|Place of Conferral||北京|
|Keyword||青藏高原东南缘 点苍山 炼铁盆地 转换构造 正断层 半地堑 玉龙雪山 虎跳峡 地壳均衡反弹 岩石圈弹性挠曲模型 伸展构造 隆升|
炼铁盆地位于青藏高原东南缘的点苍山西北，是剑川左行走滑断裂与点苍山-罗坪山西坡断裂系的交接部位。通过对该盆地进行详细地层测量和构造变形调查，获得了130多个地层产状，查明近30个断层点位，并统计分析了盆地内砾岩的成分、含量和古水流方向。研究表明，上新世三营组湖相沉积构成该盆地的大部，岩性主要为砂岩、砾岩、泥岩和薄层煤线，其中砂岩占一半以上。盆地沉积物绝大部分可能来源于其西侧的兰坪-思茅盆地。炼铁盆地东侧发育的大型正断层沿平行罗坪山走向（NNW）至少有四级，沿垂直山体走向可以分为四个断裂带。这些正断层控制了盆地的沉积作用，并发育了生长地层。正断作用开始于上新世，并且可能持续到第四纪，磷灰石裂变径迹热年代学分析表明，罗坪山西坡正断层在距今0.15 Ma仍在活动。研究最终得出，炼铁盆地演化可以划分为两个阶段：（一）上新世剑川左行走滑断裂在其南部转换为伸展构造，形成了炼铁半地堑盆地，并且控制了盆地的沉积过程。（二）更新世澜沧江及其支流黑惠江的快速下切，袭夺了炼铁湖盆使其消亡，形成炼铁盆地今日之面貌。 玉龙雪山位于青藏高原东南缘——青藏高原一级地势向云贵高原二级地势的过渡区。它北北西向延伸约60 km，其南部最高峰海拔5596 m，北部哈巴雪峰海拔5396 m，平均海拔约4500 m，高出其周围地区平均海拔近1000 m。雪山顶部存在一个残留剥蚀面，海拔约4250 m。金沙江由南向北从两座雪峰穿流而过，形成著名的虎跳峡。峡谷最大落差3900 m。地质上，该山体的东西两侧被年轻的正断层围限, 形成一个孤立的菱形断块山，与大理地区的点苍山构成一个Z字型地垒的南北两端。玉龙雪山主体是由泥盆纪到二叠纪的一套地层组成，石炭纪的灰岩构成其主峰。根据该区地质地貌特征，我们运用岩石圈弹性挠曲地壳均衡理论，以古残留面为当时金沙江下切玉龙雪山的基准面，研究分析得出，在9-13 Ma金沙江水系快速下切玉龙雪山，造成虎跳峡大规模物质剥蚀时，该山体没有发生差异性隆升,其顶部作为第三纪的剥蚀残山而存在。在晚新生代（5-2.5 Ma），红河右行走滑断裂发生,其北西端转换为伸展构造，玉龙雪山地区发生近东西向伸展，激发了地壳均衡反弹, 峰顶由此隆升了468 m，加大了山体与周围地区的地势高差。而玉龙雪山与周围地区的剩余地势高差主要由构造作用（如正断层）完成，因此晚新生代玉龙雪山的隆升是由构造与侵蚀作用共同控制的结果。玉龙雪山的南东延伸部分——点苍山（4122 m）同样也发生了构造伸展，但是山体没有遭受类似虎跳峡的剥蚀作用，不足以产生相当的均衡反弹 因此其海拔相对要低很多。这进一步证实了地壳均衡反弹导致玉龙雪山隆升，并加大了玉龙雪山与点苍山的地势高差。
Liantie basin is located on the west of the NNW trending Luoping Shan, northwest part of the Diancang Shan with a general definition, at the southeastern margin of the Tibetan Plateau. It is just the place where the left-lateral strike-slip fault of Jianchuan meets the normal faults on the west slope of the Diancang-Luoping Shan. Through detailed measurement of the strata and investigation of structural deformation within the basin, more than 130 of strata attitudes were obtained and about 30 fault sites were discovered and surveyed. Together with the results from statistics of the composition, proportion of conglomerates within the basin and the paleocurrent analyses, the following results has been indicated. The lacustrine sediments of Sanying Formation of Pliocene time comprised most part of the Liantie basin, and rock types within it are sandstone, conglomerates, mudstone and thin coal layers, in which sandstone greatly predominates the components of the sediments, whose source is very likely from Lanping-Simao basin mostly comprised of Mesozoic red beds, to the west of Liantie basin. Bounding the east of Liantie basin, at least four continuing branches of normal faults parallel to, and four fault belts perpendicular to the strike of the NNW trending Luoping Shan, could be observed respectively. These normal faults have controlled the deposition and developed growth strata within the basin. Therefore the normal faulting on the west slope of Luoping Shan, started at the time of Sanying Formation, which is of Pliocence time, and continues to Quaternary. And our apatite fission track analyses indicate that normal faults on the west slope of the Luoping Shan are still active at about 0.15 Ma. The final indication of this work is that the Liantie basin experienced two stages of evolution: (1) Jianchuan left-lateral strike-slip fault, was transformed into extensional structure in its southwestern end