何薇^1,2,3,,
汪亘^1,2,
王永莉^4,,,
魏志福^1,2,
巩俊成^1,2,
张婷^1,2,3,
马雪云^1,2,3,
玉晓丽^1,2,3
1. 中国科学院西北生态环境资源研究院, 甘肃 兰州 730000
2. 甘肃省油气资源研究重点实验室/中国科学院油气资源研究重点实验室, 甘肃 兰州 730000
3. 中国科学院大学, 北京 100049
4. 中国科学院地质与地球物理研究所, 中国科学院新生代地质与环境重点实验室, 北京 100029

基金项目: 国家重点研究发展计划项目（批准号：2017YFA0604803）、国家自然科学基金项目（批准号：41572350和41503049）、西部之光一般项目以及甘肃省油气资源研究重点实验室/中国科学院油气资源研究重点实验室开放课题（批准号：1309RTSA041）共同资助


详细信息

作者简介: 何薇, 女, 25岁, 硕士研究生, 有机地球化学专业, E-mail:hewei16@mails.ucas.edu.cn

通讯作者: 王永莉, E-mail:ylwang@mail.iggcas.ac.cn

中图分类号: P941.78;P593;P534.63⁺2;P532

收稿日期:2018-05-07
修回日期:2018-07-17
刊出日期:2018-09-30

Characteristics of climate and environment over the past 30ical.ka B.P. recorded in lacustrine deposits of the Qionghai Lake, Sichuan Province

He Wei^1,2,3,,
Wang Gen^1,2,
Wang Yongli^4,,,
Wei Zhifu^1,2,
Gong Juncheng^1,2,
Zhang Ting^1,2,3,
Ma Xueyun^1,2,3,
Yu Xiaoli^1,2,3
1. Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, Gansu
2. Key Laboratory of Petroleum Resources, Gansu Province/Key Laboratory of Petroleum Resources Research, Chinese Academy of Sciences, Lanzhou 730000, Gansu
3. University of Chinese Academy of Sciences, Beijing 100049
4. Laboratory of Cenozoic Geology and Environment, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029


More Information

Corresponding author: Wang Yongli,E-mail:ylwang@mail.iggcas.ac.cn

MSC: P941.78;P593;P534.63⁺2;P532

--> Received Date: 07 May 2018
Revised Date: 17 July 2018
Publish Date: 30 September 2018


摘要
摘要:以我国西南地区邛海钻孔沉积物为研究对象，利用高分辨率粒度数据，结合正构烷烃指标特征，探讨了研究区30 cal.ka B.P.以来的植被演化和气候环境变化过程。研究表明，邛海沉积有机质主要来自于外源的高等陆生植物和内源的水生生物（低等菌藻类生物和挺水、沉水和漂浮植物）。沉积物粒度组成及正构烷烃代用指标变化特征表明，邛海地区过去30 cal.ka B.P.以来的气候环境变化过程大致分为4个阶段：1）29.1~23.0 cal.ka B.P.，沉积物中值粒径（Md）均值为22.4 μm，正构烷烃平均碳链长度（ACL值）和陆生植物正构烷烃相对输入量指标（P_wax值）呈高值，指示相对暖湿的气候条件，湖区以草本植物为主；2）23.0~19.0 cal.ka B.P.，沉积物中值粒径明显减小，均值为15.4 μm，同时ACL值、P_wax值为低值，指示温度较低，气候干燥，这一时期植被类型以木本植物为主；3）19.0~11.0 cal.ka B.P.，中值粒径减小，均值为10.4 μm，ACL值总体较低，P_wax值由高转低，研究区气候从由暖湿向冷干转变，木本植物扩张；4）自11.0 cal.ka B.P.以来沉积颗粒表现出"细-粗-细"的变化特点，中值粒径均值为11.5 μm，ACL值、P_wax值由低值先升高后降低，揭示这一时期邛海气候"冷干-暖湿-冷干"的变化过程，湖区经历了草本植物先扩张后收缩的过程。特别的是，邛海沉积物记录的23.0~19.0 cal.ka B.P.、12.8~11.7 cal.ka B.P.和9.0~5.0 cal.ka B.P.这3次典型气候时期，在时间和气候特征上与末次冰盛期（LGM）、新仙女木事件（YD）和全新世气候适宜期（HCO）相符，可能是对西南季风强度变化及地质历史时期典型气候事件的响应。
关键词: 湖泊沉积物/
粒度特征/
正构烷烃/
古气候环境/
邛海

