【作者】 张广良；

【导师】 张培震； 柴炽章；

【作者基本信息】 中国地震局地质研究所 ， 构造地质学， 2006， 博士

【摘要】 青藏高原东北缘地区是晚新生代以来高原隆升并向北持续扩展的最新变形前缘地带,形成了特有的“盆-山”地貌格局和环境演化,大规模陆内逆冲-褶皱造山系的强烈隆升,相关盆地东西向串珠排列,环境的变化也反映在沉积物的变化上,从东部的六盘山,沿着祁连、河西走廊、昆仑一直到中国西部的天山,第三系的红层沉积是高原北部特有现象。因此,青藏高原东北缘因其所处的构造位置而成为解决青藏高原隆升和周边造山带造山过程的关键地区。青藏高原东北缘位于海原断裂带东段的六盘山-马东山地区属于中新生代典型挤压逆冲造山带,相关盆山构造变形历史具有连续变形和周期性脉动的特征,中新世以来该造山带前缘寺口子盆地和后缘隆德盆地为典型前陆盆地,造山作用过程和盆地沉积演化具有盆山耦合特征,盆地中地层层序齐全,沉积了巨厚的陆相沉积物,保存着大量的高原隆升远程效应、陆内碰撞造山过程以及构造变形的大量信息,通过这些记录使得我们可以揭示、反演出构造变形历史,探索构造变形空间迁移和不同构造之间的转换平衡关系,重塑青藏高原东北缘变形和隆升历史,详细探讨该区在整个青藏高原在向北扩展过程中造山带和盆地之间动力学过程。通过对六盘山-马东山地区造山带和相关盆地区域地质背景、沉积学特征、磁性地层、生物地层、沉积相和构造层序及构造变形序列和样式的综合分析,系统探讨了研究区盆山演化的动力学过程,主要获得的以下认识:六盘山-马东山逆冲褶皱造山带的前缘和后缘分布着不同类型的盆地,寺口子盆地沉积特征表明它是该造山带前缘的一个典型前陆盆地,而六盘山后缘隆德盆地在第三纪时期是一个逆冲挤压走滑性质盆地,二者尽管在成因上有所不同,但是其沉积特征具有非常类似的特征,属于同一造山带上的不同产物。寺口子剖面地层出露齐全,因此本文将寺口子剖面作为研究的重点,并系统采集了古地磁样品,对其进行了详细的磁性地层分析,寺口子剖面沉积主要属于中新世以来的新生代沉积,地质时代由老至新进行重新划分和标定,由老至新依次为寺口子组划归为早中新世沉积（N₁¹）,其顶界年龄与清水营组底界约有1.53Ma沉积间断,底界年龄大约为18.02Ma;清水营组划归为中中新世沉积（N₁²）,地质时代在10.97-14.9Ma之间;红柳沟组属于晚中新世沉积（N₁³）,时代间隔为5.28-10.97Ma;马家庄组为早上新世沉积（N₂¹）,沉积时代为3.60-5.25Ma之间;干河沟组为晚上新世沉积（N₂²）,地质时代为1.77-3.60Ma之间;老庄组相当于更新世沉积（Q₁）,沉积时代大约在0.2-1.77Ma之间。上述划分与早期划分差别较大,在六盘山-马东山地区早期可能并不存在始新世和渐新世沉积,可能原因是早期高原隆升并向北扩展效应导致该区遭受逆冲挤压造山作用使山体抬升出现沉积间断而导致始新世和渐新世沉积地层缺失。隆德盆地是六盘山-马东山褶皱逆冲造山带后缘典型盆地,其沉积特征和岩石地层与前缘盆地寺口子盆地具有十分类似的特征,隆德剖面中寺口子组大致相当于早中新世沉积（N₁¹）,清水营组的沉积时代大致相当于中中新世（N₁²）,红柳沟组相当于晚中新世（N₁³）的沉积,顶界年龄不会晚于8Ma。根据区域地层对比,本文海原地区的清水营组、红柳沟组和干河沟组在年代学确定和分析上与寺口子盆地和隆德盆地是完全不同的概念,其时代主要限制在渐新世-中新世之间,其间缺失了晚中新世-更新世之间的地层,直到第四纪时期才开始继续接受沉积,结合贺家口子磁性地层结果,由南西向北东较老地层保存逐渐完整,更多还原

【Abstract】 The northeastern margin of the Tibetan plateau is the frontier of the northeastward expanding Tibetan plateau since the late Cenozoic. This region is characterized by a structural pattern of“basin and range”which was formed during the uplifting and outward expanding process of the Tibetan plateau in the late Cenozoic era. Mountains controlled by fold and thrust belts uplift strongly, and separate the widespread Cenozoic basin into many smaller basins with thick Cenozoic deposits. The Cenozoic stratum of the northeastern Tibetan Plateau is spectacular, distributed from the Liupanshan, via the Hexi corridor, Qilianshan and Qaidam, to the Tianshan. Since the Oligocene all these areas are characterized by thick, nearly continually deposited layers. The Cenozoic layers not only record the environment change, but preserve detailed information about the Cenozoic tectonic deformation also. Therefore, the northeastern Tibetan Plateau is an ideal region for the resolution of problems, such as the uplifting history of the Tibetan Plateau.The Liupanshan-Madongshan, which is located on the eastern segment of the Haiyuan fault zone is a typical Mesozoic and Cenozoic compressive thrust mountain belt. The correlative sedimentary and orogenic evolvement have the character of continous deformation and periodic pulsatory mountain-building in the basin-and-range coupling system,To the north, the Sikouzi basin is a typical foreland basin and the trailing-edge Longde bansin is a representative basin with thrusting and strike-slipping since the Miocene. The development of these basins is coupled with the uplifting of the surrounding mountains. The basins are filled with thick terrigenous deposits which record detailed information about the uplifting of the Tibetan plateau, intracontinental collision and relevant Cenozoic deformation. Deciphering of these records will help illuminate the history of Cenozoic deformation, migration of deformation, relationships among different structures, and the histories of deformation and uplifting of the whole northeastern margin of the Tibetan plateau.Based on integrated analyses of the regional geologic setting, depositional characteristics, paleomagneto-stratigraphy, bio-stratigraphy, sedimentary facies, tectonic sequences, and sequences and styles of the Cenozoic deformation, many interesting results are obtained, and the evolution process of the mountains and basins of the studied region are discussed. Main results of this thesis are summarized below:Different types of basins developed in the front of and behind the Liupanshan-Mandongshan fold and thrust mountain belt. The Sikouzi basin in front of the mountain is a typical foreland basin, while the Longde basin, which lies at the back of the Liupanshan, is a compressive, strike-slip related basin.The Sikouzi section is emphasized in this study. Along this section systematic paleo-magnetic samples are collected and analyzed. The results show that most of the layers were deposited since the Miocene. According to the paleomagnetic ages, formations on this section are divided and calibrated, and six formations are recognized. The lowest Sikouzi formation is the early Miocene（N₁¹）with the bottom age of 18.02 Ma, and there is a 1.53Ma disruption of the deposition更多还原