佳木斯-伊通断裂带大型逆冲构造带的发现及形成时代

吉林省四平市石岭新发现的佳木斯-伊通断裂带大型逆冲构造带,其逆冲断裂、碎裂岩和褶皱构造十分发育。佳-伊断裂带东、西两条主干边界断裂附近次级断裂密集分布、褶皱构造以较紧闭的直立褶曲为主,相反在断裂带中部断裂和褶皱稀少、地层产状平缓,反映主干边界断裂是挤压应力集中地带。断裂大部分向南东110°～130°方向逆冲。根据逆冲断裂与中、新生代地层之间的切割、覆盖关系,认为佳-伊断裂在白垩纪以来至少发生两期强烈的逆冲作用:第一期逆冲作用即大型逆冲断裂带的形成时代是晚白垩世晚期;第二期发生在渐新世末期。结合野外调查和盆地资料,将佳-伊断裂的构造演化分为左旋走滑(K₁早期)、区域伸展(K₁晚期-K₂早期)、挤压逆冲(K₂晚期)、断陷(E)和挤压反转(E₃末期)5个阶段。

Discovery and timing of major thrustbelt in Jiamusi-Yitong fault zone

The newly discovered major thrustbelt in the Jiamusi-Yitong fault zone in Siping city of Jilin province has well developed thrusts,cataclasite,and folds.In areas near the eastern and western main boundary faults, secondary faults are distributed intensively,and folds are dominated by closed vertical bends,while in the central part of the thrustbelt,the strata occurrence is gentle with few faults and folds,indicating that the main boundary faults are the area of compressive stress concentration.Most of the faults thrust towards the 110°-130° irection.According to the relationship of cutting and overlaying between the thrusts and the Mesozoic-Cenozoic strata,the Jiamusi-Yitong fault zone is considered to have experienced at least two periods of strong obduction since the Cretaceous:the first occurred in late Late Cretaceous,when the major thrustbelt was formed;and the second occurred at the end of Oligocene.According to field survey results and basin data,the formation and evolution of Jiamusi-Yitong fault zone can be divided into five stages:namely sinistral strike-slip(early K₁),regional stretch(later K₁-early K₂),compressive and thrusting(late K₂),fault depression(E),and compressive inversion(the end of E₃).