阿联酋迪拜中部沙漠沉积物粒度特征及其沉积环境分析

Analysis of grain-size characteristics and sedimentary environment of sediments in central Dubai,United Arab Emirates

沙物质粒度特征是分析粒度组成演变过程、判别沉积环境的重要参考。采集阿联酋迪拜中部沙漠152个不同地貌部位地表沉积物,对其化学成分、粒级级配、粒度参数进行系统分析,并根据Sahu经验模型和概率累积曲线判断沉积环境。结果表明:1)研究区沙物质的CaO和SiO2含量较高(61.75%~70.91%);2)除丘间平地外,优势粒级为中沙、细沙和极细沙(1~4Φ);分选中等、较好或好;粒度频率曲线近对称、正偏或负偏分布,中等宽峰、窄峰或极窄峰态。丘间平地含有砾石较多(21.36%),分选差;粒度频率曲线呈现极负偏,极宽峰;3)沉积物以悬移和跃移质为主,环境低能且稳定。古沙丘全部为风成沉积,丘间平地多为洪流沉积,砂岩既有风成沉积也有水成沉积,与野外调查结果相符。

The grain-size characteristics of sediments is a significant reference for analyzing the evolution process of grain-size composition and distinguishing sedimentary environment.152 samples of surface sediments at different geomorphological sites in central Dubai,United Arab Emirates(UAE),were collected,chemical composition and grain-size parameters were systematically analyzed,and the sedimentary environment was judged according to the Sahu experience model and the probability cumulative curves.The results show that:1)The content of CaO and SiO2 in the study area is higher(61.75%~70.91%).2)In addition to the flat land between hills,the dominant grain sizes of sediments in different geomorphic positions are medium sand,fine sand and very fine sand(1~4Φ),being moderately,well or very well sorted.The frequency curves show nearly symmetrical skewness,negative skewness or positive skewness,and showing mesokurtic,leptokurtic or extremely leptokurtic.At the flat terrain,the content of gravel(22.42%)is higher.Sediments are poorly sorted,with frequency curves being extremely negative skewness and extremely platykurotic.3)The sediments are mainly saltation and suspension load,which indicates a low-energy and stable environment.The fossil dunes are aeolian deposits;most of the flat terrains are flood deposits;the sandstones have both aeolian deposits and fluvial or delta deposits,which is consistent with the field observation.