弥渡、巍山盆地中更新世地质特征及其演化

【作者】 马宏杰；

【导师】 张世涛；

【作者基本信息】 昆明理工大学 ， 地质工程， 2010， 硕士

【摘要】 弥渡、巍山盆地位于扬子准地台(Ⅰ)和唐古拉—昌都—兰坪—思茅褶皱系(Ⅳ)两个一级构造单元的接合部位,大地构造位置极为特殊。弥渡盆地位于红河断裂带的北东处,巍山盆地位于红河断裂带的南西处,两盆地属于走滑拉分盆地。本文以弥渡、巍山盆地各阶地沉积物为研究重点,并对其进行热释光测年,来分析山脉的隆升速率、盆地的形成演化和沉积环境演变等情况。通过野外调查,发现在弥渡、巍山盆地之间的山脉两侧发育了各种类型的阶地,其沉积物主要为更新统松毛坡组(Qps),岩性主要为灰、灰黄、紫、紫红色中—厚层状砾岩、砂砾岩、砂岩为主,夹灰黑、灰白、褐色粘土岩、粉砂岩和数层煤层。阶地类型为基座阶地。弥渡盆地共发育五级阶地,其分布情况为：Ⅰ级阶地主要分布于盆地西侧冷官营-小家营-奇家营一带,高程在1690m-1750m之间,热释光测年值为200.48±22.05Ka；Ⅲ阶地主要分布于盆地西侧大红箐-龙华寺-三甲村-三合中村一带,高程在1750m-1830m之间,热释光测年值为239.06±26.30Ka,隆升速率为0.23m/ka；Ⅳ阶地主要分布于盆地西侧平安庄、大纪罗、三合上村等地,高程在1900m-2100m之间,热释光测年值为320.85±35.29Ka,隆升速率为0.59m/ka；V阶地分布于盆地西侧大树坪、小纪罗、天目山等地,高程在2150m-2250m之间,热释光测年值为332.07±36.59Ka,隆升速率为0.042m/ka。巍山盆地共发育四级阶地,其分布情况为：Ⅰ级阶地主要分布于盆地南侧的热水塘处,其高程为1661m,根据热释光测年为118.64±13.05Ka,隆升速率为0.134m/ka；Ⅱ级阶地在盆地西侧分布于南山村-向旭下村-向阳中村一带,盆地东侧分布于黄乐村-瓦窑村一带,热释光测年值为137.23±15.09K,隆升速率为0.25m/ka；Ⅲ级阶地主要分布于盆地东侧的新村-河上湾-东厂-小禾里-谢家村-琪盘山-石龙山一带,呈狭长条带分布,高程在1750m-1900m之间,热释光测年值为258.52±28.44Ka,隆升速率为1.46m/ka；Ⅳ级阶地主要分布于盆地东侧的李青元、小黄草坝、黄草坝等地,高程在2050m-2200m之间,热释光测年值为511.35±56.25Ka,隆升速率为0.86m/ka。通过对山脉隆升速率的分析可知：巍山盆地与弥渡盆地之间的分水岭地带形成于50万年来的差异性升降运动,两侧隆升速率基本相当,而且表现出早期快速隆升,晚期隆升速率减缓的趋势。根据以上分析可知弥渡盆地共有5次间隙隆升阶段,巍山盆地共有4次间隙隆升阶段。弥渡盆地发展演化阶段：(1)332.07±36.59Ka至320.85±35.29Ka期间为湖泊相沉积,气候温和,浅水等环境；(2)：320.85±35.29Ka至239.06±26.30 Ka期间为洪积扇堆积-河流相-浅湖-半深湖-浅湖-沼泽-三角洲相的沉积环境,共分两个旋回。(3)：239.06±26.30 Ka至200.48±22.05Ka期间为湖泊近岸沉积;(4)200.48±22.05Ka至10Ka期间为湖泊近岸-沼泽-河湖相-湖泊近岸-浅湖-湖泊近岸的沉积环境。巍山盆地演化阶段：(1)：511.35±56.25Ka至258.52±28.44Ka期间为洪积扇沉积。其沉积相从下往上依次为洪积扇(扇根)-洪积扇(扇中)-洪积扇(扇端)-河流沼泽相沉积,气候温和,植被茂盛。(2)：258.52±28.44Ka至137.23±15.09Ka期间为河流相沉积。(3)：137.23±15.09Ka至118.64±13.05Ka期间底部为湖泊近岸-沼泽相沉积,往上出现3个洪积扇(扇根)-洪积扇(扇中)-洪积扇(扇端)由细变粗的进积型的反旋回层序,说明当时盆地处于紧缩状态；(4)：118.64±13.05Ka至lOKa期间为河流相沉积。弥渡、巍山盆地属于走滑拉分盆地,是在红河断裂带右旋走滑拉伸作用下形成的。更多还原

