Early Paleogene climatic features in Emei area,western Sichuan: evidence from geochemistry and magnetic susceptibility in the lower part of the Mingshan Formation
Tai Zi-Han1, Xiang Fang2,3, Chen Zhuo-Hua4, Li Lei1, Yu Xian-Tao3
1 College of Earth Sciences,Chengdu University of Technology,Chengdu 610059,China; 2 State Key Laboratory of Oil & Gas Reservoir Geology and Exploitation,Chengdu University of Technology,Chengdu 610059,China; 3 Institute of Sedimentary Technology,Chengdu University of Technology,Chengdu 610059,China; 4 Sichuan Science and Technology Museum,Chengdu 610011,China
Abstract：The Early Paleogene is a typical “greenhouse climate” period of the Phanerozoic,and also the last warm period prior to the Cenozoic “icehouse climate”. There is a complete set of lacustrine strata of the Paleogene Mingshan Formation in the Emei area,western Sichuan,which can provide useful information about the Cenozoic major geological events and evolution of palaeoclimate. On the basis of previous studies,element ratio,magnetic susceptibility and macroscopic and microscopic characteristics of rocks are used to study the Early Paleogene climate evolution and the formation mechanism of magnetic susceptibility in the Emei area. The results show that the study area had a tropical-subtropical hot and arid climate during the early Paleogene,which was a continuation of the late Cretaceous hot and arid climate,but the dry and heat degree significantly reduced compared with that in the Late Cretaceous. Moreover,there were some cycles of hot and arid-warm and humid climate,and severe climatic fluctuation stage during the Early Paleogene. The dry and wet change of the climate is the main reason for the variability in the magnetic susceptibility of the strata in the study area. Its high values reflect the humid climate,and low values reflect increase of drought. The position where the magnetic susceptibility fluctuates obviously in the strata may correspond to the period when the East Asian monsoon began to affect the Emei area.
Tai Zi-Han,Xiang Fang,Chen Zhuo-Hua et al. Early Paleogene climatic features in Emei area,western Sichuan: evidence from geochemistry and magnetic susceptibility in the lower part of the Mingshan Formation[J]. JOPC, 2021, 23(3): 555-564.
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