滇西北丽江地区湖盆地质环境特征及其演化分析

发布时间：2018-03-22 10:41

本文选题：滇西北　切入点：丽江　出处：《成都理工大学》2015年硕士论文　论文类型：学位论文

【摘要】：丽江盆地位于滇西北地区丽江市,是一个新生代的断陷盆地。其西侧紧邻滇西名山”玉龙雪山”,玉龙雪山发育着北半球纬度最低的山岳冰川。金沙江从盆地北部大具盆地穿过。盆地呈近南北走向,长约31km,北部宽约3-6km,南部宽约11km。丽江盆地在构造位置上处于川滇菱形地块中部,活动断裂发育。本文主要以滇西北地区丽江盆地为研究对象,进行详细的野外地质调查,对盆地第四纪沉积物的分布范围、沉积物类型、相互关系等进行详细的路线地质调查及关键地质点调查,对关键的沉积物出露地进行剖面测制。结合对断裂的野外观测,分析了盆地的发展演化过程。取得如下主要认识:通过对盆地沉积物的岩性、结构、构造以及沉积环境等分析,确定了丽江盆地的沉积类型以及分布范围。冰前期蛇山组主要分布在盆地南部蛇山公园一带,是一套以粘土夹细砂和砾石层的河湖相沉积。玉龙雪山产生的两期冰碛物分布在盆地北部,均为山岳冰川类型,主要为一套混杂堆积的砾石,夹有巨大的漂砾,砾石成分以玄武岩为主。现代湖相沉积分布在盆地西南部,其更早时候的分布范围达到了丽江城西部及东部山麓地区,主要为一套湖沼沉积。现代河流相沉积分布在盆地中部以及偏北地区,分布范围正在不断向南扩张,主要为一套河流相砾石层。通过对盆地周边断裂的野外调查,发现玉龙山东麓断裂并不是单一的正断层性质,野外擦痕表明其并存着逆冲和走滑性质。在拉市海东南部和丽江城北黑龙潭公园新发现北西-南东向构造,该方向构造在蛇山组中有明显的反映。拉市海蛇山组发育倾向北东的正断层,在蛇山组沉积时期也有该方向正断层的影响,发育同沉积正断层。蛇山组受该方向构造作用影响发生褶皱作用,轴面向下北西。很可能是北西-南东向构造作用导致蛇山组沉积中断,发生构造抬升,接受剥蚀作用。综合丽江盆地周边断裂性质及断裂组合样式、沉积物形态、沉积速率,丽江盆地的性质为走滑-拉分盆地。
[Abstract]:Lijiang Basin is located in Lijiang City, Northwest Yunnan. It is a Cenozoic faulted basin. The west side of the basin is next to the famous mountain Yulong Snow Mountain in western Yunnan. The Yulong Snow Mountain has the lowest latitude in the Northern Hemisphere. The Jinsha River passes through the basin from the northern part of the basin. The basin is nearly north-south strike. The Lijiang basin is about 31km in length, 3-6km in the north and 11km in the south. The Lijiang basin is located in the middle of the Sichuan-Yunnan rhombic block and the active faults are developed. Detailed route geological survey and key geological site survey are carried out on the distribution range, type and interrelation of the Quaternary sediments in the basin, and the key sediment outcrops are profiled, combined with the field observation of the faults. The development and evolution of the basin are analyzed. The main conclusions are as follows: through the analysis of the lithology, structure, structure and sedimentary environment of the sediments in the basin, The sedimentary types and distribution range of Lijiang basin are determined. It is a set of fluvial and lacustrine facies deposited in clay with fine sand and gravel. The two periods of moraine produced by the Yulong Snow Mountain are distributed in the northern part of the basin, both of them are of mountain glacier type, mainly a set of mixed and accumulated gravel with huge drift gravel. The gravels are mainly basalts. The modern lacustrine deposits are distributed in the southwest of the basin, and their earlier distribution ranges to the western and eastern foothills of Lijiang City. The modern fluvial facies deposits are distributed in the central and northward regions of the basin, and the distribution range is continuously spreading southward, mainly a set of fluvial gravel beds. Through field investigation of the faults around the basin, It is found that the Yulong Shandong foot fault is not a single normal fault, and the field scratches indicate that the faults coexist with thrust and strike-slip properties. NW-SE trending structures were newly discovered in the southeast of Lashi Hai and the northern Heilongjiang Lake Park of Lijiang City. This direction structure is obviously reflected in the Shishan formation. The normal fault of the Lashi Haishishan formation tends to be northeastward, and it also has the influence of this direction normal fault during the sedimentary period of the Sheshan formation. A synsedimentary normal fault is developed. The Shishan formation is affected by this direction of tectonism, and the axis faces to the lower north west. It is very likely that the NW-SE tectonic process caused the sedimentary interruption and tectonic uplift of the Seshan formation. The characteristics of faults and fault assemblages, sediment morphology, sedimentation rate, and strike-slip pull-apart basin are synthesised in Lijiang Basin.
【学位授予单位】：成都理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P56

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