in Pliocene time and formed the Liantie basin as a half graben; and the extension has controlled the depositional process of the basin; (2) the Pleistocene rapid incision of Lancang River and its important tributary-the Heihuijiang River (Yangbi River) captured the original Liantie basin, and therefore resulting in the basin from lacustrine close environment into present open system. The Yulong Snow Mountain, NNW trending and 60 km in length, is located in the southeastern margin of the Tibetan Plateau, where is the critical transition zone of topography from the first order (the Tibetan Plateau) to the second order (Yunnan-Guizhou Plateau) in China. The highest peaks on the top of Yulong Snow Mountain are Yulong Peak (5596 m) in the south and Haba Peak (5396 m) in the north. At the top of the mountain, there exists a relatively gentle surface, about 4250 m above sea level, which is considered a relict surface. The average altitude of the mountain is about 4500m, which is ~1000 m higher than that of its surrounding area. The Hutiaoxia (the Tiger Leap Gorge), 3900 m of relief, was just formed just between the two highest peaks. In geological setting, the Yulong Snow Mountain is bounded as a rhombus block by young normal faults, and together with the Diancang Shan within the Dali block composes the two end members of the Z-type horst on the north and south, respectively. The main body of the mountain consists of Devonian through Permian strata and the Carboniferous limestone forming the two highest peaks of the mountain. According to the geologic and geomorphologic characteristics in this area and the elevation of the relict surface (4250 m) referenced as the initial incision surface, the analyses by isostasy of the lithospheric elastic flexural model, indicate that there existed no differential uplift for the Yulong Snow Mountain when the Jinsha River was rapidly incising it during 9-13 Ma and cause the mass lose in the Tiger Leap Gorge, and the mountain was still an eroded relict hill. It is only after the normal faulting was developed at 5-2.5 Ma on both the east and the west sides of the mountain that it triggered the local isostasy within this small area, thereby resulting in the uplift of the snow mountain by 468 m. and the increase of relief between the Yulong Snow Mountain and its surrounding area. But the other relief existing in the two areas is caused by tectonic forcing, such as the normal faulting. Therefore, Late Cenozoic uplift of the Yulong Snow Mountain is controlled by both erosion and tectonic forcing. The Diancang Shan, 4122 m of highest elevation and as the part continuing southward from the Yulong Snow Mountain, was also experienced the tectonic extension at 5-2.5 Ma, but had little erosion like that in the Tiger Leap Gorge, which further prove that the existence of the isostatic rebound occurred in the Yulong Snow Mountain and that this rebound also increased the modern high relief between the two mountains.
|MOST Discipline Catalogue||理学::地理学|
|Table of Contents|
|石许华. 青藏高原东南缘大理地区晚新生代构造地貌过程——以点苍山和玉龙雪山为例[D]. 北京. 中国科学院研究生院,2007.|
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