河南南召盆地上三叠统太山庙组软沉积物变形构造及其古地理意义

Soft-sediment deformation structures from the Upper Triassic Taishanmiao Formation of the Nanzhao Basin in Henan Province and their palaeogeographic significances

河南南召盆地上三叠统太山庙组中发现的软沉积物变形构造包括同沉积断层、液化均一层与泄水脉、底劈构造、塑性变形层、碎裂岩及大型负载构造。它们集中保存在太山庙组中段深湖环境中,以该层段为界,其下水体渐深,其上水体渐浅。多数软沉积物变形构造与浊流沉积砂体相伴生,也可保存在泥岩层中,其形成可能与浊流沉积过程相关,但古地震活动是主要的触发机制。软沉积物变形的类型包括液化变形、塑性变形和脆性变形,指示了高强度的古地震活动,记录了秦岭造山带印支期一次强烈的造山活动。造山带逆冲推覆作用造成南召盆地的抬升,代表了前陆盆地系统中的楔顶沉积。

A lot of soft-sediment deformation structures,including synsedimentary faults,liquefied homogeneous layers and water escape veins,diapirs,plastic deformation,cataclasites and large load structures,occurred in the Upper Triassic Taishanmiao Formation of the Nanzhao Basin in Henan Province. They mainly cluster together in the middle part of deep lacustrine deposits,which is the transitional zone between the lower deep water and the upper shallow water. Most of the soft-sediment deformation structures are preserved in turbidites,except for the synsedimentary faults in shales. The major trigger mechanism of the soft-sediment deformation structures is the palaeoearthquake,although the depositional process of turbidite may play a role. The liquefied,plastic and brittle deformation structures are considered as the indicater of the high magnitude palaeoearthquake,which record the intense orogenic movements of the Qinling orogen during the Late Triassic. With the thrusting of the Qinling orogen,the Nanzhao Basin was uplifted,whereas the synchronous Jiyuan Basin,adjacent to the north,was subsided. They most likely represent the wedgetop depozone and the foredeep depozone of the foreland basin system respectively.