西藏冈底斯山脉北坡中更新统拉弄组的发现及其特征

拉弄组剖面位于冈底斯山脉北坡布多藏布拉弄沟 (E84°2 3.5′、N30°37.5′) ,各项条件符合《中国地层指南》关于建组 (层型 )剖面的基本要求。拉弄组为一套弱固结滨湖相碎屑岩 ,顶、底均为 型不整合面 ,厚 85 m左右 ;年代地层单位属中更新统。拉弄组常形成大型峭壁浮雕地貌景观 ,新、奇、特显著 ,因此 ,对拉弄组的研究意义不只限于完善该区第四系地层系统 ,充实高原第四纪古地理格局及环境变迁的分析、研究证据 ,还可为西部旅游业的进一步发展起到有力的推动作用。

ESTABLISHMENT OF THE MIDDLE PLEISTOCENE LALONG FORMATION ON THE NORTHERN SLOPE OF THE GANGDISI MOUNT, TIBET

The stratotype of the Lalong Formation is located in the Lalong groove of Buduozangbu on north slope in Gangdisi Mount, Tibet(E84° 23.5′、N30°37.5′).It is measured in 2001 by the Regional Geological Surveying Institute, Geological Surveying Academy of Sichuan Province. The Lalong Formation, about 85m thick, consists of poorly-indurated clastic rocks of lakeshore facies, its top and bottom having an unconformity of Type I each. It is middle Pleistocene in age. The Lalong Formation ususlly shows a geomorphologic landscape with relief on the cliff face. Thus, the study of it not noly has a significance in the perfection of the Quaternary stratigraphic system of this area, and in the enrichment of the Quaternary paleogeographic framework of the Qinghai-Tibet Plateau and of the evidence for the analysis and study of environmental change, but also gives an impetus to the farther development of the tourism in West China.