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 language | English |
|---|---|
| Pages (from-to) | 134-147 |
| Number of pages | 14 |
| Journal | Gondwana Research |
| Volume | 14 |
| Issue number | 1-2 |
| DOIs | |
| Publication status | Published - Aug 2008 |
| Externally published | Yes |
Fingerprint
Keywords
- δC, chemostratigraphy
- Gondwana
- Precambrian-Cambrian boundary
- Sr isotope
ASJC Scopus subject areas
- Earth and Planetary Sciences (miscellaneous)
Cite this
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 journal › Article
}
TY - JOUR
T1 - Sr isotope excursion across the Precambrian-Cambrian boundary in the Three Gorges area, South China
AU - Sawaki, Yusuke
AU - Ohno, Takeshi
AU - Fukushi, Yusuke
AU - Komiya, Tsuyoshi
AU - Ishikawa, Tomoko
AU - Hirata, Takafumi
AU - Maruyama, Shigenori
PY - 2008/8
Y1 - 2008/8
N2 - 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.
AB - 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.
KW - δC, chemostratigraphy
KW - Gondwana
KW - Precambrian-Cambrian boundary
KW - Sr isotope
UR - http://www.scopus.com/inward/record.url?scp=46149104363&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=46149104363&partnerID=8YFLogxK
U2 - 10.1016/j.gr.2007.11.002
DO - 10.1016/j.gr.2007.11.002
M3 - Article
AN - SCOPUS:46149104363
VL - 14
SP - 134
EP - 147
JO - Gondwana Research
JF - Gondwana Research
SN - 1342-937X
IS - 1-2
ER -