燕山地区燕山期的挤压与伸展作用

燕山地区中生代断裂演化、区域性不整合界面和盆地演化的地质事实显示,燕山期不仅存在强烈的挤压作用,而且存在强烈的伸展作用。如果把整个侏罗、白垩纪期间的构造运动理解为燕山运动的话,那么燕山运动既形成强烈褶皱和逆冲推覆,又形成断陷盆地和变质核杂岩。整个燕山运动(旋回)包括3次挤压事件和3个伸展阶段,即早侏罗世末挤压事件(北票组沉积之后,海房沟组沉积之前)、晚侏罗世末挤压事件(土城子组沉积之后,义县组沉积之前)和白垩纪末挤压事件(第三系沉积之前);早侏罗世盆地伸展阶段、中晚侏罗世盆地伸展阶段和白垩纪盆地伸展阶段。燕山期内发生了3次由伸展到挤压的转换。

Yanshanian compression and extension in the Yanshan area

The Mesozoic faults,regional unconformities and basin evolution in the Yanshan area suggest that there occurred not only strong compression but also strong extension in the Yanshanian Stage.If the tectonic movements that took place in the entire Jurassic and Cretaceous are included in the Yanshanian movement ,then this movement gave rise to not only strong folding and overthrusting but also down-faulted basins and metamorphic core complexes.The entire Yanshanian movement comprises three compres-sion events and three extension phases.The former are the compression event at the end of the Early Jurassic(after the deposition of the Beipiao Formation and before the deposition of the Haifanggou Forma-tion),compression event at the end of the Late Jurassic(after the deposition of the Tuchengzi Formation and before the deposition of the Yixian Formation)and compression event at the end of the Cretaceous (before the Tertiary deposition);the latter are the extension phases for the development of the Early Jurassic basin,Mid-Late Jurassic basin and Cretaceous basin.The three compression events were shorter,corresponding to the durations of the formation of their related unconformities,while the extension phases of the development of three basins were longer,corresponding to the durations of the basin evolution in the three phases.Three transformations from extension to compression took place in the Yanshanian Stage.