期刊
PALAEOGEOGRAPHY PALAEOCLIMATOLOGY PALAEOECOLOGY
卷 522, 期 -, 页码 40-51出版社
ELSEVIER SCIENCE BV
DOI: 10.1016/j.palaeo.2019.03.012
关键词
U-Pb age; Late Permian volcanism; Chemical weathering; Sedimentary transition; Tibet
资金
- National Natural Science Foundation of China [41172098, 40972087]
- Oil and Gas Survey in the Jinxinghu-Longeni area of the Qiangtang Basin [DD20160159]
The Permian-Triassic boundary (PTB) events such as carbon-isotope excursion, volcanism, and environmental disturbances are not well understood in an ocean island setting. Here, we develop a new case study for the Permian-Triassic transition in the Qiangtang Basin, Tibet, by combining existing biostratigraphy, new carbon isotope data, sedimentological data, U-Pb zircon age, mineralogical and geochemical data. These new data defined the Permian-Triassic transition age as about 252.3 +/- 0.9 Ma, corresponding to the lowermost sea level. A long-term negative carbonate carbon isotope trend is present at the same stratigraphic level in different depositional environments, strongly suggesting its global nature. However, our new ocean island setting is characterized by an abrupt shift in carbon isotope values across the level, which is different from many chemostrtigraphic studies that show a gradual shift in carbon isotope values across the event horizon. The most likely explanation for the abrupt shift in C-13 values is a sedimentary hiatus at this level in the study section. Three-stage climatic models through the PTB in the ocean island setting are identified: Stage 1 is characterized by a warm and humid climate with moderate chemical weathering; while a hot and humid climate with intense chemical weathering dominates stage 2; the climate in stage 3 is a relatively hot and arid climatic condition with weak chemical weathering.
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