摘要
青藏高原第四纪大陆冰盖形成的各种各样冰川遗迹,分布十分广泛。是重建和研究古大陆冰盖最有力的证据。目前发现和比较肯定的冰蚀遗迹有:冰蚀平原、冰蚀丘陵、U形谷、冰蚀洼地、冰盆、冰阶、冰笕、冰坡和基岩鼓丘等。冰碛遗迹主要有:块砾碛、鳍碛(新类型)、漂砾碛(新类型)、冰水砂砾岩、和冰碛丘陵、冰台及侧碛堤等。从大陆冰盖遗迹分布连续和普遍发育,证明青藏高原在第四纪时期曾形成连绵一片的统一的大陆冰盖。大陆冰盖形成的时期为早更新世,形成时的古雪线的海拔高度最多在2000m左右,冰川类型属于海洋性统一大陆冰川。
Preliminary study indicates that various glacial remnants of the Quarternary continental glacial sheet on the Qinghai-Xizang (Tibet) Plateau are distributed very widely and developed continuously. The remnants that have been discovered and confirmed are as follows: glacial erosion landform: ice-scoured plains, icescoured hills, U-shaped valleys, ice-scoured basins, ice-scoured depressions, glacial staircases, glacial chutes, glacial slopes and bedrock drumlins; glacial drift remnants: moraines, block-moraines, fin-shaped moraines (new type), boulder moraines (new type), morainic hills, glacial tables and lateral moraine bars. The remnants of the continental glacial sheets are preserved the best in the interior drainage area, while they are rare and even disappear in the exterior drainage area and the areas where mountain glaciers have developed since the middle Pleistocene. Based on the continuous and wide distribution of the continental glacial sheet, it is considered that the Quarternary continental glacial sheet in the Qinghai-Xizang Plateau is a unified continental glacial sheet. This continental glacial sheet has some characteristics usually found in oceanic glacier. It largely formed in the middle Early Pleistocene. The center of the unified continental glacial sheet lies in the middle part of Xizang at lat. 32-35°N and long. 81-89°E. At the center the ice flows run radially from the center outwards, but in other places the ice flows mostly run from west to east. The thickness of the unified continental glacial sheet is at least 1000—1500 m. It is inferred that the snow line in the middle Early Pleistocene is about 2000 m above sea level.The determination of the Quarternary unified continental glacial sheet in the Qinghai-Xizang Plateau not only of practical and theoretical significance for gaining a better knowledge of the Quarternary glaciation in China and the world, clarifying the evolution of paleoclimate, discussing the existence of the Quarternary glaciers in the east part of China, studying the machanism for the uplift of the Qinghai-Xizang Plateau and constructing some engineering projects, but also the south boundary of the Quarternary continental glacier in the world can be pushed from about lat. 40°N to lat. 28°N according to this determination.
出处
《地质论评》
CAS
CSCD
北大核心
1989年第5期468-478,共11页
Geological Review
