再论罗布泊“大耳朵”地区的干涸时间

Rediscussion on the latest drying up of the "Great Ear" in the Lop Nor area

在收集前人考察成果及各类遥感影像基础上，通过实地调查，对罗布泊“大耳朵”地区干涸时间获得若干新认识。经过对1958年航片重新解译，认为根据1958年航测资料估绘，于1963年出版的罗布泊1：100000地形图在“大耳朵”地区标注地物属性不正确，1958年干涸的环状盐壳地貌已经形成，未被洪水淹没。盐沙包…Cs分析结果表明，高约1m盐沙包自上世纪50年代以来含^136Cs堆积层仅表层9cm，证明1958年“大耳朵”未被洪水淹没。“大耳朵”地区干盐湖盐壳粉砂含量高达10％-30％，如此大量风尘堆积的存在，也说明其形成不可能在4—5年内完成。土壤下层湖积淤泥HC测定结果表明在剖面F01处全新世早、中期均为水淹没并植物茂盛，最上层位于深105cm处淤泥距今3000余年。罗布泊“大耳朵”地区除“耳心”在20世纪30年代还有水覆盖外，其余广大盐壳区主要是在全新世晚期，由西向东逐渐干涸，完成由淡水湖-半成水湖-成水湖-盐湖-干盐湖的转变。

Based on the previous survey results, various remote sensing imagery, and authors＇ field investigation, a few new understandings on the timing of the latest drying up of the ＂Great Ear＂ in the Lop Nor area were achieved. A reinterpretation of the 1958 aerial photographs completed suggest that the official topographic maps derived from the 1958 aerial photographs for the study area are incorrect in properties of several surface features. The concentric salt crust landform was already in place prior to the 1958 great flood and only a small portion of the area of the ＂Great Ear＂ was flooded. 137Cs isotope dating results show since 1950＇ s only 0 -9cm surface soil had deposited that reject the hypothesis that the ＂Great Ear＂ in the Lop Nor area was formed by rapid drying up of the 1958 flood water within 4 to 5 years during the early 1960＇ s. And the high sediment concentration of salt crust rejects the formation only 4 -5 years also. 14C isotope dating results at the 105 cm deep puddle soil layer of profile H）I shows its age more then 3 000 a. It means during the early and mid Holocene there were immersed by water and plant growth thickly. Except for the inner part of the ＂Great Ear＂ which was still covered by lake water in 1930＇ s, the widespread slat crust area within the ＂great Ear＂ area was formed during the late Holocene （3 000 a B P）. The ＂Great Ear＂ experienced the fresh water lake-semi saline lake-saline lake-sah lake-dry salt lake stages.