酒泉盆地南缘新生代冲断带的变形特征和变形时间

Deformation characteristics and time of Cenozoic thrust belt in southern margin of Jiuquan basin

酒泉盆地南缘冲断带具有多层次的逆冲结构,包括浅层的远距离冲断系统、中层的近距离冲断系统和深层的原地冲断系统。远距离冲断系统由奥陶系和志留系构成,局部地区表现为飞来峰;近距离冲断系统由古生界和中生界构成,大部分隐伏在远距离冲断系统之下,局部地带以构造窗的形式出露地表,其变形样式主要为叠瓦状的冲断变形;原地冲断系统隐伏在近距离冲断系统和第四系之下,其南部的变形主要表现为双冲构造或堆垛构造,往NE方向变形逐渐简单,主要表现为断层传播褶皱和断层弯曲褶皱,前锋地带表现为三角带的突起构造。酒泉盆地南缘冲断带的变形是一个具有大缩短量的薄皮冲断系统,旱峡剖面的构造缩短量为52.7 km,缩短率为55.1%。酒泉盆地南缘冲断带的变形时期大致开始于9.0 M a,并以“前展式”向北扩张,变形时间向北变新,前锋断层开始活动时间约为8.3 M a。

The multi-layer thrust belt in the southern margin of Jiuquan basin consists of a long distance shallow thrust system, a short distance middle thrust system, and a deep in-situ thrust system. The long distance thrust system is composed of Ordovician and Silurian and some part of it shows as a klippe. The short distance thrust system that hides under the long distance thrust system and locally crops out as a structural window is composed of Paleozoic and Mesozoic and has the deformation style of imbricate structure. The in-situ thrust system, with duplex or stacking structure in its south, a simpler deformation of propagation fold and fault-bend fold in its northeast, and a pop-up in its front, is under the short distance thrust system and the Quaternary. The thrust belt in the southern margin of Jiuquan basin occurs as a thin-skinned thrust system with a large structural shortening of 52.7 km and a shortening rate of 55.1% on the Hanxia section. Deformation of the thrust belt started at about 9 Ma and extended northward progressively, with faulting beginning at 8.3 Ma in the front of thrust belt.