利用古温标恢复四川盆地主要构造运动时期的剥蚀量

地层剥蚀量是沉积盆地埋藏史和热史重建中一个关键的参数.本文利用石油钻井的系统古温标(Ro)资料,并结合多种恢复方法,得出四川盆地主要构造运动时期的剥蚀量.研究表明:加里东期,川东南剥蚀量较大,达2000m.东吴运动时期,川西南、川东南等距二叠纪玄武岩喷发区较近地区的剥蚀量较大,分别在260～450 m和800～900m:印支早期盆地整体遭受了抬升剥蚀作用,剥蚀厚度为100～500 m.印支中、晚期龙门山地区褶皱剥蚀,H1、Y1等钻井该时期的地层剥蚀量超过2000 m.燕山期周缘山系的继续隆升造成山前大范围地区的剥蚀:喜山期盆地周缘钻井的剥蚀量较大,在2000 m左右,而早期古隆起上的钻井如GJ、J13、Z12等钻井的地层剥蚀量则较小,在1000 m左右.可见,四川盆地不同地质时期及不同构造区位的剥蚀厚度都不尽相同,这一时空差异反映了构造运动对该区的差异影响.这一研究也表明,以系统的古温标资料(R_o)为基础,针对不同地质情况选用适当的反演方法并结合多种反演方法.能有效地恢复钻井在不同时期的剥蚀量.上述四川盆地各时期剥蚀地层厚度的恢复,对研究该区的构造、沉积和油气演化提供了基础数据.

Quantifying the denudations of major tectonic events in Sichuan basin: Constrained by the paleothermal records

Based on the paleo -thermal indicator of vitrinite reflectance (Ro), the authors reconstructed the denudation thickness of the sedimentary formation in the boreholes of Sichuan basin. The largest denudation occurred in southeastern Sichuan basin and reached 2000m in Caledonian period. During Dongwu movement, the denudation reached the values of 260～450m in southwestern Sichuan basin and reached 800～900m in southeastern Sichuan basin. Both areas were close to the central zone of Emeishan basalts. The basin was uplifted in early Indosinian period, and the denudation thickness reached 100～500m. In middle and late Indosinian period, the areas around the Longmen Mountain began to be denudated, and the denudation thickness in boreholes of these areas reached the values of over 2000m. In Yanshanian period, the areas around the mountains beside Sichuan basin experienced variable degrees of denudation due to the uplifting of these mountains. According to the inversion results of many boreholes, the maximum denudation occurred in areas close to the basin boundary and reached 2000m in Himalayan period. However, the areas which were uplifted in the early time were subjected to less denudation, and the values only reached 1000m or so.