下扬子地区沿江前陆盆地形成的构造控制

Tectonic Contral on Development of the Foreland Basin along the Yangtze River in the Lower Yangtze River Region

华北板块与扬子板块沿大别—胶南造山带的陆-陆碰撞,使造山带南侧的扬子板块成为前陆变形带,并在其上发育了沿江前陆盆地。沿江前陆盆地初始继承性发育于下扬子区海退末期残留的拗陷区,随后于黄马青期(T_3)受北界滁河断裂与南界江南断裂的对冲控制而成为双向压陷型盆地。在象山群下段(J_1)沉积时,由于江南隆起带的强烈抬升,沿江前陆盆地向北迁移。至象山群上段(J_2)沉积时,沿江前陆盆地开始萎缩,成为彼此孤立的小盆,直到消亡。沿江前陆盆地中黄马青群(T_3h)与下伏地层、象山群(J_(1-2)x)与黄马青群及象山群与上覆地层之间的角度不整合,代表了前陆发生了3次强烈的挤压变形,也反映了华北板块与扬子板块3次强烈的碰撞活动。

Owing to continent -continent collision along the Dabie-Jiaonan orogenic belt between the North China and Yangtze plates, the Yangtze plate south of the orogenic belt became a foreland deformation belt, and a foreland basin along the Yangtze River was developed on the foreland belt. The foreland basin firstly appeared in a depression region which remained in the Lower Yangtze region during retrogression. The foreland basin became a double - pressioned basin probably controlled by back thrusting along the Chuhe and Jiangnan boundary faults in the Huangmaqin period (T3). During deposition of the lower Xiangshan Group (J1), intense uplift of the Jiangnan uplift belt perhaps made the foreland basin migrate toward the north. During deposition of the lower Xiangshan Group (J1), the foreland basin shrank and became small separated basins before disappearance of the foreland basin. Angular unconformities between the Huangmaqin Group (T3h) and underlying strata, the Xiangshan (J1-2x) and Huangmaqin (T3h) groups as well as the Xiangshan Group (J1-2x) and overlying strata represent three intense compression deformation, and also possibly reflect three intense collision between the North China and Yangtze plates.