疏勒河冲积扇全新世沉积物粒度特征及其古环境意义

Grain-size Characteristicof the Shule River Alluvial Fan and Its Paleoenviromental Explanation,in Holocene

利用疏勒河冲积扇扇缘十道沟(SDG)剖面沉积物的粒度资料,通过粒度组成、粒度参数、频率累计曲线等粒度特征分析,探讨了疏勒河冲积扇扇缘沉积环境演化过程。分析结果表明,该剖面沉积物颗粒组成主要以粉砂、黏土为主,沉积环境变化频繁。根据粒度参数所反映的古环境意义,将整个剖面沉积序列划分为4个阶段:底部790~500 cm为河湖交替沉积环境,主要以湖沼相沉积为主;500~300 cm为河流相沉积;300~200 cm为河湖交替沉积环境;200 cm^0为河湖交替沉积环境。从而揭示了疏勒河冲积扇扇缘地区13.5 ka.B.P以来沉积环境的演化过程。这些结果对于了解河西走廊西段地区全新世环境演化以及中国西北干旱区未来环境预测方面都具有重要意义。

Located in the northwest and arid area,Shule River Alluvial Fan Oasis is sensitive to climatic and environmental change.The grain-size characteristics of the sediment samples from the Holocene profile at Shidaogou(SDG)in the Shule River Alluvial Fan Oasis are analyzed in this paper,including grain-size distribution,grain-size parameters and cumulative relative frequency curve of grain size.The analysis result indicate that the profile sediment is mainly composed of silty sand clay,and the Sedimentary Environment changed frequently.According to the result of grain-size analysis,the Sedimentary Sequence is divided into four stages:the depth of 790~500 cm is composed of river-lacustrine deposit,mainly composed of lacustrine and swamp deposit;the depth of 500~300 cm is the river deposits;the depth of 300~200 cm is river-lacustrine deposit;and the depth of 200~0 cm is river-lacustrine deposit.Thus that has revealed the Sedimentary Environment process in the margin area of Shule River Alluvial Fan Oasis since13.5 ka.B.P.These results provide valuable information for understanding details of Holocene environment changes and environmental evaluation in the arid area in Northwest China.