鹿化煜,
南京大学地理与海洋科学学院, 江苏 南京 210023
基金项目: 国家自然科学基金项目（批准号：41690111）和国家重点研究发展计划项目（批准号：2016YFA0600503和2016YFE0109500）共同资助
详细信息
作者简介: 汪苗, 女, 25岁, 硕士研究生, 自然地理学与环境演变专业, E-mail:1031639885@qq.com
通讯作者: 鹿化煜, E-mail:huayulu@nju.edu.cn
中图分类号: P597, P532收稿日期:2019-02-17
修回日期:2019-05-23
刊出日期:2019-09-30
Age, geochemical composition and their paleoclimatic implications of the basalt in Leizhou Peninsula, Southern China
Wang Miao,Lu Huayu,
School of Geography and Ocean Science, Nanjing University, Nanjing 210023, Jiangsu
More Information
Corresponding author: Lu Huayu,E-mail:huayulu@nju.edu.cn
MSC: P597, P532--> Received Date: 17 February 2019
Revised Date: 23 May 2019
Publish Date: 30 September 2019
摘要
摘要:我国南部雷州半岛是亚洲季风影响的核心区，区域内田洋、青桐洋和九斗洋这3个干玛珥湖沉积序列可为揭示低纬地区亚洲季风的轨道尺度变化提供关键证据。查明这些玛珥湖的形成年代、基底玄武岩的地球化学组成及其风化产物特征，为进一步获得沉积序列的年代控制、揭示沉积物替代指标的古气候意义提供了基础。本研究对3个干玛珥湖基底的玄武岩进行了K-Ar测年、地球化学成分和玛珥湖周围风化剖面粘土矿物的测试分析，得出了以下结论：1）田洋玛珥湖湖盆的形成年代为0.73~0.87 Ma，首次报道的青桐洋和九斗洋湖盆的形成时代分别为0.82 Ma和0.81~1.08 Ma，它们均属于早更新世晚期到中更新世早期的石峁岭期火山射气喷发形成的。2）田洋、青桐洋和九斗洋玛珥湖基底玄武岩均属于石英拉斑玄武岩。同一时期喷发的石英拉斑玄武岩广泛分布在玛珥湖的周围，这些玄武岩风化的产物以高岭石、三水铝石以及赤铁矿为主，在降水较为充沛的时期，物理或化学风化的产物随地表径流汇入湖盆，是玛珥湖沉积的主要来源。本研究为正在进行的低纬地区更新世轨道尺度季风降水重建提供了基础。
关键词: 雷州半岛/
玛珥湖/
玄武岩/
K-Ar测年/
风化作用
Abstract:Leizhou Peninsula in Southern China is a core region which is affected by the Asian monsoon circulation. The sedimentary sequences of three dry maar lakes in this region, namely Tianyang Lake (20°31'10.08"N, 110°18'02.66"E), Qingtongyang Lake (20°34'07.59"N, 110°09'48.1"E) and Jiudouyang Lake (20°38'08.78"N, 110°02'05.13"E) can provide pivotal evidence for revealing the orbital scale variations of Asian monsoon in low-latitude regions. In order to obtain the chronology control of sedimentary sequence and reveal paleoclimate implication of the sediment proxy indexes, it is fundamental to clarify the age and geochemical composition of basalts at the base of these dry maar lakes, and to understand the possible impact of their weathering products to the lake deposits. In this study, we carried out K-Ar dating and geochemical analysis on these basalts, and measured the clay minerals of the weathering soil profiles surrounding these maar lakes. On the basis of our analyses, the following conclusions are drawn:(1) K-Ar dating results show that the Tianyang maar lake was formed between 0.73 Ma to 0.87 Ma. Meanwhile, we firstly reported that the Qingtongyang maar lake and Jiudouyang maar lake were formed at 0.82 Ma and 0.81 Ma to 1.08 Ma, respectively. All of these maar lakes are formed by phreatomagmatic eruption at the Shimaoling period during the Early Pleistocene to early Middle Pleistocene in Southern China. (2) The basalts from these maar lakes belong to quartz tholeiites, which are also widely distributed around these maar lakes in the same period. The weathered products of these basalts are mainly composed by kaolinite, gibbsite and hematite. In the period of a heavy precipitation, the products of physical and chemical weathering were transported into the lake basin along with the surface runoff, which are the main sources of the sediments in these maar lakes. This result provides a fundamental understanding for the ongoing investigation of orbital monsoon precipitation variation in Pleistocene in Southern China.
Key words:Leizhou Peninsula in Southern China/
maar lake/
basalt/
K-Ar dating/
weathering
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