摘要
碳酸盐矿物是黄土的重要组成部分,是古环境重建的重要指标之一。通过对地处西风区的新疆伊犁盆地昭苏黄土剖面的全岩样品和分粒级样品的X射线衍射测试,分析了其碳酸盐矿物组成,利用麦夸特算法计算了碳酸盐矿物的含量。综合碳酸盐矿物的含量、粒径分布及风化特征等因素,对其古环境意义进行了辨识,从而建立了该剖面末次冰期以来碳酸盐矿物记录的古气候环境变化序列。结果表明:昭苏剖面中原生碳酸盐矿物(方解石和白云石)含量占主导地位,次生方解石对样品中总方解石含量的贡献较少;白云石含量可能与亚轨道尺度冷暖交替导致的西风环流强度变化有关;方解石含量的变化可能指示了西风区降水量的变化;碳酸盐矿物含量揭示了昭苏地区在末次冰期时气候冷湿,在全新世时气候暖干。
The carbonate minerals are important components of loess sediments, and they are regarded as the effective proxy indexes for paleoclimate reconstruction in the Chinese Loess Plateau. The loess-paleosol sequence in the Ili Basin dominated by westerly circulation provide a good archive for the research of the history of paleoenvironment and paleoclimate and westerly circulation. However, paleoclimatic significance and adaptability of carbonate minerals of eolian loess sediments in the Ili baisn are still unknown. Here,the authors report carbonate minerals results of a 690cm thickness loess-paleosol sequence （ named Zhaosu Poma （ZSP） section）. The ZSP loess section （42.69°N, 80.25 °E ; elevation 1875m） is situated on a second terrace of the Tekes river in the South Ili Basin. The section can be divided into five pedostratigraphic units with bottom of the upper S1 overlying on fluvial gravel sediments. According to the extrapolation of OSL dating, the age of the bottom of this section is nearly 80ka. Based on X-ray diffraction analysis ,the authors report the carbonate minerals composition both in 138 bulk samples and 45 different grain size fractions of ZSP. Levenberg-Marquardt（LM） method is applied to determine the quantitative analysis of carbonate minerals. Besides,the paleoenvironmental significances of calcite and dolomite are discussed according to their content, grain size distribution and weathering characteristics. Then climatic changes since the last glacial period have been constructed in term of carbonate minerals. The results show that the carbonate minerals are dominated by detrital carbonate such as calcite and dolomite. Pedogenic carbonate （mainly calcite ）has little contribution to total carbonate. The content of dolomite is related with westerly circulation intensity variations caused by alternation of sub-orbit scale cold and warm climate. The content variations of calcite maybe reflect the precipitation changes in westerly area. Therefore, the contents of carbonate minerals
出处
《第四纪研究》
CAS
CSCD
北大核心
2013年第3期424-436,共13页
Quaternary Sciences
基金
国家自然科学基金项目(批准号:41172166和40972230)
国家重点基础研究发展规划项目(973项目)(批准号:2010CB833406)共同资助
关键词
碳酸盐矿物
西风环流
降水
温度
X射线衍射
carbonate minerals
westerly circulation
precipitation
temperature
X-Ray diffraction
