摘要
泌阳凹陷作为国内典型的陆相断陷咸化湖盆,在古近系核桃园组三段广泛发育细粒沉积岩.文中利用长井段连续取心资料以及薄片观察、二维XRF扫描、XRD分析、扫描电镜以及地球化学测试等手段,以矿物组分、沉积构造和粒度作为主要依据,把泌阳凹陷H3Ⅲ亚段细粒沉积岩划分为9种岩相类型,其中纹层状混合质页岩、纹层状长英质页岩是发育类型最多的细粒沉积岩;通过Mg/Ca、Al含量、Ti含量、(Fe+Al)/(Ca+Mg)、P/Ti、Sr/Ba和V/(V+Ni)等地球化学指标的垂向变化及岩相组合来分析沉积环境的演化特征.泌阳凹陷H3Ⅲ亚段沉积环境是半深湖—深湖环境,水体盐度为半咸水—咸水,陆源输入总体较强,气候变化相对较大,从下到上经历了干旱、干湿交替、湿润以及干旱的气候变化.岩相的垂向变化受气候、陆源输入、水深、水体盐度的影响,气候、陆源输入、水深决定了长英质矿物和黏土矿物的含量,而碳酸盐矿物的含量主要受到水体盐度和气候的影响.
Abstract
Fine-grained sedimentary rocks widely developed in the third Member of Paleogene Hetaoyuan Formation in Biyang Sag,a typical continental rift-subsidence saline lacustrine basin in China.With the use of continuous core data of long well sections,thin section observation,two-dimensional XRF scanning,XRD analysis,scanning electron microscopy and geochemical testing data,this paper divided the fine-grained sedimentary rocks of H3 Ⅲ submember in Biyang Sag into nine lithofacies types on the main basis of mineral composition,sedimentary structure and grain size.Among them,laminated mixed shale and laminated felsic shale are the most developed types of fine-grained sedimentary rocks.The evolutionary characteristics of sedimentary environment are analyzed through the vertical changes of geochemical indexes such as Mg/Ca,Al content,Ti content,(Fe+Al)/(Ca+Mg),P/Ti,Sr/Ba,and V/(V+Ni)and the lithofacies combination.The sedimentary environment of H3 Ⅲ submember of Biyang Sag is a semi-deep lake to deep lake environment,with its salinity being semi-saline to saline water.The terrestrial inputs are strong in general,and the climate change is relatively large.From bottom to top,it has undergone climate changes of drought,drought-wetting alternation,wetting,and drought.The vertical change of lithofacies is influenced by climate,terrestrial inputs,water depth and water salinity.The climate,terrestrial inputs and water depth determine the contents of felsic minerals and clay minerals,and the content of carbonate minerals is mainly influenced by water salinity and climate.
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