南祁连山前区中生代晚期古构造特征的研究

南祁连山前区可以分为露头和盆地区两个不同的大地构造单元,本区晚中生代构造活动强烈,控制了新生代的沉积过程和现今中生界残余层序的分布。本文提出了均匀平板状沉积体后期的构造变形可以利用古地质图以及高精度残余地层厚度的变化规律判断古构造带的分析方法,并且对于研究区中生代晚期的古构造特征进行了分析。露头区主要利用古地质图分析方法,研究区集中在赛什腾山—埃姆尼克山北缘的鱼卡和红山地区。盆地区主要利用中生界残余厚度图的分析方法,研究区集中在赛什腾山—埃姆尼克山南侧的赛什腾南部凹陷和马海凸起地区。通过这4个地区古构造特征的研究,提出南祁连山前区中生代晚期在区域性隆升的背景下,形成了一系列古构造带,古构造活动的特点是形成北西—北北西走向的背斜和向斜构造,这些褶皱的波长为15～20 km,为中尺度规模。同时指出,中国西部多数地区均缺失上白垩统,暗示着当时的中亚地区存在一个广阔的晚白垩世古高原。

Study on characteristics of Latest Mesozoicpaleo-structures in front of south Qilian Mountain,China

The front of south Qilian Mt.can be subdivided into two units:outcrop unit and basined unit,and strong tectonic activities,which controlled depositing process in Cenozoic and distribution of present Mesozoic systems,have occurred in Late Mesozoic in this area.This paper proposed a method for analyzing paleo-structural deformation by paleo-geological maps and changing rules of high resolution residual strata thickness,and studies on paleo-structural characteristics in latest Mesozoic in the study area as well.In outcrop area,paleo-geological maps are mainly used,and Yuqia and Hongshan areas,north of Saishiteng Mt.and Aimunike Mt.,are focused;while in basined area,maps of residual Mesozoic thickness are mainy used,and Saishitengnan depression and Mahai uplift at the south of of Saishiteng Mt.and Aimunike Mt.are focused.Based on analysis for paleo-structural characteristics of above four areas,the paper proposed that there developed a series of paleo-structure belts under the background of regional uplifting in latest Mesozoic at the front of south Qilian Mt.,and those paleo-structures are characterized by NW-NNW-striked anticlines and synclines.whose wavelengths are 15～20 km and middle-scaled.At the same time,the paper also points out that most areas in western China are lack of upper Cretaceous,which implies the existence of a broad Late Cretaceous plateau in central Asia.