鄱阳湖地区末次冰期以来风成沉积体系研究

Aeolian deposits ( including aeolian sand and loess deposits ) are widely distributed in Poyang Lake region located in the middle reaches of the Yangtze River. The former, known locally as sand hills, is mainly distributed along the watercourses in the downwind direction of winter monsoon, and the latter, usually locate to the south of the sand hills, and show a systematical change ( from sand dune to sandy loess to silty loess to clayey loess ) away from the sand hills, reflect a winnowing of the coarse load away from the source. The winter monsoon intensified by funneling due to the "Y " shape of landform between the Yangtze river and its tributary the Ganjiang River, and the exposed fluvial-lacustrine flats was the main factors that combine to form the regionally aeolian deposital package. This aeolian deposital system is characterized by a single source area and stable prevailing wind. .Based on the distribution and thickness of loess, grain size, element geochemistry, mineral compositions, and their OSL dating, three transects ( including Furong-Zhouxi, a hilly transect, Houtian -Liangshan, a fluvial- lacustrine plain transect and Weijian-Jinhu, a mountainous transect ), all roughly paralleling the regional winter monsoon wind, would been investigated with mainly focusing on the Furong-Zhouxi one. This research would been conducted on the sorting and differentiation of grain size, grain form, element geochemistry, mineral compositions, and the spatial and temporal character of loess deposits, to develop standard modes of grain size and grain form and element geochemistry changes of entirely aeolian deposits systems away from the sources. This research might provide a reference for the future study of the China southern loess, clayey red earth and even vermicular red earth, and also serve the tracking research of elements for complex aeolian deposital systems in dry areas.

鄱阳湖地区，长江、赣江的冬季风下风方向上往往发育丘岗状的砂质地貌-砂山；同时，区域地层在红粘土和网纹红土之上，发育一套黄土堆积，俗称黄帽子。二者分别得到了广泛关注和深入研究。研究表明它们是风成沉积，均是冬季风从长江、赣江河谷搬运的碎屑颗粒在下风方向的颠扬堆积，空间上形成了从北到南的砂→砂黄土→黄土→粘黄土的区域风成沉积体系。本研究拟基于地层分布与厚度、粒度、元素地球化学、OSL年代，选择芙蓉-周溪（重点断面）、厚田-良山与新港-金湖三个与冬季风风向大致平行的断面，开展丘陵、河湖平原与山地等不同下垫面情况下，风成沉积地层时空变化、沉积粒度、粒形、元素地球化学的分选与分异研究，建立单物源，单风向环境下完整的风成沉积体系中粒度分选、粒形变化与地球化学元素分选、分异的标型模式。对这种区域风成沉积体系的研究，可为南方黄土、粘红土甚至是网纹红土的研究提供重要借鉴，也为干旱区复杂风成沉积研究提供参考。

在鄱阳湖地区，长江、赣江的冬季风下风方向上往往发育一系列丘岗状的砂质地貌-砂山；同时，区域地层在红粘土和网纹红土之上，发育一套黄土堆积（有学者认为与宁镇地区晚更新世下蜀黄土类似，称之为赣北下蜀黄土），土壤学上俗称“黄帽子”。二者分别得到了广泛关注和深入研究，但一直存在巨大争议。最近研究表明，它们均是风成沉积，均是冬季风从长江、赣江河谷漫滩地貌环境搬运的碎屑颗粒在下风方向的颠扬堆积，空间上形成了从北到南的砂→砂黄土→黄土甚至粘黄土的区域风成沉积体系。本研究基于地层分布特征与地层厚度、粒度、元素地球化学、AMS-14C和OSL 测年，选择芙蓉-周溪（重点断面）、厚田-良山与新港-金湖（次要断面）三个与冬季风风向大致平行的断面，开展了区域粉尘堆积体系中沉积地层时空变化、沉积粒度、元素地球化学的分选与分异研究，建立了单物源，单风向环境下完整的风成沉积体系中粒度与地球化学元素分选、分异的标型模式。这种基于粒度三组份（砂、粉砂、粘土）和稳定元素（例如AL2O3、TiO2、ZrO2或者元素对）三组份所建立的单物源、单风向的区域粉尘堆积的标型模型，为粉尘堆积体系的物源示踪提供了理论基础和方法思路。研究既可为南方黄土、粘红土甚至是网纹红土的研究提供重要的助力，也为干旱区复杂风成沉积研究提供了重要的借鉴。