【Abstract】 Midu and Weishan basins are located in the joint unit of Yangzi quasi-floor (Ⅰ) and Tanggula--Changdu--Lanping--Simao fold lines(Ⅳ), whose tectonic location is extremely complex. Midu basin is located in the North East of the Red River fault zone. Weishan basin is located in the South West of the Red River fault zone, and both two basins belong to slip pull-apart basins.In this paper, Midu and Weishan basin sediments are to study and to gain thermo luminescence dating, and to analyze the uplift rate of the mountains, sedimentary basin formation, evolution of environmental changes and so on.Through a field survey, we discover that in Midu and Weishan basins, on both sides of the mountains between Midu and Weishan mountains, various types of terraces grow, and it is mainly Pleistocene sediments from the loose hair slope Group (Qps) and litho logy is mainly grey, grey-yellow, purple, purple-thick layered rocks, gravel, sandstone and clip-black, gray, Brown clay, rock, siltstone and the amount of the seam. Terraces type is the base terraces.There are totally five development terrace levels among Midu basin, and its distribution is:level I terraceis located to the West of Lengguanying-Xiaojiaying-Qijiaying,the elevation is about 1690m to 1750m, and the TL dating value is 200.48±22.05Ka;level III terrace is located to the West of Dahongqing-Lonhhuasi-Sanjiacun-Sanhezhongcun, the elevation is about 1750m to 1830m, the TL dating value is 239.06±26.30Ka, uplift rate is 0.23m/ka; level IV terraces are mainly located in the basin to the West of Pingan Village, Daluoji and Sanheshang Village. The elevation is about 1900m to 2100m, the TL dating value is 320.85±35.29Ka, uplift rate is 0.59m/ka; level V terrace is on the West side of Dashuping, Xiaoluoji and Tinmushan.The elevation is about 2150m-2250m, the TL dating value is 332.07±36.59Ka, and uplift rate is 0.042m/ka.There are totally four development terrace levels among Weishan basin, and its distribution is:level I terrace is located to the south of Reshuitang, the elevation is about 1661m, and the TL dating value is 118.64±13.05Ka;level IIterrace is located to the West of Nanshancun, xiangxuxiacun, xiangyangzhongcun, the TL dating value is 137.23±15.09Ka, uplift rate is 0.25m/ka; levelⅢterraces are mainly located in Xincun, heshangwan, dongchang, xiaoheli, xiejiacun, qipanshan, shilongshan. The elevation is about 1750m-1900m, the TL dating value is 258.52±28.44Ka, uplift rate is 1.46m/ka; level IV terrace is on the east side of Liqingyuan, xiaohuangbacun, huangbacun. The elevation is about 2050m-2200m, the TL dating value is 511.35±56.25Ka, and uplift rate is 0.86m/ka.Through the uplift rate analysis:Weishan basin and Midu basin watershed areas are between the difference of 50 million years to lifting movement, both sides uplift rate is pretty basic and show a rapid rise early, and a rate slowed later.According to the above analysis shows the Midu basin, a total of 5 time gap uplifting stage, and as to Weishan basin, there are 4 time gap uplifting stage.Midu basin development evolution stages:(1) of 332.07±36.59Ka to 320.85±35.29Ka period for lake sediments, mild climate, shallow water environments such as; (2):320.85±35.29Ka to 239.06±26.30 Ka period for pluvial stacked-fluvial-on the Lake-deep lake-Lake-swamp-Delta phase of depositional environments, divided into two cycles. (3): 239.06±26.30 Ka to 200.48±22.05Ka Lakes coastal deposition during; (4) of 200.48±22.05Ka to 10Ka Lakes coastal-during swamp-Lake and river-lake shore-on the Lake-Lake shore sedimentary environments.Weishan basin evolution stages:(1):511.35±56.25Ka to 258.52±28.44Ka period of alluvial fan deposits. The sedimentary facies were from the bottom up alluvial fans (fan root)- alluvial fans (fan in)-alluvial fans (fan side)-River marsh facies, mild climate, lush vegetation. (2):258.52±28.44Ka to 137.23±15.09Ka period of fluvial deposits. (3):137.23±15.09Ka to 118.64±13.05Ka during the bottom of the lake shore-swamp facies, up there three alluvial fans (fan root)-alluvial fans (fan in)-alluvial fans (fan side) into the product by the fine thicken the type of anti-cyclic sequences, indicating that basin in a tight state; (4): 118.64±13.05Ka to 10Ka period of fluvial deposits.Midu and Weishan basins are strike-slip pull-apart basin, basin, is dextral strike-slip fault zone in the Red River formed under tension.更多还原