Oxygen and carbon isotopic records of the Late Triassic Carnian pluvial event deposits in northwestern Sichuan Province
Distinct lithological mutations from grey ooides, sponge reef limestone to grayish black shale, and then argillaceous siltstone are distinguished from the Upper Triassic Carman marine sediments in the Mianzhu and Anxian counties in northwestern Sichuan Province, which is very similar to the sediments representing the Carnian pluvial event in western Tethys area. The stable oxygen and carbon isotop-ic compositions of the Carnian fossils of foraminifer, bivalve and brachiopodous shells and plant leaves are analyzed using laser micro-sampling technique. The analysis results indicate the slightly lower δ18O values and remarkable lower δ13C values of the Upper Carnian than those of the Lower Carnian. It's believed that the isotopic compositions reflect that fresh water input into the Paleotethys ocean. We suggest that the Carnian pluvial event severely affected the deposits in the eastern Tethys area. The freshwater input in the hu-mid conditions is one of the causes that triggered the periodic deaths and finally disappearing of the sponge reefs in the study area.
Carnian pluvial eventisotopesponge reefTriassicTethysmegamonsoonnorthwestern Sichuan Province
国家科技期刊平台
NSTL
万方数据
维普
