【摘要】 对商丹盆地茶房村剖面210个样品进行了野外调查及粒度实验分析。结果表明:丹江一级阶地上的沉积物是55 000 a BP以来堆积的风成黄土;粒度特征主要以粉砂和粘粒为主,二者总和为86.65%,其中粗粉砂为优势组分,在剖面中含量达46.81%;粘粒含量为23.94%;古土壤层的粒度组成较黄土层偏细,显示了二者风化成壤作用的差异,即古土壤层风化程度强于黄土层;茶房村剖面粒度特征的变化反映了商丹盆地自55 000 a BP以来区域气候的变化特征:55 000~11 500 a BP时期气候寒冷干燥。全新世早期(11 500~8 500 a BP),气温有升高,降水增加。全新世中期(8 500~3 100 a BP),为大暖期,气候温暖湿润。全新世晚期(3 100 a BP至今),气温降低,降水减少。更多还原

【Abstract】 Loess-paleosol sequences have been applied to retrieve palaeoenvironment change in the study of the paleoclimatic evolution. Chafangcun( CFC) at Shangdan basin,Shaanxi provides such a loess-paleosol profile. At this profile,loess sequence’s color and structure were investigated,and 210 samples were systematically collected for grain-size analysis. The results showed that:(1) Chafangcun loess-paleosol sequence in the first river terrace with typical atmospheric dust sediment along the Danjiang River,has formed since 55 000 a BP.(2) This loess sequence is mainly composed of silt( 5 ~ 50 μm) and clay( < 5 μm),with an average proportion of 86. 65%. The coarse silt of 10 ~ 50 μm in size is dominant composition in CFC profile,accounting for 46. 81% on average,and clay( < 5 μm in size) accounts for23. 94% in total composition. The sequence’s grain-size composition varies from bottom to top stratigraphic unit,and the paleosol is smaller in grain size than that of their loess stratum. These properties reflect that the weathering intensity in paleosol is stronger than in loess.(3) The grain-size characteristics in the Shangdan Basin reveal that the palaeo-climate changed successively in the following four stages: a cold and dry climate during the last glacial( 55 000 ~ 11 500 a BP),a climate from dry & cold to warm & humid during the early Holocene( 11 500 ~ 8 500 a BP),a warm and humid climate during the middle Holocene(8 500~3 100 a BP),and the lower temperature and reduced precipitation climate during the late Holocene(3 100~0 a BP).更多还原