摘要
中新世气候变化特征是新生代以来全球整体变冷过程的一个特例,特别是早-中中新世气候变暖更是显著地改变了变冷的节奏,变暖在中中新世气候适宜期(MMCO)达到顶峰;中中新世气候转型(MMCT)开始又回归了“正常的”整体变冷趋势。MMCO作为全球变冷的“扰动”事件,对全球变暖背景下气候变化趋势预测的准确性有重要的指示意义,但是它对于中国区域气候的影响仍然不清。本研究对柴达木盆地花土沟剖面20.0~11.3 Ma之间(厚度3135 m)以约0.1 Ma间隔取样,分析长石类矿物中钾长石、斜长石含量等开展区域化学风化研究,试图找到矿物组成变化对于MMCO及MMCT的响应。结果显示,沉积物斜长石和钾长石的含量明显低于地表平均含量,而且粉砂质颗粒中钾长石/斜长石值变化范围为0.24~1.08,平均值0.75,明显高于地表物质中两种矿物的平均比值(0.32);其变化曲线记录了中新世早期全球变暖→MMCT整个过程区域环境变化的痕迹。中新世早期随全球气温的升高,柴达木盆地土壤水分含量提高,在17.4~15.0 Ma之间达到高峰,MMCT开始后区域降水明显降低,钾长石/斜长石值同时受到区域构造运动引起的物源变化的影响。研究显示,上地壳含量最高的长石类矿物在沉积物中的变化特征,能够敏感地指示受土壤湿度影响的化学风化程度,也就能够在一定程度上暗示区域气候变化过程及构造运动特征;而长石类矿物在上地壳的普遍存在也为进行气候变化全球对比及数据同化等提供了一种简单、经济、便捷的方法。
Climatic change in the Miocene Epoch represents one of the special scenarios in the Cenozoic global cooling,of which the warming trend during Early to Middle Miocene had interrupted the natural rhythm on earth and climaxed in the Middle Miocene Climatic Optimum(MMCO).The Middle Miocene Climatic Transition(MMCT)following MMCO had turned the global climate into its previously normal cooling track.As the reversal event of the global cooling,even if MMCO could shed light on improving fidelity of climatic prediction under the global warming condition in the future,its impacts for regional environmental changes in the geological time scale remain unknown.This study focuses on mineral records to MMCO and MMCT based on 101 samples analysis to potassium feldspar and plagioclase concentrations at interval of about 0.1 Ma for the Miocene sediments from the Huatugou section(from 38°22.0'N,90°52.9'E to 38°25.6'N,90°53.8'E)in the northwest Qaidam Basin,which was assigned to 21.3~11.3 Ma(thickness 3135 m)according to magnetostratigraphy and biostratigraphy previously.The Miocene is composed of the Xiayoushashan and Shangyoushashan formations.The former contains well sorted gray to red-brown silty clay,siltstone and fine-grained sandstone intercalated with sparse conglomerate layers,with numerous thin marl layers and abundant fossils including fish pieces and leaves in its lower parts.It could be interpreted to lacustrine sediments.It conformably overlies the Shangganchaigou Formation and lies conformably beneath the latter too.The latter is characterized by gray to brown,poorly sorted,clast-supported conglomerate intercalated with sparse sandstone and siltstone,which shows a general upward coarsening sequence.Large-scale planar cross-stratification and grain-sized suggest it was deposited in fluvial environment.Data results reveal that concentration of potassium feldspar and plagioclase are lower than their averages in the Earth surface.The feldspar;plagioclase values for silt particles in Xiayoushashan and Shangyoushashan
作者
常宏
秦秀玲
关冲
李乐意
罗家馨
CHANG Hong;QIN Xiuling;GUAN Chong;LI Leyi;LUO Jiaxin(State Key Laboratory of Loess and Quaternary Geology,Institute of Earth and Environment,Chinese Academy of Sciences,Xi'an 710061,Shaanxi;CAS Center for Excellence in Quaternary Science and Global Change,Xi'an,710061,Shaanxi;University of Chinese Academy of Sciences,Beijing 100049;Xi'an Center of Mineral Resources Survey,China Geological Survey,Xi'an 710061,Shaanxi;Xi'an Institute for Innovative Earth Environment Research,Xi'an 710061,Shaanxi)
出处
《第四纪研究》
CAS
CSCD
北大核心
2024年第6期1590-1600,共11页
Quaternary Sciences
基金
国家自然科学基金项目(批准号:42372221)
科技部第二次青藏高原综合科学考察研究项目(批准号:2019QZKK0707)共同资助。
关键词
新生代全球变冷
钾长石
斜长石
化学风化
中中新世气候适宜期
中中新世气候转型
构造运动
Cenozoic global cooling
potassium feldspar
plagioclase
chemical weathering
Middle Miocene Climate Optimum
Middle Miocene Climate Transition
tectonic movement
