College of Geology and Environment, Xi’ an University of Science and Technology
Shaanxi Provincial Key Laboratory of Geological Support for Coal Green Exploitation
Oil & Gas Technology Research Institute, Changqing Oilfield Company, PetroChina/ National Engineering Laboratory forExploration and Development of Low permeability Oil and Gas field
School of Earth Scicenes and Engineering, Xi’ an Shiyou University

为了明确鄂尔多斯盆地中东部中侏罗统延安组沉积时期的古环境特征,利用泥岩样品进行微量元素和稀土元素等分析测试,对测试结果进行统计分析,结合古植物和孢粉组合等特征,对盆地中东部延安期的古环境进行恢复重建。结果表明:锶、硼、相当硼、镓、锂、镍、Sr/Ba、B/Ga、Rb/K2O和Th/U的数值说明延安期水体主体为淡水-半咸水环境;Fe2+/Fe3+、Ni/Co、V/Cr、V/(V+Ni)、U/Th、δU和Cu/Zn的数值反映延安期主要存在弱还原弱氧化-氧化的沉积条件;通过对比延安组和直罗组Sr/Cu、Mg/Ca、Rb/Sr、FeO/MnO、Al2O3/MgO和Sr/Ba的数值,结合古植物和孢粉组合特征,认为从早侏罗世富县期到中侏罗世延安期,再到中侏罗世直罗期,鄂尔多斯盆地中东部经历了炎热半干旱半湿润—温暖湿润—炎热半干旱半湿润的气候变化过程。研究成果对于恢复中侏罗世延安期盆地沉积格局、重建古地理及成藏研究具有重要意义。

In order to clarify the paleoenvironment characteristics of the Middle Jurassic Yan’ an For-mation sedimentary period in the central and eastern part of Ordos Basin, mudstone samples were usedto test and analyze the trace elements and rare earth elements. The test results were statistically ana-lyzed, and the paleoenvironment of the Yan’ an period in the central and eastern part were restored and第 5 期范 萌 萌 , 等 : 鄂 尔 多 斯 盆 地 中 东 部 延 安 组 古 环 境 恢 复reconstructed combined with the characteristics of ancient plants and pollen assemblages in view. Theresults show that the values of Sr, B, equivalent B, Ga, Li, Ni, Sr/ Ba, B / Ga, Rb / K2O and Th / U indi-cate the main body of water in Yan’ an period is a fresh-brackish water environment. Fe2 + / Fe3 + , Ni/Co, V/ Cr, V/ ( V + Ni) , U/ Th, δU and Cu / Zn indicate that there were mainly weak reduction-weak ox-idation to oxidation sedimentary conditions during the Yan’ an period. By comparing the values of Sr/Cu, Mg / Ca, Rb / Sr, FeO/ MnO, Al2O3 / MgO, and Sr/ Ba between the Yan’ an Formation and the ZhiluoFormation, considering the characteristics of ancient plant and pollen assemblages, it is believed thatfrom the Fuxian period of the Early Jurassic to the Yan’ an period of the Middle Jurassic, and then tothe Zhiluo period of the Middle Jurassic, the central and eastern part ofOrdos Basin experienced a cli-mate change process of hot semi-arid and semi-humid to warm humid to hot semi-arid and semi-humid.The research results are of great significance for restoring the sedimentary pattern, reconstructing paleo-geography, and exploring reservoir formation of the Ordos Basin during the Yan’ an period of the Mid-dle Jurassic.

国家自然科学基金项目(41802187)