川中—川西北加里东期古隆起对比研究

A comparative study of the central Sichuan paleo-uplift and the northwest Sichuan paleo-uplift during Caledonian period

四川盆地加里东期经历了桐湾、郁南、都匀、广西等多期次构造运动,于盆地中西部和西北部分别形成了川中古隆起和川西北古隆起。重建加里东期川中古隆起和川西北古隆起形成演化过程及其关联性可以为四川盆地中西部和西北部深层海相层系下一步油气勘探部署提供新思路。本文通过对四川盆地已有钻井和地震资料的分析,开展了不同构造区的震旦系—早古生代地层对比分析,识别出四川盆地加里东期古隆起各套地层尖灭点分布范围、不整合削截点和上超点。利用地震、连井剖面相结合的方法,重塑了川中和川西北地区古隆起的形成演化过程。综合研究认为,加里东期古隆起的构造形态在晚奥陶世—早志留世初步形成,在晚志留世广西运动中经历了细微调整,古隆起在早志留世达到最大展布范围,于二叠纪沉积前定型,郁南运动和都匀运动对加里东期古隆起的变形起着重要作用;二者总体经历了“隆-凹”分异阶段(Z—∈_(1)m)、隆起定型阶段(∈_(1)q—S_(1))、联合隆升阶段(S_(2)—C)、稳定埋藏阶段(P—T_(2))等4个阶段。

The Caledonian paleo-uplifts in the Sichuan Basin are mainly located in the mid-west and northwest parts of the basin.Reconstructing and analyzing the formation and evolution of the Caledonian Middle Sichuan paleo-uplift and the northwest Sichuan paleo-uplift can provide new insights and perspectives for the future oil and gas exploration in the Sichuan Basin.Based on the results of the published borehole and seismic data,this study has carried out comparative analyses of the stratigraphic features between the middle and northwest parts of the Sichuan basin,and then identified the distribution of the pinching point,unconformity truncation point,and onlap point for each layer of the Caledonian paleo-uplift in the Sichuan Basin.On this basis,using seismic profiles and cross well lines,we have detailedly depicted and reconstructed the formation and tectonic evolution process of Caledonian paleo-uplifts in the Sichuan Basin.The evidence shows that the Caledonian paleo-uplifts were initially formed from the Late Ordovician to the Early Silurian,and they were slightly readjusted during the Late Silurian Hanjiadian period.The paleo-uplifts reached their maximum distribution range in the Early Silurian and finalized before Permian.The Duyun Movement and the Yunan Movement in the region were key tectonic movements affecting the formation of Caledonian paleo-uplifts in the Sichuan Basin.It is concluded that the Caledonian paleo-uplifts in the Sichuan Basin mainly experienced four stages of tectonic evolution:the differential uplift-fall stage(Z—∈_(1)m),the developmental stage(∈_(1)q—S_(1)),the denudation and flattening stage(S_(2)—C),and the stable burial stage(P—T_(2)).