Geobiological interpretation of the oxygen-deficient deposits of the Middle Permian marine source rocks in South China:A working hypothesis |
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Authors: | Yan Jiaxin and Liu Xinyu |
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Institution: | (1) Key Laboratory of Biogeology and Environmental Geology of Ministry of Education, China University of Geosciences, Wuhan, 430074, China |
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Abstract: | To decipher the origin of oxygen-deficient shelfal deposits is significant for tracing the distribution of marine source rocks
and interpreting the evolution of depositional environment. The origin of the Middle Permian Chihsia Formation in South China
remains a puzzle for long with its evident oxygen-deficient features but diverse benthos. This paper shows a typical Chihsian
depositional rhythm composed of the massive and the laminated limestones with ecological and geochemical features. Massive
bioclastic limestone from the rhythm was aerobic in paleoxygenation condition indicated by both the ecological and geochemical
features. However, a contradictory oxygenation was inferred for the “laminated” counterpart from the rhythm, with the ecological
signal being aerobic and the geochemical one being anoxic. The difference in ecological and geochemical indications was interpreted
as the instability of paleoxygenation condition in shelf environments, caused by an enhanced paleoproductivity. Rhythmic occurrence
of the oxygen-deficient condition might have been stemmed from paleo-Tethyan paleocurrents flowing across South China.
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Translated from Earth Science—Journal of China University of Geosciences, 2007, 32(6): 789–796 译自: 地球科学—中国地质大学学报] |
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Keywords: | South China Middle Permian oxygen-deficient paleoxygenation condition model |
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