鄂尔多斯盆地东南部下二叠统山西组二段物源体系及沉积演化模式

发布时间：2018-09-17 18:25

【摘要】：早二叠世是鄂尔多斯盆地海陆变迁的关键时期,其中下二叠统太原组沉积期由于发育稳定的碳酸盐岩地层,其陆表海沉积环境得到了大多数学者的认可,而对于下二叠统山西组的沉积环境与沉积体系的认识则存在着较大的争议。为此,在研究该盆地东南部区域构造背景与周缘古陆特征的基础上,结合岩石、重矿物与稀土元素的组成特征,分析了该区山西组二段(以下简称山2段)的物源体系,并依据地层、古生物、沉积构造、古盐度等分析结果,判别其沉积环境并建立了沉积演化模式。结果表明:(1)山2段沉积期发育南、北两大物源体系,其中北物源主要来自古阴山褶皱造山带,南部物源则来自祁连—北秦岭造山带,延安南部宜川—富县一带是上述两大物源的交汇区;(2)该区自早二叠世太原末期—山西早期发生区域性海退,海水自东南方向退出,山2段沉积期仍受到海侵作用的影响;(3)延安以北地区发育三角洲沉积体系,其以南地区则发育障壁岛海岸沉积体系;(4)该区山西组沉积在平面上具有"岸线频繁迁移,水体影响范围广"的特点,垂向上多套储集砂岩体与泥岩、煤层频繁交替转换,形成了良好的源储配置关系。
[Abstract]:The early Permian is the key period of the sea and land vicissitude in the Ordos Basin. The sedimentary environment of the Taiyuan formation of the Lower Permian is recognized by most scholars because of its stable carbonate strata. However, the understanding of sedimentary environment and sedimentary system of Shanxi formation of Lower Permian is controversial. Therefore, on the basis of studying the regional tectonic setting and the paleocontinent characteristics of the southeastern part of the basin, combining with the composition characteristics of rocks, heavy minerals and rare earth elements, the provenance system of the second member of Shanxi formation (Shan 2) in this area is analyzed. According to the results of stratigraphy paleontology sedimentary structure paleosalinity and so on the sedimentary environment is distinguished and the sedimentary evolution model is established. The results are as follows: (1) there were two major provenance systems in the sedimentary period of the second member of the mountain, of which the north source mainly came from the paleoyin mountain fold orogenic belt, the southern source came from the Qilian-north Qinling orogenic belt, and the south source came from the Qilian-north Qinling orogenic belt The Yichuan-Fuxian area in the south of Yan'an is the confluence area of the two major provenances. (2) from the late early Permian to the early Shanxi, the regional sea retreat occurred in this area, and the sea water retreated from the southeast. The sedimentary period of Shan 2 member is still influenced by transgression. (3) delta sedimentary system is developed in the north of Yan'an area, and the coastal sedimentary system of barrier island is developed in the south area. (4) the deposit of Shanxi formation in this area has frequent migration of shoreline on the plane. Because of the wide influence of water body, vertical multiple sets of reservoir sandstone body and mudstone, coal seams frequently alternately change, forming a good relationship between source storage and distribution.
【作者单位】：陕西延长石油(集团)有限责任公司;陕西省陆相页岩气成藏与开发重点实验室;陕西延长石油(集团)研究院;
【基金】：国家科技重大专项“鄂尔多斯盆地东南部页岩气成藏规律与有利勘探区评价”(编号:2011ZX05008-004-70) 陕西省科技统筹创新工程计划项目(编号:2012KTZB03-03)
【分类号】：P618.13

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