Geochemical evidence for non-marine depositional environment of foraminiferal fossils from the Nihewan Basin, China |
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Authors: | Shijie Wang Xiuming Liu Yuhe Jia Limin Dong and Hongbing Ji |
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Institution: | State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, China |
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Abstract: | From the first finding in 1970s, the findings of foraminiferal fossil assemblages in inland basins have been reported from
time to time, especially in recent years. The debates on the depositional environment of foraminiferal fossils have become
the hot spot of researches again in China. Based on the researches of trace element geochemistry and electron scanning microscope
of shells of Quaternary foraminiferal fossils from the Xiaodukou section in the inland Nihewan basin, the original 87Sr/86Sr and other geochemical information of shells were believed to be preserved well and could be used to rebuild the geochemistry
of contemporary waters where foraminifera deposited, although there existed some effects of burial diagenesis on the geochemistry
of shells to a certain extent. The 87Sr/86Sr ratios of well-preserved Xiaodukou foraminiferal shells were measured, giving a range of 0.711190±25–0.712018±14, apparently
higher than the value of contemporary seawater (0.709087–0.709147) and similar to that of the Sanggan River, proving that
it represented the value of the ancient lacustrine water. The hyperbolic mixing models of 87Sr/86Sr-palaeosalinity and 87Sr/86Sr-Sr/Ca indicated that the contemporary waters where Xiaodukou foraminifera inhabited was an inland lake and there was no
seawater input to the depositional environment. |
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Keywords: | continental foraminiferal fossil burial diagenesis criteria of 87Sr/86Sr-palaeosalinity hyperbolic mixing model criteria of 87Sr/86Sr-Sr/Ca hyperbolic mixing model Xiaodukou section |
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