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通过对西藏海拔最高、面积最大的纳木错湖周缘的第四纪环境演变调查研究与1:25万当雄幅区域填图工作,在环纳木错沿岸发现了一种与湖泊演化有关的湖相沉积岩石——湖滩岩。本文首次对纳木错周缘发育的湖滩岩进行了描述。从湖滩岩水准仪测定的保存高度看,它已构成1.5～8.3m、8.3～15.6m、14～19.9m、18.7～25.8m等四级较明显的湖滩岩阶地。湖滩岩由亮晶砂屑藻凝块灰岩、泥晶白云质砾岩和方解石胶结含砾岩屑砂岩等组成,岩石具粗砂状、含砾砂状、角砾状结构,块状构造,基底式胶结。其铀系全溶样品的等时线年龄测定结果表明,湖滩岩形成于18.7±3.8～29.3±2.7ka BP的晚更新世中晚期。本文根据岩矿鉴定,并结合沉积相、岩相组合等特征,探讨了湖滩岩的形成机理。为研究该区湖泊演化、气候变化、古地理变迁及第四系划分等提供了新资料。
Through the investigation on the Quaternary environmental evolution around the Nanmu Lake with the highest elevation and the largest area in Tibet, and the mapping of 1: 250000 males, a lacustrine sedimentary rock related to lake evolution was found along the coast of the Nemoku Lake - Beach Rocks. This paper describes for the first time the lacustrine rocks developed along the margin of Nam Co. Judging from the preservation height measured by the lake beach rock level, it has formed the obvious lake beach rock terraces of 1.5 ~ 8.3m, 8.3 ~ 15.6m, 14 ~ 19.9m and 18.7 ~ 25.8m. The lagoon rocks are composed of bright sand and algal clinker limestone, dolomitic dolomitic conglomerate and calcite cemented conglomerate rock. The rocks are gritty, pebble-bearing, brecciated, block-like Base-type cementing. The results of isochron age determination of uranium isotopes showed that the bank rocks formed in the late Late Pleistocene from 18.7 ± 3.8 ~ 29.3 ± 2.7 ka BP. Based on the identification of rock and mine and the characteristics of sedimentary facies and lithofacies assemblage, this paper discusses the formation mechanism of lake and beach rock. It provided new information for studying the lake evolution, climate change, palaeogeographic change and Quaternary division in this area.