Holocene environmental evolution recorded by multi-proxies from lacustrine sediments of the Hangbu River Valley, Lake Chaohu Basin, East China

Abstract

在巢湖杭埠河流域中的古湖盆中心——三河圩区获取28.6 m长的湖相岩芯（SZK1507孔），利用AMS¹⁴C测年技术建立可靠的地层年代序列，通过对SZK1507孔738 cm以上段湖相沉积物平均粒径、磁化率、总氮（TN）、总有机碳（TOC）及C/N的综合分析，高分辨率重建了巢湖杭埠河流域全新世以来的古环境演变过程.结果表明，本区域的环境变化过程可以分为4个阶段，阶段Ⅰ（约10050—9700 cal.a B.P.）与阶段Ⅲ（约9250—5300 cal.a B.P.）气候较为湿润，巢湖水位较高，平均粒径、磁化率值较低，TN、TOC、C/N也偏低；阶段Ⅱ（约9700—9250 cal.a B.P.）与阶段Ⅳ（约5300 cal.a B.P.以来）气候干燥，巢湖水量减少，水位降低，平均粒径、磁化率值、TN、TOC、C/N均较高.一些全球范围内显著发生的气候突变事件在SZK1507孔沉积记录中也有体现，如9.3、8.2和4.2 ka B.P.事件等.将巢湖杭埠河流域10000 cal.a B.P.以来的平均粒径、磁化率、TN、TOC、C/N沉积记录与全新世以来的北纬30°夏季太阳辐射量、太阳黑子数、火山喷发对大气中硫酸盐含量贡献率等进行对比，发现巢湖杭埠河流域全新世气候突变事件主要受控于北半球夏季太阳辐射量变化、太阳活动以及火山活动等因素，并与它们之间复杂的响应机制有关.;Time sequence of the SZK1507 core derived from AMS¹⁴C dating, and the content of the total nitrogen (TN), total organic carbon (TOC) and the C/N values as well as the mean grain size, magnetisability are utilized to reconstruct the environmental changes in the Hangbu River Valley of the Lake Chaohu Basin, East China during the Holocene. The comprehensive analyses of multiple alternative proxies indicated that the evolutionary process of Lake Chaohu Basin in the Holocene could be divided into four periods. The climate was moist in Period Ⅰ ( from 10050 cal. a B.P. to 9700 cal. a B.P.) and Period Ⅲ (from 9250 cal. a B.P. to 5300 cal. a B.P.), and lake level of Lake Chaohu was high inferred from the low values of TN, TOC, C/N, mean grain size and magnetisability. Period Ⅱ (from 9700 cal. a B.P. to 9250 cal. a B.P.) and Period Ⅳ (from 5300 cal. a B.P. to the present) were dry, and the Lake Chaohu had low lake level, suggested by the high values of mean grain size and magnetisability, TN, TOC, C/N. Some global-scale abrupt climatic change events (e.g., 9.3 ka B.P., 8.2 ka B.P., and 4.2 ka B.P. events) were also recorded in this sediment core. Comparing the lacustrine records of SZK1507 core to other observations of climate variability, such as the northern hemisphere summer solar insolation, the sunspot numbers etc during the Holocene, we discovered that the abrupt climatic change events occurring in the Lake Chaohu Basin were affected by the variation of summer solar insolation in the northern hemisphere, the solar activities, the volcanic activities, and the complex feedback mechanism among them principally.