王婷^1,2,,
龙宜澧^1,2,
刘星星^1,3,
孙有斌^1,3,4,,
1. 中国科学院地球环境研究所, 黄土与第四纪地质国家重点实验室, 陕西 西安 710061
2. 中国科学院大学, 北京 100049
3. 中国科学院第四纪科学与全球变化卓越创新中心, 陕西 西安 710061
4. 西安交通大学全球变化研究院, 陕西 西安 710054

基金项目: 国家自然科学基金****项目（批准号：41525008）、国家自然科学基金项目（批准号：41807425）、中国科学院地球环境研究所黄土与第四纪地质国家重点实验室开放基金项目（批准号：SKLLQG1831和SKLLQG1633）共同资助


详细信息

作者简介: 王婷, 女, 25岁, 博士研究生, 第四纪地质学, E-mail:wangting@ieecas.cn

通讯作者: 孙有斌, E-mail:sunyb@ieecas.cn

中图分类号: P534.63;P594;P532

收稿日期:2019-01-30
修回日期:2019-03-15
刊出日期:2019-05-30

Sedimentary environment evolutions in the Weihe Basin since Last Glacial Maximum

Wang Ting^1,2,,
Long Yili^1,2,
Liu Xingxing^1,3,
Sun Youbin^1,3,4,,
1. State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an 710061, Shaanxi
2. University of Chinese Academy of Sciences, Beijing 100049
3. Center for Excellence in Quaternary Science and Global Change, Chinese Academy of Sciences, Xi'an, 710061, Shaanxi
4. Institute of Global Environmental Change, Xi'an Jiaotong University, Xi'an 710054, Shaanxi


More Information

Corresponding author: Sun Youbin,E-mail:sunyb@ieecas.cn

MSC: P534.63;P594;P532

--> Received Date: 30 January 2019
Revised Date: 15 March 2019
Publish Date: 30 May 2019


摘要
摘要:研究过去气候快速变化能为当前极端气候分析和未来环境预测提供自然背景理解。亚洲季风在北半球乃至全球的第四纪气候变化中扮演着重要角色，其演化是全球气候变化背景下的典型区域响应。然而，不同地质载体及不同指标所记录的亚洲冬、夏季风变化存在着较大差异，产生差异的原因及受到的动力机制是值得深入研究的科学问题。渭河盆地位于黄土高原和古三门湖沉积交叠的区域，是研究第四纪亚洲季风演化的理想场所。在盆地西南部西安市户县和长安县获取了两个黄土沉积钻孔，户县ZZC孔长4 m，长安县XFC孔长3 m，两孔的年代均超过25 ka。通过两钻孔的粒度和元素地球化学等代用指标研究，对比分析不同指标对气候变化的敏感度差异，反演了末次冰盛期（LGM）以来的区域沉积环境变化，并尝试探讨该时期发生的气候突变事件及反映的季风强度变化。结果表明，两钻孔的平均粒径从LGM到中全新世逐渐变细，中全新世之后少许变粗，空间上表现出一致性，总体反映了末次冰盛期以来的冬季风强度演化；Ca/Ti反映了与季风降水相关的淋溶强度，从LGM到全新世暖期夏季风逐渐减弱，并记录了若干次气候快速变化。粒度和元素比值变化表明，渭河盆地沉积良好地记录了末次冰盛期至全新世的大幅冷干-暖湿波动及若干次持续时间较短的快速水文变化事件，主要是受到太阳辐射和冰量等因素调控的影响。由于渭河盆地有上千米的新生代沉积，未来开展高分辨率研究有望揭示不同时间尺度季风变化特征及其与区域和全球变化的联系。
关键词: 渭河盆地/
末次冰盛期(LGM)/
粒度/
元素地球化学/
冬/夏季风演化

Abstract:Studies of rapid climate changes provide a scientific understanding for humans facing with extreme climate and predicting future environments dynamics. Asian monsoon, as a key interactive transmitter of high-and low-latitude climate, has played a significant role in Northern Hemisphere and global Quaternary climate changes. There are, however, remarkable differences and distinctions recorded in varied paleoclimatic proxies and researches of rapid monsoon changes at millennial timescales remain poorly constrained, therefore, further discussions are necessary about Asian monsoon variations.
Weihe Basin is located at the overlapping area of Chinese Loess Plateau(CLP) and Sanmen Lake sediments, which is an excellent area of studying the evolution of Quaternary Asian monsoon variability. We conduct a comparative study of grain size(2-cm resolution) and elemental concentrations(scanning by 2-cm resolution) of two high-quality loess cores, named ZZC(34°8'20"N, 108°42'26"E) and XFC(34°8'11"N, 108°45'23"E) in Weihe Basin, evaluate the relations of different spatial and climate proxies, and try to reconstruct East Asia monsoon(EAM) evolution since Last Glacial Maximum(LGM). The upper 4-m of ZZC core and 3-m of XFC core are homogeneous in lithology, brown-yellow alternate between in colors. The construction of timing of two cores are based on tuning with adjacent Weinan aeolian loess which knowns OSL ages, three age control points(about 24 ka, 15 ka and 4 ka, respectively) are selected to match the boundaries of LGM and Holocene. Based on above analysis, the results show that mean grain size(MGS) of two cores exhibit synchronous fluctuations and match well with Weinan aeolian loess, while Ca/Ti shows relatively higher amplitude and frequency than MGS. Generally, grain size can be an indicator of East Asia winter monsoon(EAWM) and Ca/Ti can be an indicator of East Asia summer monsoon(EASM). MGS of ZZC core decreases from LGM to Early Holocene, and become slightly coarser after mid-Holocene, which means East Asia winter monsoon(EAWM) is strong since LGM to Early Holocene and Late Holocene, but weak during the mid-Holocene. Ca/Ti decreases from LGM to the Holocene, indicating EASM intensity changes greatly during this periods, moreover, several abrupt monsoon events is recorded in Ca/Ti at LGM and last deglaciation. During the Holocene(especially mid-Holocene), Ca is almost completely leached due to excessive precipitation and the sensitivity of Ca/Ti is fade away. Both EASM and EAWM are comprehensive modulated by Northern hemisphere summer insolation(NHSI) and cooling effect of Laurentide ice since LGM.
Our study shows that climate of the Weihe Basin changed from dry/cold of LGM to warm/humid of Holocene. In the further investigation about Weihe Basin and EAM, more data assimilation should be focused on the high-resolution and univocal EAM proxies and studies of hydrological cycle changes. Moreover, robust evaluation of the regional response to global climate changes and further projection of East Asian monsoon variability are crucial to the characteristics and mechanisms of monsoon climate.
Key words:Weihe Basin/
Last Glacial Maximum(LGM)/
grain size/
elemental geochemistry/
winter/summer monsoon evolution



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