240 / 2019-06-29 18:39:36

Paleosedimentary environment analysis of upper Permian Linxi Formation in Zhalute area, Inner Mongolia

Paleosedimentary environment; the upper Permian Linxi Formation; Zhalute area

Zhalute area of Inner Mongolia is located in the eastern ridge uplift zone of the Daxinganling Mountains, the western subsidence zone of the Songliao Basin, and the northern of the Xar Moron river deep fault, the area mainly expose upper Permian Linxi Formation and late Jurassic volcanic rocks. In this paper, trace elements of dark fine clastic rocks of upper Permian Linxi Formation in Zhalute area are systematically analyzed to discuss the paleoclimate, paleosalinity and paleoredox condition. The samples are taken from Taohaiyingzi outcrop section and LD2 well in Zhalute area.
The ratio of Sr/Cu of the mudstone of Linxi Formation in the Taohayingzi outcrop section in Zalut area is 2.00~3.28 (n=12), and average value is 2.41; the ratio of Sr/Cu of the mudstone of Linxi Formation in LD2 well is 3.83~27.27 (n=12) with an average value of 10.9, and seven samples values are < 10. The results indicate that the sedimentary period of Linxi Formation in Zhalute area should be warm and humid climate.
The B/Ga ratio of samples from Linxi Formation in Taohayingzi outcrop section is 1.74~3.62, with an average value of 2.68, indicating freshwater environment; the B/Ga ratio of the samples from Linxi Formation of LD2 well is 3.31~11.74, with an average value of 6.14, indicating brackish water to saltwater environment with a tendency of dilution from bottom to top. It overall reflects the water environment of Linxi Formation is freshwater environment to brackish water and saltwater environment.
The ratio of V/(V+Ni) of mudstone samples of Linxi Formation in the Taohayingzi outcrop section in Zhalute area is 0.75~0.88 (n=12), with an average value of 0.79; The V/(V+Ni) ratio of mudstone samples of Linxi Formation of LD2 well is 0.67~0.81 (n=12), with an average value of 0.74. It overall reflects the water environment of Linxi Formation is anoxic and reductive environment.
To sum up, the analysis show that the sedimentary period of the upper Permian Linxi Formation in Zhalute area of Inner Mongolia is warm and humid climate condition, the water environment is freshwater to brackish and saltwater, with anoxic and reductive environment.

Keywords: Paleosedimentary environment; the upper Permian Linxi Formation; Zhalute area

Acknowledgments: This work is supported by the Program of China Geological Survey Bureau (Grant No. DD20190097)