渭河盆地河湖沉积碳酸盐及其碳氧同位素记录的上新世东亚季风气候变化  

EAST ASIAN MONSOON VARIATIONS DURING THE PLIOCENE REVEALED BY CARBONATE CONTENT,CARBON AND OXYGEN ISOTOPIC COMPOSITIONS OF THE FLUVIAL-LACUSTRINE SEDIMENTS IN THE WEIHE BASIN(CENTRAL CHINA)

作　　者：黄子晗 鹿化煜[1] 梁承弘 王可欣 张红艳[1] 王逸超 赖文 HUANG Zihan;LU Huayu;LIANG Chenghong;WANG Kexin;ZHANG Hongyan;WANG Yichao;LAI Wen(Jiangsu Collaborative Innovation Center for Climate Change,School of Geography and Ocean Science,Nanjing University,Nanjing 210023,Jiangsu)

机构地区：[1]南京大学地理与海洋科学学院,江苏省气候变化协同研究中心,江苏南京210023

出　　处：《第四纪研究》2022年第6期1475-1488,共14页Quaternary Sciences

基　　金：国家自然科学基金创新研究群体项目(批准号:42021001)和国家自然科学基金重点国际(地区)合作研究项目(批准号:41920104005)共同资助。

摘　　要：对上新世暖期(5~3Ma)大气CO_(2)高浓度背景下气候变化的研究,有助于理解当前大气CO_(2)浓度快速上升对气候变化的影响。文章对晚中新世-上新世(6.73~2.58Ma)渭河盆地268.5m厚的河湖相沉积序列的碳酸盐含量及其碳氧同位素组成进行分析,重建了这一时期的气候变化过程。结果表明,渭河盆地河湖相沉积序列中的碳酸盐主要是自生形成,受季风降水量变化控制,沉积物碳酸盐含量响应区域蒸发和降水比值。碳酸盐碳同位素组成可能主要反映湖泊初级生产力的强度,氧同位素组成变化反映降水量的变化。利用沉积物碳酸盐含量及其碳氧同位素组成重建渭河盆地晚中新世-上新世的干湿变化,表明约6.7Ma时期气候炎热干燥,6.7~4.5Ma时期整体较为温暖湿润,降水量在5.6~5.2Ma达到最大;约4.2Ma以后,气候向寒冷、干旱方向发展。本研究认为,晚中新世-上新世渭河盆地的季风降水可能由北半球温度变化驱动,表现出明显的阶段性变化特征。The study of climate change during the Pliocene warm period(5~3 Ma)under the high atmospheric CO_(2)concentration is helpful to understand the impact of the current rapid increase of atmospheric CO_(2)concentration on climate change. Weihe Basin is a fault basin which was formed in the northern margin of Qinling orogenic belt during Cenozoic period. It is located in the margin of East Asian monsoon circulation and semi-arid region of China, and it is a sensitive area in reponses to the monsoon variations. The Cenozoic sedimentary sequence in the Weihe Basin is of great significance to understand the climate and environment changes in Central China and East and Central Asia. Using Fourier Transform Infrared Spectroscopy(FTIR)and stable isotope mass spectrometer(MAT-253), carbonate content and carbon and oxygen isotopic composition of samples from a 268.5 m-thick fluvial and lacustrine sedimentary sequence(34.3051°N, 109.5021°E) in the Weihe Basin during the Late Miocene to Pliocene(6.73~2.58 Ma)were analyzed, in order to reconstruct the East Asian monsoon climate change during this period. The results show that the carbonate is mainly authigenic and mainly distributed in 6.7~4.5 Ma. The carbonate content ranges from 0 to 31%, which were controlled by variations of the monsoon precipitation and responded to the regional humidity. Correlation between carbon isotopic composition(δC)and oxygen isotopic composition(δO)of carbonate is low, and the carbonate strata may be deposited in an open freshwater lake environment. δCdistribution ranged from-4.20‰ to-13.96‰, and gradually decreases after reaching the maximum value at 6.7 Ma, δCmay mainly reflect the changes of lake primary productivity. δOranged from-6.82‰ to-12.42‰, and rapidly decreased to a low level(-9‰ to-11‰)after reaching the maximum value at 6.7 Ma, δOmainly reflects the change of precipitation. Based on the carbonate content and their carbon and oxygen isotopic composition, palaeoclimate variations in the Weihe Basin during the Late Mio

关 键 词：上新世 碳酸盐含量 碳氧同位素 渭河盆地 古气候重建 

分 类 号：P597.2[天文地球—地球化学] P593[天文地球—地质学] P534.622