Abstract
The mudstone and marl from western Hoh Xil basin, located in Tibet of the west of China, were deposited in Tertiary lacustrine environment. Investigation of organic geochemistry, sedimentary characteristics, and 13C in kerogen was conducted to analyze the sedimentary environment, biomarkers, paleoclimate, and source of organic matter during deposition. The Cenozoic sedimentary facies of the basin included upper lacustrine facies and lower alluvial fan facies, which belong to Miocene Wudaoliang Formation and Oligocene Yaxicuo Group, respectively. The Miocene marl-sandstone-mudstone from Wudaoliang Formation was analyzed. Maceral composition was dominated by amorphous organic matter. T max values indicated that the mudstones were thermally immature-low maturity with mainly type II and III organic matter, while organic matter in marlite belongs mainly to type I-II1 with low maturity-maturity stage. The biomarkers showed the characteristics of odd-over-even predominance of long-chain n-alkanes, higher proportion of C27 sterane in most of the samples, heavy δ13Corg composition, low Pr/Ph ratios (0.11-0.36), and so on. Organic geochemistry indicated that the organic matter originated from bacteria, algae, and higher plants. The rocks were formed in reducing environments with stratified water column and high productivity. The paleoclimate became more humid during depositional stage in the western Hoh Xil basin.
Highlights
After years of geological investigation, the Hoh Xil basin was considered to be one of the important targets of hydrocarbon resource exploration for continental basin of Tibetan Plateau
We found two continental facies oil and gas Cenozoic basin belts of Bangong-Nujiang and Jinsha River on Tibetan Plateau
Understanding the geological survey of the western Hoh Xil basin (WHXB) is very important to recognize the overall situation of Cenozoic basins on Tibetan Plateau and the plateau lifting
Summary
After years of geological investigation, the Hoh Xil basin was considered to be one of the important targets of hydrocarbon resource exploration for continental basin of Tibetan Plateau. We found two continental facies oil and gas Cenozoic basin belts of Bangong-Nujiang and Jinsha River on Tibetan Plateau. These basins had good prospects for preserving oil and gas resources and exploration potential. The Hoh Xil basin has been confirmed existing a better prospect for preserving oil and gas too [3,4,5]. Understanding the geological survey of the western Hoh Xil basin (WHXB) is very important to recognize the overall situation of Cenozoic basins on Tibetan Plateau and the plateau lifting. The pivotal aim is to analyze paleoenvironment and paleoclimatic changes, to give the other geologists more information of Tibet
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