四川盆地加里东期剥蚀量恢复

Caledonian erosion thickness reconstruction in the Sichuan Basin

四川盆地是一个多旋回叠合盆地，加里东期剥蚀量是下古生界烃源岩热演化、早期油气藏的形成与演化以及下组合资源量计算等研究中不可缺少的基础参数。考虑到剥蚀量恢复方法固有的局限性和适用条件以及四川盆地早古生代时期的沉积构造演化特征，本文在分析了四川盆地志留系的原始沉积范围和下古生界残留地层分布格局的基础上，提出了“沉积速率比值＋古热流反演＋古地质图”法恢复四川盆地加里东期的剥蚀量。志留系原始范围广，覆盖了整个四川盆地，现今川中和川西地区志留系缺失是加里东期剥蚀所致，而不是当时没有沉积。利用钻至下古生界的29口探井的分层数据和130口虚拟井的地震数据，恢复了四川盆地加里东期的剥蚀量，并与古地质图结合，约束了剥蚀量的平面变化趋势。四川盆地加里东期剥蚀量主要受川中古隆起控制，古隆起区剥蚀量为700—1200m，川东和川南地区的剥蚀量一般为100—200m，川北地区的剥蚀量为200—500m。

Sichuan Basin is a multi-cycle superimposed basin. Caledonian denudation plays a key role in the Lower Paleozoic source rock maturation and early reservoir formation and evolution. Considering the inherent limitation of the existing methods of erosion thickness reconstruction and the characteristics of the tectono-sedimentary evolution in the Sichuan Basin we proposed a method of ＂deposit rate ratio＋paleo-heat flow inversion＋ancient geological map＂ to recover the Caledonian erosion thickness based on the analysis of depositional range of the Silurian system and the Lower Paleozoic residual formation distribution pattern. The original Silurian system covered the whole area of the Sichuan Basin. The absence of the Silurian system in the central and western Sichuan Basin is a result of the Caledonian erosion. Using the stratum data of 29 wells drilled the Lower Paleozoic sequences and seismic data from 130 virtual wells, the Caledonian erosion thickness is reconstructed. Combined the erosion thickness data from the boreholes with the ancient geological map, the distribution trend in the spatial is constrained. The results show that Caledonian denudation is mainly affected by the central Sichuan ancient uplift with erosion thickness about 700 - 1 200 m. In the southern and eastern Siehuan Basin, the erosion thickness is generally about 100 - 200 m. In approximately, 200 - 500 m deposits were removed away in the northern Sichuan Basin in the Caledonian tectonic movement.