摘要
本文介绍了青藏高原东北部地区的古喀斯特现象，并对相关沉积进行了化学成分、粘土矿物的Ｘ－射线衍射以及石英砂表面结构等气候代用指标的分析。分析结果一致，指示了温暖湿润的亚热带气候条件。重结晶方解石的裂变径迹测年结果（１５－８ＭａＢＰ）表明，该地区古喀斯特发育于中中新世。后期随着青藏高原的抬升，原先覆盖型喀斯特遭剥蚀而裸露成地表喀斯特，并演化成目前仍保留着的状态。
The widespread distribution of karst landforms in the limestone area of Qinghai-Xizang Plateau in China has attracted attentions from geomorphologists. The preliminary study in the nonheast area of the Plateau indicates that the main types of karst include pinnacle karst, clints, limestone wall, cave and 'widow-like cave', and etc.The results of fission track (FL) dating of recrystalized calcites in karst caves are 15.70 MaBP,12.19 MaBP,11.68 MaBP and 10.57 MaBP respectiwly(Tab. 4),Which are all in the mid-Miocene Epoch.The results from the analysis of relevant deposit,which is relic terra rossa or red regolith,reflect a kind of subtropical climate. The vahe of SiO2/Al2O3 is about 3.30 (Tab.2),which is similar to that of the soils under subtropical. climate. X-ray diffraction analysis indicates that the average content of kaolimte in caly minerals is over 20%(Tab.3),even over 50% in some samples(such as Hx and Lms-1 and Mc-2). The quartz sand grains were studied under the ebctronic scanning microscope(SEM), some chemical modification features (Fig.2) on the grain surface indicate that the terra rossa was formed under warm and humid climate.Two main reasons contribute to the karst evolution in this area, they are the uplift of QinghaiXizang Plateau and the northwards shift of latitudinal zone since the Pliocene. The karst evolutioncan be divided into 3 slages(Fig.3),the first stage:intense karst process,the second stage:coutinning karst process, and the third stage: mechanical weathering and relic karst process.
出处
《地理学报》
CSSCI
CSCD
北大核心
1996年第5期408-417,T001,共11页
Acta Geographica Sinica
基金
国家自然科学基金
关键词
青藏高原
古喀斯特
风化壳
环境演变
喀斯特地貌
Qinghai-Xizang Plateau, Polaeokarst,Red regolith, Environment evolu tion
