摘要
神农架大九湖沼泽泥炭柱状样提供了分辨率为25a的约2600a来的气候变化记录。对样品进行了环境磁学参数测量、X射线荧光分析(XRF)、孢粉鉴定和统计建模,结果表明,大九湖气温的变化曲线与竺可桢中国东部的物候温度曲线以及格陵兰氧同位素变化曲线大体一致,与青藏高原东部希门错湖泊沉积物温度代用指标的变化曲线也十分相似。特别是550—1300AD间的相对温暖期,与竺可桢首次提出来的中国东部隋唐温暖期(约600—1000AD)和欧洲的中世纪暖期(930—1240AD)在时间跨度上大致对应。可划分为4个阶段:(1)600BC—550AD,气候相对冷湿;(2)550—1300AD,气候相对凉干;(3)1300—1900AD,气候又转变为冷湿,其中最冷期1400—1900AD可与欧洲的小冰期对应;(4)1900AD至今,气候又开始转向相对凉干。同时发现低频磁化率χlf与铁元素含量之比(χlf/Fe)的变化曲线与利用孢粉分析数据恢复的大九湖气候变化曲线对应得很好,特别是二者都清晰地显示了500—1300AD为一相对暖期。这预示着χlf/Fe可能是泥炭剖面的一个更好的气候记录代用指标。
Peat column from the Dajiu Lake basin provides 25aresolution records showing climatic changes since the last 2 600 years. By means of multiple regression analyses, a model for pollenclimate is established and a highresolution record of the climate and environment is constructed. The record is compared with the results from magnetism and XRF measurement and with the environmental change records from other areas in the same period. From these, we know that climate change of the Daqiu Lake basin since the last 2 600 years run roughly consistent with the ZHU Kezhen's temperature curve and the Greenland isotopic curve, and also with the curve of substitute indices for the lacustrine sediments in the east of the QinghaiTibet Plateau. Attention should be specially paid to the relatively warm period of 550—1300AD, whose time span is nearly the same as the SuiTang Dynasty warm period (600—1000AD) in the east of China first proposed by ZHU Kezhen and as the medieval warm period in Europe (930—1240AD). The whole climatic record can be divided into four periods: ①relatively coldwet period of 600BC—550AD; ②relatively cooldry period of 550—1300AD; ③coldwet period of 1300—1900AD, with the coldest time (1400—1900AD) corresponding to the 'Little Ice Age'; ④climate turning to relatively cooldry again (from 1900AD to present). The peat core (DJH3) has quite low values of magnetism parameters such as χlf, SIRM and χARM, indicating that concentrations of magnetic minerals in the peat are low due to the dilution of humus and other organic materials. In the core, the χfd% values of all samples are near zero, and the values of S300mT% and S100mT% for most of the samples are near 100 percent, implying that magnetism of the peat core is dominated by fine ferromagnetic minerals. There is a good correspondence between the fluctuating curve of χlf/Fe (the ratio of susceptibility and Fe content) in the DJH3 core and that o
出处
《海洋地质与第四纪地质》
CAS
CSCD
北大核心
2003年第2期109-115,共7页
Marine Geology & Quaternary Geology
基金
国家自然科学基金资助项目(40271119)
中国地质大学湖北省地层表层系统实验室测试基金项目
