干旱区生态环境知识资源中心(Arid): 天山北麓地区博乐黄土磁化率、粒度特征与古气候意义

Arid

	天山北麓地区博乐黄土磁化率、粒度特征与古气候意义
其他题名	Magnetic susceptibility and grain size records of Bole loess section in the northern piedmont of Tianshan Mountains and their implications for paleoclimatic changes
	孙焕宇 1; 宋友桂 2; 李越 3; 陈秀玲 1
来源期刊	地球环境学报
ISSN	1674-9901
出版年	2018
卷号	9 期号:2 页码:123-136
中文摘要	受西风控制的天山地区黄土广泛分布,是中亚重要的黄土分布区之一。这些陆相风成沉积物为研究中亚干旱区气候环境变化历史提供了重要的信息载体。本文选取天山北麓博乐地区一个厚为12.7 m的黄土剖面作为研究对象,分析了其磁化率、粒度指标的变化特征,并探讨了其古气候意义。结果表明: (1)博乐黄土粒度组成以粉砂为主,是典型的风成沉积物,成壤作用很弱;(2)博乐黄土磁化率变化主要受控于风力强度;(3)剖面粒度的环境敏感粒级为<31.7 mum、31.7 282.5 mum,分别可能代表风暴过后的浮尘堆积和风暴过程中风力近距离搬运的沉积物组分;(4)博乐黄土MIS(海洋氧同位素)3阶段记录了多次千年尺度气候事件,能与北大西洋Heinrich事件和D-O事件对应,表明中纬度西风环流在传递北大西洋信号到东亚的过程中扮演着重要角色。
英文摘要	Background, aim, and scope Loess-paleosol sequences provide key aeolian archives for Quaternary climate changes. Loess as an aeolian sediment are closely related to climate changes during mobilization, transportation and deposition process. Grain size (GS) and magnetic susceptibility (MS) of loess sediments are regarded as important paleoclimatic proxies in the Chinese Loess Plateau. Loess sediments are also extensively distributed in westerly-dominated Tianshan Mountains area. However, their paleoclimate proxies are not fully understood by now. In this paper, we selected a loess section from north piedmont of Tianshan Mountains to investigate the paleoclimatic significances of these proxies. This section provides an important archive for climatic and environmental change history in the arid Central Asia. Materials and methods Bole loess section has a thickness of 12.7 m. A total of 635 samples were collected at 2 cm intervals for GS and MS analyses. GS distribution was analyzed using a Malvern 2000 laser instrument, and calculated for 100 grain size classes within a measuring range of 0.02 2000 mum. MS was measured with a Bartington MS2 meter both low- (0.47 kHz) and high- (4.7 kHz) frequency magnetic susceptibility (chilf and chihf, respectively). All measurements were completed at the State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences. Seventeen age samples were measured in the Xi’an AMS facility, and all radiocarbon dates were calibrated to calendar years. The visual curve matching method is used to establish age-depth model of this section, due to deficiencies and shortcomings of 14C age. The grain size-standard deviation method here has been employed to extract the environmental sensitive components. Results The results show that (1) Variations in chilf range from 38.8010~(-8) m~3 · kg~(-1) to 84.7010~(-8) m~3 · kg~(-1) with an average of 59.52*10~(-8) m~3·kg~(-1). Frequency-dependent magnetic susceptibility (chifd) and frequency-dependent magnetic susceptibility (chifd%) yield consistently low values throughout the BL section; (2) The BL loess is dominated by fine silt-sized particles (21.69% 69.65%, with an average of 44.58%). Coarse silt-sized particles vary from 17.95% to 40.60%, averaging 31.68%. Sand fraction component account for 6.78% 40.50%, averaging of 17.33%. BL loess contains minor clay-sized particles (1.66% 14.69%, 6.41%); (3) The 14C ages almost stop increasing by ca. 25 cal ka BP at ~1 m depth). (4) Two sensitive components (<31.7 mum and 31.7 282.5 mum) were distinguished. Discussion Variations in chifd and chifd% throughout the BL section suggest weak pedogenesis, and MS is more strongly influenced by allogenetic magnetic minerals than pedogenesis. Therefore, wind strength may control on the MS enhancement of this section. The BL loess GS is dominated by silt-sized particles, suggesting a typical aeolian sediment. Two sensitive components represent suspension after dust storm and proximal deposit component mainly transported by dust storms, respectively. We compare the 31.7 282.5 mum sensitive component to delta~(18)O records from Greenland ice core and the July solar insolation at 65°N based the age-depth model, variations in grain size of this section indicate good correlations to the global climate change especially millennial scale climate events during MIS3. Conclusions The BL loess is a typical aeolian sediment, which experiences very weak pedogenesis. MS variabilities are controlled by wind strength, and wind vigor model can apply to explain the MS enhancement of the BL loess.
中文关键词	黄土 ; 磁化率 ; 粒度 ; 敏感组分 ; 气候事件 ; 天山
英文关键词	loess magnetic susceptibility grain size sensitive components climate events Tianshan Mountains
语种	中文
国家	中国
收录类别	CSCD
WOS类目	GEOLOGY
WOS研究方向	Geology
CSCD记录号	CSCD:6242295
资源类型	期刊论文
条目标识符	http://119.78.100.177/qdio/handle/2XILL650/237434
作者单位	1.福建师范大学地理科学学院, 福建省湿润亚热带山地生态省部共建国家重点实验室培育基地, 福州, 福建 350007, 中国; 2.中国科学院地球环境研究所;;中国科学院中亚生态与环境研究中心, 黄土与第四纪地质国家重点实验室;;, 西安;;乌鲁木齐, ;; 710061;;830011; 3.中国科学院地球环境研究所;;中国科学院大学地球科学学院, 黄土与第四纪地质国家重点实验室;;, 西安;;, ;;北京 710061;;100049
推荐引用方式 GB/T 7714	孙焕宇,宋友桂,李越,等. 天山北麓地区博乐黄土磁化率、粒度特征与古气候意义[J],2018,9(2):123-136.
APA	孙焕宇,宋友桂,李越,&陈秀玲.(2018).天山北麓地区博乐黄土磁化率、粒度特征与古气候意义.地球环境学报,9(2),123-136.
MLA	孙焕宇,et al."天山北麓地区博乐黄土磁化率、粒度特征与古气候意义".地球环境学报 9.2(2018):123-136.