干旱区湖泊沉积物粒度组分记录的区域沙尘活动历史: 以新疆巴里坤湖为例

根据中国西北干旱区巴里坤湖BLK 1剖面沉积物的粒度分析，采用粒级—标准偏差法提取了对沉积环境变化敏感的粒度组分。结果表明，巴里坤湖沉积物中45～170 μm粒级组分含量和平均粒径对研究区区域性风沙活动较为敏感，据此结合14C测年数据重建了研究区9400 cal aBP以来的风沙活动历史。在过去的2 000年内，巴里坤湖地区尘暴事件多发或强风沙活动时段主要出现在240～440 cal aBP、600～1 280 cal aBP和1 400～1 800 cal aBP期间，这些时段同历史时期的雨土频率高值期、古里雅冰芯阴阳离子高含量期较为一致。从更长地质时期来看，8 000～8 300 cal aBP、7 400～7 700 cal aBP、6 500～7 000 cal aBP时段，特别是在中全新世(3 900～6 100 cal aBP)期间，区域性的尘暴事件或强风沙活动尤其频繁，这些时段同古里雅冰芯中微粒浓度、敦德冰芯中的微粒含量记录均可以进行良好的对比。干旱区封闭湖泊沉积是记录地质历史时期风沙活动的良好载体，但由于气候环境变化往往具有较强的区域性特征，因此，对某一剖面沉积物环境敏感粒度组分的提取及应用不具有普适性。

Variations in Dust Event Reflected by Grain-size Component of Lacustrine Records in Droughty Area:a case study on Barkol Lake, Xinjiang, China

Grain size analysis of BLK 1 section, retrieved from Barkol Lake, NW China, was carried out using a Malvern 2000 grain size analyzer, and environmentally sensitive grain size components can be easily identified according to the variations in the grain size standard deviation. The results indicated that 45~170 μm grain size component and its mean grain size diameter are sensitive to the regional dust events in the study area, combined with the radiocarbon ages, the dust events during the last 9.4 cal ka BP was reconstructed. During the last 2 000 years, strong dust events appeared at 240～440 cal aBP, 600～1 280 cal aBP and 1 400～1 800 cal aBP epochs, which are consistent well with the high values of rain dust frequency and high contents of ions in Guliya Ice Core. During the last 9.4 cal kaBP, 8 000～8 300 cal aBP, 7 400～77 00 cal aBP, 6 500～7 000 cal aBP, especially during the middle Holocene epoch of 3 900～6 100 cal aBP, the regional dust events took place continually, which can contrast well with the microparticulate records in Guliya and Dunde Ice Cores. Lacustrine sediment in droughty areas is a good carrier which can denote the dust events during the historical period well, as the climatic variations has great regional characteristics, and so the environmentally sensitive grain size components in some one section could not be used universally.