资源环境学院知识库

青藏高原内、外缘新生代沉积盆地敏感地记录了印度—亚洲板块碰撞后高原隆升历史和变形机制。位于高原东北缘的酒西盆地属板块碰撞效应的最北响应地区，新生代地层沉积演化记录了高原扩展过程和阿尔金断裂活动历史。本文通过对酒西盆地最西端红柳峡西剖面新近系（疏勒河组）河湖相沉积物古地磁和岩石磁学研究，结合剖面沉积环境分析及前人在盆地不同位置的研究结果，明确了剖面疏勒河组磁性地层年代，探讨了盆地演化与青藏高原北部隆升、阿尔金断裂活动的关系，获得以下成果：1）红柳峡西剖面疏勒河组和玉门砾岩组地层发育，可划分为浅湖相、扇三角洲相、河流相和洪积扇四种沉积相；2）热退磁和岩石磁学实验结果显示，岩石特征剩磁主要由磁铁矿、磁赤铁矿及少量赤铁矿携带，次生剩磁主要由针铁矿携带，部分绿色样品可能含胶黄铁矿；
3）红柳峡西剖面疏勒河组记录了24个正磁极性带和24个负磁极性带，磁性地层年代为17.8 - 4.5 Ma；4）6.7 Ma以前红柳峡西古水流向南流，酒西盆地主要受北部阿尔金断裂控制，6.7 Ma后盆地主要受祁连山北缘断裂控制，并导致盆地自此逆时针旋转了6°；5）盆地不同位置地层沉积特征显示，中新世北祁连山西段并不是整体隆升，中中新世晚期（～13 Ma）中部老君庙开始逐步抬升，构造应力不断向西传播并于晚中新世（6.7 Ma）到达山体最西端红柳峡西，自此古水流向北流，北祁连山西段开始整体隆升，上新世（～5 Ma）起急剧快速隆升至现今高度。

Sedimentary deposits in the interior and outside of the Tibetan Plateau archive the uplift history attributed to the Cenozoic India-Asia collision. The Jiuxi Basin, located in the northeastern of Tibetan Plateau and junction region between Altyn Tagh Fault and North Qilian Fault, is the most ideal region to research this northerly response to the collision effect, the process of northward growth of Tibetan Plateau and the activity history of Altyn Tagh Fault. In this study, new Neogene section, the west Hongliuxia section, is researched by sedimentary facies and magnetostratigraphy. The magnetostratigraphic data combined with basin evolution and previous studies. This study discussed the tectonic uplift of North Qilian Shan and activity of Altyn Tagh Fault during the middle Miocene to early Pliocene.1) The Shulehe Formation and the Yumen Conglomerate Formation can be subdivided into four facies, we identified the facies in the Shulehe Formation as shallow lacustrine, delta fan, fluvial facies, the Yumen Conglomerate Formation as alluvial fan system.2) The demagnetization and rock-magnetism experiments show that characteristic remanent magnetization (ChRM) is mostly carried by a combination of magnetite and maghemite, and hematite is second one. The goethite is secondary remanent magnetization carrier.3) We identified 24 normal magnetic chrons (marked as N1 - N24) and 24 reverse magnetic chrons (marked as R1 - R24) in west Hongliuxia section, with each magnetozone defined by two or more specimens. Magnetostratigraphic correlation suggest that the Shulehe Formation spans from 17.8 Ma to 4.5 Ma.4) Paleocurrent direction indicate the river of the west Hongliuxia flowed southwardly before 6.7 Ma, and the Altyn Tagh Fault controlled the tectonic evolution of Jiuxi Basin. The North Qilian Fault controlled initially tectonic evolution of the basin after 6.7 Ma. In addition, paleomagnetic declination results from the section indicate 6 degree counterclockwise rotation of the Jiuxi Basin since 6.7 Ma.5) Rather than integral growth of the western part of North Qilian Shan. The Laojunmiao region, located in the central part, is earliest uplift gradually in the middle Miocene (~13 Ma). The tectonic force propagated along the North Qilian Fault from east to west Hongliuxia until late Miocene (6.7 Ma), and paleocurrent flowed northwardly. The whole North Qilian Shan occurred rapid uplift since the early Pliocene (~5 Ma).