Shoreline-neritic Mixed Sedimentation Response to Sea Level Change and Paleoclimate: A case study from Carboniferous in Tarim Basin

Key words: 
• Tarim Basin /
• mixed sedimentation /
• paleo-environment /
• paleoclimate /
• sea level change

Abstract: The characteristics of siliciclastic-carbonate mixed sedimentary environment still remains unknown, resulting in poor understanding of distribution of mixed rock. In this study, the sedimentary environments and environmental parameters of Carboniferous in Bamai area, Tarim Basin are deeply studied, using observation of thin sections, measurement of minerals composition, and elements composition. The mixed rocks were deposited, carbonate restricted platform and open platform. The concentrations of Ti, Rb, K, Al are used to divide the degrees of mixed sedimentation into four levels due to their good relationship with the degree of mixing. The salinity was reflected by Na content and Na/Ca. The depth of water was reflected by Mn/Fe and Sr content. The redox condition was reflected by V/(V+Ni). And, the paleoclimate was analyzed from Ti/Al and Mg/Sr. The result of geochemical indices shows the mixed sedimentation beyond Ⅱ level occurred at humid climate, while there was no obvious mixing at arid climate. Meanwhile, most mixed sedimentation accompanied by sea level fall. On the open platform, there was only I level mixed sedimentation, while Ⅲ-IV level mixed sedimentation developed on the barrier coast and restricted platform. The mixed sedimentation in each depositional environment can record the change of sea level and paleoclimate.