chengjiang biota of South China provides compelling fossil evidence for the rapid appearance of metazoan phyla in Earth history (the 'Cambrian explosion'). However, the timing of the Chengjiang biota is poorly constrained owing to lack of datable rock materials within the Maotianshan Shale that yields the fossils. Here we integrate secondary ion mass spectrometry (SIMS) and chemical ablation isotope dilution thermal ionization mass spectrometry (CA-ID-TIMS) U-Pb analyses of detrital zircons from the Maotianshan Shale to provide high-precision geochronological constraint on the Chengjiang biota. The youngest group of SIMS U-Pb detrital zircon dates yields an age peak at 520 Ma. Six zircons from this group are further dated by the CA-ID-TIMS U-Pb technique, but suggesting that they were not formed from a single zircon growth event. Thereby neither the age peak nor the weighted mean age defined by the youngest SIMS U-Pb dates could represent the maximum depositional age of the Maotianshan Shale. Instead, the youngest CA-ID-TIMS U-Pb date, 518.03 + or - 0.69/0.71 Ma (2sigma , analytical uncertainty/incorporates U-Pb tracer calibration uncertainty), provides the first robust maximum age of the Chengjiang biota. This new geochronological constraint on the Chengjiang biota indicates that the Cambrian explosion reached its major phase around 518.03 + or - 0.69/0.71 Ma, demonstrating a protracted process (>22 myr) for the Cambrian explosion. Supplementary material: SIMS and CA-ID-TIMS zircon U-Pb data are available at https://doi.org/10.6084/m9.figshare.c.4024849


ISSN: 0016-7649
Coden: JGSLAS
Serial Title: Journal of the Geological Society of London
Serial Volume: 175
Serial Issue: 4
Title: Geochronological constraint on the Cambrian Chengjiang biota, south China
Affiliation: Chinese Academy of Sciences, Institute of Geology and Geophysics, Beijing, China
Pages: 659-666
Published: 20180315
Text Language: English
Publisher: Geological Society of London, London, United Kingdom
References: 54
Accession Number: 2018-037138
Categories: GeochronologyGeneral paleontology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. strat. col., sketch map
N24°40'53" - N24°40'53", E102°58'50" - E102°58'50"
Secondary Affiliation: University of Chinese Academy of Sciences, CHN, ChinaBritish Geological Survey, GBR, United Kingdom
Country of Publication: United Kingdom
Secondary Affiliation: GeoRef, Copyright 2022, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data from The Geological Society, London, London, United Kingdom
Update Code: 201820
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