TY - JOUR
T1 - A high-resolution chemostratigraphy of post-Marinoan Cap Carbonate using drill core samples in the Three Gorges area, South China
AU - Sato, Hisatoshi
AU - Tahata, Miyuki
AU - Sawaki, Yusuke
AU - Maruyama, Shigenori
AU - Yoshida, Naohiro
AU - Shu, Degan
AU - Han, Jian
AU - Li, Yong
AU - Komiya, Tsuyoshi
N1 - Funding Information:
This work was partly supported by grants “ Multi-step evolution of multicellular animals (No. 23340152 )”, and “ Toward establishment of chemical paleontology (No. 23654176 )”, as well as the Global COE Program “From the Earth to ‘Earths’” from the Ministry of Education, Culture, Sports, Science and Technology, Japan , and supported by a grant from the Mitsubishi Foundation (T.K.). Each is gratefully acknowledged.
Publisher Copyright:
© 2015 China University of Geosciences (Beijing) and Peking University. Production and hosting by Elsevier B.V.
PY - 2016/7/1
Y1 - 2016/7/1
N2 - Cap Carbonates overlie the Marinoan Snowball Earth-related glacial diamictite, and possibly record the drastic surface environmental change and biological evolution after the Snowball Earth. We conducted on-land drilling from the Liantuo Formation, through the Nantuo, to the lower Doushantuo Formation in the Three Gorges area of South China to collect fresh, continuous samples in the Three Gorges area. We obtained high-resolution chemostratigraphies of δ13C and δ18O values of carbonates from the topmost part of the Nantuo Formation to the Cap Carbonate, in order to decode the detailed surface environmental change in the shallow marine setting. The δ13C chemostratigraphy possesses some unique characteristics: (1) stable δ13C values as a whole, but ubiquitous low δ13C anomalies through the Cap Carbonate, (2) increase of the δ13C values from -3 to +5‰ across the C2/C3 boundary, (3) no δ13C anomaly between the C1 and C2 boundary, and (4) presence of an anomalous high δ13C value (+2.3‰) and a faint positive correlation between δ13C and δ18O values in the C1 unit. Evidence of quite low δ13C anomalies (with a nadir of -41‰), ubiquitous negative δ13C anomalies through the Cap Carbonate, and a high δ13C anomaly accompanied with a faint positive correlation between δ13C and δ18O values in the C1 unit supports decomposition and formation of methane hydrate during Cap Carbonate formation. The drastic increase of δ13C values from the upper C2 to C3 units indicates enhancement of primary productivity and organic carbon burial, possibly due to high continental fluxes after the Snowball Earth event, evidenced by high Sr isotope values. The increase is restricted to the proximal side of the inner shelf in South China, and the timing of the increase of δ13C values of carbonates is earlier at Three Gorges area than any other area, suggesting that the enhancement of primary productivity started in the proximal environment because of higher continental influxes. The increase in oxygen contents of seawater due to the enhanced primary productivity possibly resulted in the emergence of multicellular animals soon after Cap Carbonate deposition.
AB - Cap Carbonates overlie the Marinoan Snowball Earth-related glacial diamictite, and possibly record the drastic surface environmental change and biological evolution after the Snowball Earth. We conducted on-land drilling from the Liantuo Formation, through the Nantuo, to the lower Doushantuo Formation in the Three Gorges area of South China to collect fresh, continuous samples in the Three Gorges area. We obtained high-resolution chemostratigraphies of δ13C and δ18O values of carbonates from the topmost part of the Nantuo Formation to the Cap Carbonate, in order to decode the detailed surface environmental change in the shallow marine setting. The δ13C chemostratigraphy possesses some unique characteristics: (1) stable δ13C values as a whole, but ubiquitous low δ13C anomalies through the Cap Carbonate, (2) increase of the δ13C values from -3 to +5‰ across the C2/C3 boundary, (3) no δ13C anomaly between the C1 and C2 boundary, and (4) presence of an anomalous high δ13C value (+2.3‰) and a faint positive correlation between δ13C and δ18O values in the C1 unit. Evidence of quite low δ13C anomalies (with a nadir of -41‰), ubiquitous negative δ13C anomalies through the Cap Carbonate, and a high δ13C anomaly accompanied with a faint positive correlation between δ13C and δ18O values in the C1 unit supports decomposition and formation of methane hydrate during Cap Carbonate formation. The drastic increase of δ13C values from the upper C2 to C3 units indicates enhancement of primary productivity and organic carbon burial, possibly due to high continental fluxes after the Snowball Earth event, evidenced by high Sr isotope values. The increase is restricted to the proximal side of the inner shelf in South China, and the timing of the increase of δ13C values of carbonates is earlier at Three Gorges area than any other area, suggesting that the enhancement of primary productivity started in the proximal environment because of higher continental influxes. The increase in oxygen contents of seawater due to the enhanced primary productivity possibly resulted in the emergence of multicellular animals soon after Cap Carbonate deposition.
KW - Cap Carbonate
KW - Carbon isotope chemostratigraphy
KW - Ediacaran
KW - Marinoan Snowball Earth
KW - Methane hydrate
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U2 - 10.1016/j.gsf.2015.07.008
DO - 10.1016/j.gsf.2015.07.008
M3 - Article
AN - SCOPUS:84951037380
VL - 7
SP - 663
EP - 671
JO - Geoscience Frontiers
JF - Geoscience Frontiers
SN - 1674-9871
IS - 4
ER -