Abstract:Qionghai Lake is located in the transition zone of southeast Tibetan Plateau and southwest of Sichuan Province, SW China. In order to reconstruct the paleoclimate and paleoenvironment of Qionghai Lake area, a continuous 23.9-m long sediment core(27°50'42.92"N, 102°20'9.25"E) was obtained in 2013 in the northeast of Qionghai Lake. The lithology is mainly lacustrine brown-yellow and grey silt. The chronology was established based on the AMS ¹⁴C data of twelve plant remains, extending back to about 29.1 cal. ka B.P. A total of 72 samples were taken at a 30-cm interval for n-alkanes analysis and 186 samples were collected at a 10-cm interval for grain-size analysis.
The bimodal distribution of n-alkanes from Qionghai Lake sediments indicate that the organic matters were derived from both exogenous higher land plants and endogenous aquatic plants(including aquatic algae, and emergent, submerged and floating macrophytes). Based on the geographical location of Qionghai Lake and its characteristics, the paleoclimate significances of grain-size of Qionghai Lake sediments were discussed. In general, variations of grain-size data of Qionghai Lake sediments could effectively indicate paleo-precipitation history in the study area. When the southwest summer monsoon was strong, the coarse particles were easy to deposit in the study area due to the heavy precipitation and strong hydrodynamics, indicating a humid climate condition. Whereas, the increase of fine fraction of Qionghai Lake sediments may correspond to a relatively dry climate. Besides, P_aq(aquatic plant n-alkane proxy) and P_wax(land plant n-alkane proxy) were also applied to infer the climate conditions. Generally, high P_aq and low P_wax values reflect a low input of terrestrial plants, and thus a weak surface runoff under a relatively dry climate. According to the grain size characteristics and n-alkane-based proxies, the paleoclimate conditions in Qionghai Lake area can be divided into four stages somewhat arbitrarily:Stage Ⅰ(29.1~23.0 cal.ka B.P.), the median particle diameter(Md) of Qionghai Lake sediments were 22.4 μm, reaching the highest value in the entire profile, and the values of ACL(average chain length of n-alkanes) and P_wax were high, indicating a relatively warm and moist climate. And the vegetation types were maily grasses. Stage Ⅱ(23.0~19.0 cal.ka B.P.), the Md value decreased to 15.4 μm, with low values of ACL and P_wax, suggesting a cold and dry climatic condition. And the vegetation was dominated by woody plants during this stage. Stage Ⅲ(19.0~11.0 cal.ka B.P.), the Md value of sediments decreased to 10.4 μm. Additionally the values of ACL were low and P_wax decreased, indicating climate changed from warm-moist to cold-dry condition. And the woody plants expanded during this period. Stage Ⅳ(11.0 cal.ka B.P. to present), the median grain size were 11.5 μm. However, the sediment particles exhibited "fine-coarse-fine" periodical fluctuations, and values of ACL and P_wax increased and then decreased, reflecting the cold and dry climate changed to warm and humid condition, and then shifted to cold and dry climate again. Meanwhile, the grasses in Qionghai Lake area expanded in the Early to Middle Holocene and then shrinked in the Late Holocene. It is worthy to note that the specific climate conditions in Qionghai Lake area in the interval of 23.0~19.0 cal.ka B.P., 12.8~11.7 cal.ka B.P. and 9.0~5.0 cal.ka B.P., were coincident with the Last Glacial Maximum(LGM), Younger Dryas(YD) event, and Holocene Climatic Optimum(HCO), respectively, probably in response to the varying intensities of southwest summer monsoon and typical climatic events.
Key words:lacustrinesediments/
grain-size characteristics/
n-alkanes/
paleoclimate and paleoenvironment/
Qionghai Lake



PDF全文下载地址:

http://www.dsjyj.com.cn/data/article/export-pdf?id=dsjyj_11532