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| 岩溶夷平面演化与青藏高原隆升 | |
| 引用本文： | 李德文,崔之久.岩溶夷平面演化与青藏高原隆升[J].第四纪研究,2004,24(1):58-66. |
| 作者姓名： | 李德文 崔之久 |
| 作者单位： | 1. 南京大学城市与资源学系,南京,210093 2. 北京大学环境学院,北京,100871 |
| 基金项目： | 国家自然科学基金项目 (批准号 :40 3 0 10 0 4和 40 2 410 11)资助 |
| 摘 要： | 文章以作者在青藏高原南部及东邻地区获得的资料为基础,就青藏高原地区夷平面的识别、整体坡降、时代以及夷平面对构造隆升的响应等问题进行讨论。区域对比与成因分析显示青藏高原石林等形态形成于土下环境,属覆盖型岩溶,而与其共存的红色风化壳(石灰土)具有脱硅富铝作用弱而粘化作用强的特征,与湿热气候条件下的夷平面环境是一致的。根据野外观察资料和岩溶作用对水动力条件的敏感性,岩溶区厚层连续的风化壳只能发育在接近地貌侵蚀基准的夷平面上。因此,厚层连续的风化壳及其壳下的覆盖型岩溶均可指示地貌发育的晚期阶段和夷平面的存在,这为利用覆盖型岩溶及共存的风化壳识别夷平面提供了理论依据。根据青藏高原东邻地区岩溶地貌发育的演化特征,作者认为在同等条件下,岩溶夷平可以在更短的时间里达到更低的夷平高度(相对常态夷平),初步估计岩溶夷平面整体坡降小于0.5‰。构造隆升使青藏高原进入不利于岩溶作用的寒冻圈,岩溶夷平面经刻蚀作用演变为刻蚀平原,而云贵高原刻蚀作用较弱,但受到“土壤丢失”等岩溶过程的破坏。这种差别主要是构造隆升幅度的不同造成的。为了解决夷平面的年代问题,作者对滇西表生锰氧化物40Ar39Ar测年适宜性作了研究,结果显示鹤庆等地表生锰矿具有较 |
| 关 键 词： | 岩溶夷平面 青藏高原隆升 覆盖型岩溶 红色风化壳 刻蚀平原 |
| 文章编号： | 1001-7410(2004)01-58-09 |
| 收稿时间： | 2003-10-28 |
| 修稿时间： | 2003-11-10 |
KARST PLANATION SURFACE AND THE QINGHAI-XIZANG PLATEAU UPLIFT |
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| Institution: | 1. Department of Urban and Resources Sciences, Nanjing University, Nanjing 210093; 2. College of Environment Sciences, Peking University, Beijing 100871 |
| Abstract: | The planation surface provides important evidence for evaluating the uplift ranges and rates of the Qinghai Xizang Plateau. Some results are discussed in this paper on the basis of the recent investigation in the areas of covered karst, the red weathering crust and the karst planation surface in the Qinghai Xizang Plateau and its east adjacent districts, i. e . the Yun Gui Plateau and the Xiang Gui Hill. Based on the genesis research and the regional comparison, the authors discovered that the stone pinnacles in the Qinghai Xizang Plateau was attributed to the covered karst, which formed in subsoil environment and are obviously different from the limestone geomorphologic relief formed in subsurface ones. The characteristics of subsoil solution in the covered karst show the residual properties in the Qinghai Xizang Plateau. Twenty three carbonate weathering crust profiles in the Qinghai Xizang Plateau and its east adjacent districts have been investigated. Some indexes in 23 profiles, such as sa (SiO 2/Al 2O 3), clay mineral type and content, content of the clay sized grains and silt/clay ratios are not obviously different along the changes of altitudes and longitudes. These characteristics may reflect that the original environment was similar. The authors consider that these conditions in large space and time scales can only appear on the late geomorphological stage, i.e . on the planation surface. According to the regional landform evolution characteristics, the authors distinguish karst planation from others and put forward the concept of karst planation surface, which is different from the traditional planation patterns owing to the sloping processes. Essentially, the karst planation process is mainly controlled by the hydrodynamic condition. The authors believe that thick weathering crust in the karst areas can only be developed temporally in the late geomorphologic stage, and spatially on planation surface because of its sensitivity to the groundwater hydrodynamic condition. This theory reflects the relationship between planation surface and weathering crust in karst areas, and provides the theoretical evidence for using covered karst and weathering crust to recognize the planation surface. Based on the analysis of the karst geomorphological evolutions and water system reorganizations, the authors consider further that the basal level of karst planatoin is much lower than that of other alluvial landform. According to the data from the east district, a preliminary estimate is that their original gradient could be lower than 0.5‰, which is lower than that of non karst areas (2‰ by Büdel). Availability of dating of planation surface using 40 Ar/ 39 Ar technique is experimented in the Yun Gui Plateau. Preliminary results indicate that manganese K bearing manganese oxides in Heqing, West Yunnan, have high K content and favorable crystallite, sufficient for pre Quaternary dating. Further work is still in progress. The karst planation surface in the Qinghai Xizang Plateau became etchplain making up of exposed covered karst, such as stone pinnacles, because uplifted environment is unfavorable for karst processes. And the karst planation surface such as the Yun Gui Plateau will be destroyed by “soil loss” if the uplifting continues. The above mentioned spatial differences of the covered karst show a close relationship with the range of the tectonic uplifting. |
| Keywords: | karst planation surface Qinghai Xizang Plateau uplifting red weathering crust etchplain |
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