印度河-恒河平原风成黄土的发现及其意义

发布时间：2018-04-20 02:29

本文选题：印度河-恒河平原 + 黄土　；参考：《中国科学:地球科学》2017年02期

【摘要】：风成黄土堆积包含了丰富的古气候演化信息,如中国黄土古环境研究在过去几十年取得了重要进展.目前在印度地区黄土研究大都集中于其北部喜马拉雅山南坡的Kashmir地区,其他地区很少见到风成黄土的报道.通过对印度新德里-安格拉-斋普尔地区平原沉积物的地貌地形及沉积物地层的野外观察,发现其与大部分中国黄土古土壤序列相似,地层之间为过渡的渐变关系,不具有河流冲积物层理,且发育着明显的土壤层次,说明印度河-恒河平原很有可能存在未被识别的风积黄土古土壤序列.为了进一步确定其存在性,本文对位于印度河-恒河平原的一处疑似黄土堆积进行了采样及室内分析,结果表明代表性样品的粒度分布及稀土元素(REE)的配比模式与中国黄土极为相似,同时代表性样品的单颗粒石英扫描电镜(SEM)图像显示出新鲜的贝壳状断口、丰富的撞击圆麻点、机械撞击形成的碟型坑等风尘颗粒具有的特征.此外,环境磁学与岩石磁学实验表明,样品中的主导磁性矿物为亚铁磁性的磁铁矿及磁赤铁矿,可能含有少量的赤铁矿,并且其常温磁学参数与中国黄土具有很好的可比性.综合以上结果,我们认为印度河-恒河平原地区广泛分布着风成黄土堆积,且黄土的存在可能促进了印度农耕的发展,从而推动印度古文明的兴起与繁荣.这也为日后对该地区地层中蕴含的古气候信息解读提供了新的更成熟的研究载体.
[Abstract]:Eolian loess accumulation contains abundant paleoclimate evolution information, such as the study of loess paleoenvironment in China has made important progress in the past few decades. At present, most of the loess studies in India are concentrated in the Kashmir area on the southern slope of the Himalayas in the north of India, and there are few reports of eolian loess in other regions. The geomorphological topography and sediment stratigraphy of the plain sediments in the Delhi-Angla-Jaipur area, India, are observed in the field. It is found that they are similar to most of the loess paleosol sequences in China, and there is a gradual transition relationship between them. There is no fluvial alluvial stratification and obvious soil layers which indicate that there is an unrecognized sequence of aeolian loess paleosols in Indus Ganges Plain. In order to further determine its existence, a suspected loess deposit in the Indus Ganges Plain is sampled and analyzed in laboratory. The results show that the grain size distribution and the REE (rare earth element) matching pattern of the representative samples are very similar to those of Chinese loess, and the single grain quartz scanning electron microscope (SEM) images of the representative samples show fresh shell fracture and rich impact circle points. The characteristics of dust particles such as disk pits formed by mechanical impact. In addition, environmental magnetics and petromagnetic experiments show that the dominant magnetic minerals in the samples are ferromagnetic magnetite and maghemite, which may contain a small amount of hematite, and its magnetic parameters at room temperature are comparable with those of loess in China. On the basis of the above results, we think that wind-formed loess deposits are widely distributed in the Indu-Ganges plain, and the existence of loess may promote the development of Indian farming, thus promoting the rise and prosperity of Indian ancient civilization. This provides a new and more mature carrier for the interpretation of paleoclimate information contained in strata in this area.
【作者单位】：福建师范大学地理研究所;湿润亚热带山地生态国家重点实验室培育基地;Department
【基金】：国家自然科学基金项目(批准号:41210002、U1405231和41602185)资助
【分类号】：S151

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