柴达木盆地北缘西段侏罗纪原型盆地研究

发布时间：2018-03-30 14:44

本文选题：侏罗纪　切入点：物源分析　出处：《西北大学》2017年硕士论文

【摘要】：侏罗系是柴达木盆地北缘地区重要的烃源岩层和煤系地层。受多期复杂构造运动的改造破坏,目前对柴北缘侏罗系原型盆地和原始沉积面貌认识薄弱,存在诸多争议,制约了该区油气勘探和对基础地质演化的认识。论文在借鉴前人研究成果的基础上,以改造盆地的研究思路为指导,采用露头剖面观测,地震与钻井测井资料分析,以及多方法物源分析等手段,对柴北缘侏罗系开展了地层划分对比、沉积相分析、物源综合分析等研究,取得以下主要认识:受后期剧烈构造改造的影响,研究区侏罗系分布复杂,呈叠合深埋、抬升剥露等多种赋存状态。下侏罗统主要分布于冷湖-南八仙构造带以南,中、上侏罗统分布于该带以北。盆地覆盖区与赛什腾山分布的中侏罗统具有较好的可对比性。通过露头、钻井沉积相分析,认为研究区侏罗系主要发育辫状河、辫状河三角洲、扇三角洲、湖泊等沉积相类型。大煤沟组主要发育辫状河三角洲平原和三角洲前缘亚相,晚期普遍发育半深湖相沉积,仅少数露头或层段可见边缘相沉积。通过对研究区样品轻重矿物、岩屑、砾石成分、碎屑锆石年龄等统计分析,认为研究区西部早侏罗世主要物源区为阿尔金山,其次为北缘隆起区;中、晚侏罗世物源主要来自南祁连,其次为北缘的局部古隆起。根据地震资料解释及沉积相剖面,结合区域地质资料,认为柴北缘侏罗纪盆地经历了:早侏罗早期小型断陷与坳陷并存、早侏罗世中期-中侏罗世的伸展坳陷以及晚侏罗世的挤压坳陷3个演化阶段。早侏罗世小型断陷盆地主要发育在昆特伊凹陷,坳陷型盆地主要发育在伊北凹陷;中侏罗世坳陷盆地主要发育在赛什腾山-鱼卡凹陷及苏干湖凹陷;晚侏罗世挤压坳陷盆地沉积范围缩小,向柴北缘东部迁移。综合地层特征、沉积相特征、物源特征及周缘山系隆升时限的分析认为,早侏罗世原始盆地沉积边界大致为:西到阿尔金南缘山前,东部、北部边界在冷湖-南八仙构造带以北,南部边界存疑;中侏罗世原始盆地边界大致为:西界、南界在冷湖-南八仙构造带以南,北界在祁连山南缘断裂带,东界为鱼卡东、绿梁山山前。
[Abstract]:Jurassic is an important source rock and coal measure strata in the northern margin of Qaidam Basin. Due to the alteration and destruction of multiple complex tectonic movements, the understanding of the prototype basin and original sedimentary features of Jurassic in the northern margin of Qaidam Basin is weak and controversial. This paper, based on the previous research results, takes the research ideas of reforming the basin as the guidance, adopts outcrop profile observation, seismic and drilling logging data analysis. The stratigraphic classification and correlation, sedimentary facies analysis, and provenance comprehensive analysis of Jurassic in the northern margin of Qaidam are studied by means of multi-method provenance analysis. The main conclusions are as follows: influenced by the severe structural transformation in the late stage, The distribution of Jurassic in the study area is complex, with multiple occurrence states, such as superimposed deep burying, uplift and exfoliation, etc. The Lower Jurassic is mainly distributed south of the Lenghu-Nanbaxian structural belt, in the middle. The upper Jurassic is distributed in the north of the belt. The basin overlying area has a good contrast with the Middle Jurassic system distributed in the Seston Mountains. Through outcrop and drilling sedimentary facies analysis, it is concluded that the Jurassic in the study area mainly developed braided rivers and braided river deltas. Fan delta, lacustrine and other sedimentary facies. The braided river delta plain and delta front subfacies are mainly developed in Dawangou formation, and semi-deep lacustrine facies are generally developed in the late period. Only a few outcrops or strata can be seen as marginal facies deposits. Based on the statistical analysis of the samples of heavy and heavy minerals, lithic rocks, gravel compositions, and zircon ages, it is concluded that the main source of early Jurassic in the western part of the study area is Aljin Mountain. The middle and late Jurassic provenances mainly came from South Qilian, followed by local paleouplift in the northern margin. According to seismic data interpretation and sedimentary facies profile, combined with regional geological data, It is considered that the Jurassic basin in the northern margin of Qaidam experienced the coexistence of small faults and depression in the early Jurassic period. The extensional depression from the middle to the middle Jurassic and the compression depression from the late Jurassic are three stages of evolution. The small fault basins of the early Jurassic are mainly developed in the Kunteyi depression, and the depression basins are mainly developed in the Yibei sag. The middle Jurassic depression mainly developed in the Saishitengshan-Yuka sag and Sugan Lake sag, and the sedimentary area of the late Jurassic compressional depression basin was reduced and migrated to the east of the northern margin of Qaidam. Based on the analysis of provenance characteristics and uplift time of the peripheral mountain series, it is concluded that the sedimentary boundary of the early Jurassic primitive basin is roughly: from west to the southern margin of Altun, in the east, the northern boundary lies north of the Lenghu-Nanbaxian structural belt, and the southern boundary is doubtful; The boundary of the middle Jurassic primitive basin is roughly: the west boundary, the southern boundary is south of the Lenghu-Nanbaxian structural belt, the north boundary is the fault zone of the southern margin of Qilian Mountains, the eastern boundary is Yukadong and the front of the Liliang Mountains.
【学位授予单位】：西北大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P618.13

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