A GEOCHRONOLOGICAL STUDY OF THE SALAWUSU STRATA IN NORTH CHINA
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摘要: 我国北方地区晚更新世河湖相标准地层——萨拉乌苏组地层的年代学研究,有助于正确理解萨拉乌苏组与马兰黄土以及与冰期气候对比等关系。笔者近年来根据野外层位对比和地层沉积相的划分,采用同位素年代测定,并结合黄土-古土壤序列研究的最新成果,初步建立了可以与黄土、深海沉积记录和冰期气候波动对比的萨拉乌苏组地层序列。认为河湖相沉积的萨拉乌苏组形成于约140-70kaBP的末次间冰期,大致与深海氧同位素第5阶段对应,与黄土高原古土壤S1发育同期。城川组风成细砂形成于约70-10kaBP的末次冰期,与黄土高原的马兰黄土是同期异相地质体.Abstract: Salawusu Formation in Salawusu river area is one of the standard sections of Late Pleistocene strata in North China.However,there are a lot of different views about the strata since the establishment of Salawusu Formation,especially in the aspects of sedimental facies,stratigraphic age and its climate significance.Here,by the stratigraphic subdivision and dating,the following recognitions can be gained:1.Salawusu Formation is mainly composed of fluvial lacustrine sediments,which corresponds to the stage 5 of deep sea 18O and formed between about 140-70kaBP.Chengchuan Formation mainly consists of fossil aeolian sands with some lacustrine silty-clay in the middle part,which corresponds to the stages 2-4 of deep sea 18O and formed between 70-10 kaBP.Dagouwan Formation is composed of lacustrine sediments and black-paleosol,which formed in early middle period of Holocene with the warm-humid climate,Dishaogouwan Formation consists of sub-loess and aeolian sands,which represented the sedimentation in the cold-dry climate during the late Holocene. 2.As a fluvial-lacustrine sedimentary strata,Salawusu Formation is quite different form its overlying Chengchuan Formation whether in geochronolgy,lithology and sedimentary facies or in palaeontology.Chengchuan Formation and Malan Loess belong to heteropic deposits (sandy and loessic facies) formed contemporaneously under the same wind action. 3.As a fluvial-lacustrine-aeolian-sand sequence found at the Dishaogouwan profile in the Salawusu river area,its climatic records corresponding to that of loess and deep sea deposits,may be divided into 5 climatic periods.It suggests that the climatic change of this region during the last interglacial period is synchronous with that of the whole earth.
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Key words:
- Salawusu Formation /
- dating /
- deep-sea oxygen isotope
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