Abstract: Based on the comprehensive analyses of outcrops,drilling cores,thin sections,and geochemical tests,this study investigates the Shiqianfeng Formation in the Ordos Basin and its adjacent area in terms of rock types,sedimentary structures,sedimentary-facies types,and the spatial distribution of depositional systems. The results revealed that the Shiqianfeng Formation mainly developed alluvial plain,delta plain,delta front,shallow-lacustrine deposits,and the lagoonal and sand-bar deposits in the southern transitional sedimentary environment. During the depositional period of the Shiqianfeng Formation,dry and hot climates,relatively gentle paleogeomorphology,and the high sediment supply gave rise to the formation of a strata interval characterized by fuchsia,brownish-red mudstone,light-gray medium-coarse-grained feldspar lithic sandstone,lithic feldspar sandstone,and feldspar sandstone. In the northern part,the delta is large scale and dominated by braided channel deposits;the associated sands are relatively thick,extensively distributed. However,in the southern part the delta is small scale. During the late depositional period of the Shiqianfang Formation,seawater may have flooded the Linyou-Hancheng-Xiangning area in the south of the basin several times,and developed marine interlayers and sand bar deposits,which to some extent affected the sedimentary environment and sand body distribution.

Key words: sedimentary system, sedimentary facies, late Permian, Shiqianfeng Formation, Ordos Basin

摘要： 基于野外地质露头观察、岩心描述、薄片鉴定和地球化学等分析测试资料的综合分析,对鄂尔多斯盆地及周缘地区上二叠统石千峰组沉积岩石类型、沉积构造、沉积相类型及沉积体系空间展布等方面开展研究。结果表明,石千峰组主要发育冲积平原、三角洲平原、三角洲前缘、浅湖和南部海陆过渡的潟湖、沙坝等沉积环境,石千峰期,古气候干燥炎热,沉积古地形相对平缓,物源供给充足,形成了一套紫红色、棕红色泥岩和浅灰色中粗粒长石岩屑砂岩、岩屑长石砂岩、长石砂岩为主的地层。盆地北部三角洲规模大,以辫状河道发育沉积特征为主,砂体厚度大、横向分布稳定,而盆地南部三角洲规模相对较小。石千峰期,海水可能多次入侵盆地南部麟游—韩城—乡宁一带,发育海相夹层和沙坝沉积,一定程度上影响了南部的沉积环境和砂体展布。

关键词: 沉积体系, 沉积相, 上二叠统, 石千峰组, 鄂尔多斯盆地

CLC Number: 

• P512.2