Sr isotope excursion across the Precambrian-Cambrian boundary in the Three Gorges area, South China

Yusuke Sawaki, Takeshi Ohno, Yusuke Fukushi, Tsuyoshi Komiya, Tomoko Ishikawa, Takafumi Hirata, Shigenori Maruyama

Research output: Contribution to journalArticle

50 Citations (Scopus)

Abstract

The Precambrian/Cambrian (PC/C) boundary is one of the most important intervals for the evolution of life. However, the scarcity of well-preserved outcrops across the boundary leaves an obstacle in decoding surface environmental changes and patterns of biological evolution. In south China, strata through the PC/C boundary are almost continuously exposed and contain many fossils, suitable for study of environmental and biological change across the PC/C boundary. We undertook deep drilling at four sites in the Three Gorges area to obtain continuous and fresh samples without surface alteration and oxidation. 87Sr/86Sr ratios of the fresh carbonate rocks, selected based on microscopic observation and geochemical signatures of Mn/Sr and Rb/Sr ratios, aluminum and silica contents, and δ13C and δ18O values, were measured with multiple collector-inductively coupled plasma-mass spectrometric techniques. The chemostratigraphy of 87Sr/86Sr ratios of the drilled samples displays a smooth curve and a large positive anomaly just below the PC/C boundary between the upper part of Baimatuo Member of the Dengying Formation and the lower part of the Yanjiahe Formation. The combination of chemostratigraphies of δ13C and 87Sr/86Sr indicates that the 87Sr/86Sr excursions preceded the δ13C negative excursion, and suggests that global regression or formation of the Gondwana supercontinent, possibly together with a high atmospheric pCO2, caused biological depression.

Original languageEnglish
Pages (from-to)134-147
Number of pages14
JournalGondwana Research
Volume14
Issue number1-2
DOIs
Publication statusPublished - Aug 2008
Externally publishedYes

Fingerprint

Precambrian-Cambrian boundary
gorge
isotope
chemostratigraphy
deep drilling
supercontinent
carbonate rock
Gondwana
environmental change
outcrop
aluminum
silica
fossil
anomaly
plasma
oxidation

Keywords

  • δC, chemostratigraphy
  • Gondwana
  • Precambrian-Cambrian boundary
  • Sr isotope

ASJC Scopus subject areas

  • Earth and Planetary Sciences (miscellaneous)

Cite this

Sawaki, Y., Ohno, T., Fukushi, Y., Komiya, T., Ishikawa, T., Hirata, T., & Maruyama, S. (2008). Sr isotope excursion across the Precambrian-Cambrian boundary in the Three Gorges area, South China. Gondwana Research, 14(1-2), 134-147. https://doi.org/10.1016/j.gr.2007.11.002

Sr isotope excursion across the Precambrian-Cambrian boundary in the Three Gorges area, South China. / Sawaki, Yusuke; Ohno, Takeshi; Fukushi, Yusuke; Komiya, Tsuyoshi; Ishikawa, Tomoko; Hirata, Takafumi; Maruyama, Shigenori.

In: Gondwana Research, Vol. 14, No. 1-2, 08.2008, p. 134-147.

Research output: Contribution to journalArticle

Sawaki, Y, Ohno, T, Fukushi, Y, Komiya, T, Ishikawa, T, Hirata, T & Maruyama, S 2008, 'Sr isotope excursion across the Precambrian-Cambrian boundary in the Three Gorges area, South China', Gondwana Research, vol. 14, no. 1-2, pp. 134-147. https://doi.org/10.1016/j.gr.2007.11.002
Sawaki, Yusuke ; Ohno, Takeshi ; Fukushi, Yusuke ; Komiya, Tsuyoshi ; Ishikawa, Tomoko ; Hirata, Takafumi ; Maruyama, Shigenori. / Sr isotope excursion across the Precambrian-Cambrian boundary in the Three Gorges area, South China. In: Gondwana Research. 2008 ; Vol. 14, No. 1-2. pp. 134-147.
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