洞庭盆地黑褐色土壤地层成因、物源与古环境记录及其对人类活动的影响

The middle reaches region of Changjiang River is one of the core areas, which are the origins of civilization and agriculture in China. We select Dongting Basin, one of the core areas of the middle reaches region of Changjiang River, as a research area for this study. Base on scientific point of the man-land relationship evolution and through investigating and researching regional particular dark-brown soil strata in the tableland and hilly area, we deeply research sedimentary record of environmental change process and its impact on human activities in Dongting Basin area in China. In order to realize the target, we focus on several academic issues: (1) Genesis and material sources of the dark-brown soil, we study this scientific problem through the detrital minerals, rare earth elements, TOC and C/N analysis, as well as comparison with typical eolian sediments including loess in Loess Plateau, Xiashu loess from lower reaches of Changjiang River, reticulated red soil and homogenesis red soil from middle reaches of Changjiang River, fluvial sediments including Xiangjiang, Zishui, yuanshui, Lishui and Changjiang River sediments and ancient lacustrine sediments from the core in Dongting basin area. (2) Sediment precise dating, we determine the sediment precise years though using AMS14C and OSL dating methods. (3) Paleoclimatic and paleoenvironmental evolution, we reconstruct paleoclimatic and paleoenvironmental evolution by applying environmental proxies such as particle-size, magnetic susceptibility, geochemical elements, pollen and phytolith, TOC and C/N of sediments from dark-brown soil natural profiles. (4) Environmental background of ancient human activities, we study this issue by analyzing relics of archaeological sites profiles, pollen and phytolith of sediments from cultural strata, and comparing with strata of natural profiles. Thus, we can systematically study high-resolution environmental evolution in late Pleistocene / Holocene transition period and discuss environmental background of ancient human activities in Dongting Basin. These research achievements are of great theoretical significance to master laws of man-land relationship evolution in Changjiang River area, China.

长江中游地区是我国文明起源和农业起源的核心地区之一。本项目选取长江中游的核心区域之一- - 洞庭盆地为研究对象，通过对区域内台地/岗地黑褐色土壤地层这一特殊地层的调查研究，从人地关系演变科学角度，深入研究盆地区域沉积记录的环境变化过程及其对人类活动的影响，重点围绕黑褐色土壤的成因与物质来源（通过碎屑矿物、稀土元素、TOC 和C/N分析，并与典型风成沉积物、河流和古湖泊沉积物进行理化性质比较）、黑褐色土层的精确定年（AMS14C和OSL）、古气候与古环境演变（自然剖面的粒度、磁化率、地球化学、孢粉和植硅体、TOC 和C/N分析）、古人类活动的环境背景分析（遗址剖面的遗物分析、孢粉和植硅体，与自然剖面地层对比）开展研究，系统深入的研究盆地晚更新世/全新世过渡期高分辨率沉积记录的环境演变过程，全面探讨区域过渡期古人类活动的环境背景。这对于全面掌握我国长江流域人地关系演变规律，具有十分重要的理论意义。

长江中游地区是我国文明起源和农业起源的核心地区之一，是研究环境演变与人类活动互动关系的理想区域。本项目以长江中游的洞庭盆地为研究对象，通过对洞庭盆地原有资料的收集和整理研究、大量的野外考察、剖面描述和多个剖面（YC自然剖面、YBD遗址剖面、YZG遗址剖面、SZP遗址剖面、SLG自然剖面和SJG遗址剖面）和1个钻孔岩芯（华容钻孔）的系统取样和室内多种环境代用指标的分析，并结合AMS14C年代和释光年代（OSL），全面深入研究了洞庭盆地晚更新世晚期以来不同时期的环境演变及其对人类活动的可能影响。主要研究成果如下：（1）对研究区已有相关资料进行了详尽的收集、整理和分析研究，结合地形图和地质图进行室内分析和研究，并进行大量的野外考察，厘清楚了洞庭盆地的地质地貌特征和地层分布特征。（2）对洞庭盆地进行黑褐色土壤剖面的系统调查研究，对多个黑褐色土壤剖面如岩板垱（YBD）、玉成（YC）剖面等多个剖面的AMS14C和释光（OSL)年代学分析结果表明，黑褐色土形成年代为23ka BP-11ka BP，相当于深海氧同位素2阶段（MIS2阶段）。下部的黄土层相当于氧同位素3阶段（MIS3阶段）。（3）选取YC黑褐色土壤剖面进行沉积学、年代学和地球化学分析，并与黄土高原黄土、镇江下蜀黄土、洞庭盆地风成红土等典型风成沉积物和河流沉积物、湖泊沉积物和基岩风化红土等非风成沉积物进行比较研究，证明了黑褐色土壤沉积物的成因和可能的物质来源。（4）通过对洞庭盆地6个剖面和1个钻孔岩芯（华容钻孔）的密集采样和多种环境代用指标的分析（沉积物样品的粒度、磁化率、孢粉、有机碳和碳屑、常量元素、微量和稀土元素地球化学等的分析），以及AMS14C年代和释光年代（OSL）样品的测定，重建了洞庭盆地晚第四纪以来不同时间尺度的环境系统的演变过程与演化规律，恢复了不同时间尺度的人类活动信息。（5）全面进行了环境系统特征及变化规律信息与古人类活动的特征及规律信息进行全面的对比分析和研究，深入分析和探讨了洞庭盆地环境演变对人类活动的可能影响。