鄂尔多斯盆地东缘S区海陆过渡相页岩古环境研究

Study on Paleoenvironment of Marine Continental Transitional Facies Shale in s Area of Eastern Margin of Ordos Basin

鄂尔多斯盆地东缘上古生界海陆过渡相页岩分布广泛,有机质丰度高,资源潜力巨大。基于东缘S区山西组和太原组泥岩主微量元素数据,采用元素地球化学方法,利用多项无机地化指标,对泥岩沉积时期的古气候、古盐度和古氧化还原条件进行了研究。研究表明:①山西组和太原组古气候条件类似,都属于温暖湿润型;②两套地层沉积时期古盐低,属于陆相和海陆过渡相沉积;③山西组和太原组以还原环境和过渡环境为主,太原组沉积环境还原性更强,更有利于有机质富集,TOC丰度更高。因此,除山西组外,太原组也是过渡相页岩气有利勘探层位。

The upper Paleozoic transitional facies shale in the eastern margin of Ordos Basin is widely distributed,with high organic matter abundance and great resource potential.Based on the data of major and trace elements in the mudstone of Shanxi Formation and Taiyuan Formation in s area in the eastern margin,this paper studies the paleoclimate,paleosalinity and paleoredox conditions of mudstone deposition period by using element geochemical method and multiple inorganic geochemical indexes.The results show that:①the paleoclimatic conditions of Shanxi Formation and Taiyuan formation are similar,both of which belong to warm and humid type②The paleosalt of the two sets of strata was low during the sedimentary period,belonging to continental facies and sea land transitional facies③Shanxi Formation and Taiyuan formation are dominated by reducing environment and transitional environment.The sedimentary environment of Taiyuan formation is more reductive,more conducive to organic matter enrichment,and higher TOC abundance.Therefore,in addition to Shanxi formation,Taiyuan formation is also a favorable exploration horizon for transitional facies shale gas.