火山活动与构造气候旋回

火山活动是一种重要的地质现象,它的发生总是与构造运动相关联,构造运动有强有弱,持续时间有长有短,具有旋目性,火山活动同样也具有旋回性。大规模的火山喷发往往会对气候变化产生影响,而影响的程度取决于火山所处的位置和喷发的性质及程度。强烈的火山喷发将造成局部地区乃至全球气温下降,由此人们推测火山喷发多发生在冰期,然而统计资料表明,绝大多数火山喷发发生在间冰期,此时的构造运动也比较活跃,而在冰期时很少有火山喷发。至于火山喷发后在短时间内造成的降温与长时间的冰期不能相提并论。火山活动有旋回性,它影响的气候变化也具备有旋回性,这是构造气候旋回的一种表现形式。     

Tectonics and Topography of the Tibetan Plateau in Early Miocene

Early Miocene stratigraphy, major structural systems, magmatic emplacement, volcanic eruption, vegetation change and paleo-elevation were analyzed for the Tibetan Plateau after regional geological mapping at a scale of 1:250,000 and related researches, revealing much more information for tectonic evolution and topographic change of the high plateau caused by Indian-Asian continental collision. Lacustrine deposits of dolostone, dolomite limestone, limestone, marl, sandstone and conglomerate of weak deformation formed extensively in the central Tibetan Plateau, indicating that vast lake complexes as large as 100,000–120,000 km2 existed in the central plateau during Early Miocene. Sporopollen assemblages contained in the lacustrine strata indicate the disappearance of most tropical-subtropical broad-leaved trees since Early Miocene and the flourishing of dark needleleaved trees during Early Miocene. Such vegetation changes adjusted for latitude and global climate variations demonstrate that the central Tibetan Plateau rose to ca. 4,000–4,500 m and the northeastern plateau uplifted to ca. 3,500–4,000 m before the Early Miocene. Intensive thrust and crustal thickening occurred in the areas surrounding central Tibetan Plateau in Early Miocene, formed Gangdise Thrust System(GTS) in the southern Lhasa block, Zedong-Renbu Thrust(ZRT) in the northern Himalaya block, Main Central Thrust(MCT) and Main Boundary Thrust(MBT) in the southern Himalaya block, and regional thrust systems in the Qaidam, Qilian, West Kunlun and Songpan-Ganzi blocks. Foreland basins formed in Early Miocene along major thrust systems, e.g. the Siwalik basin along MCT, Yalung-Zangbu Basin along GTS and ZRT, southwestern Tarim depression along West Kunlun Thrust, and large foreland basins along major thrust systems in the northeastern margin of the plateau. Intensive volcanic eruptions formed in the Qiangtang, Hoh-Xil and Kunlun blocks, porphyry granites and volcanic eruptions formed in the Nainqentanglha and Gangdise Mts., and leucogranites and granites formed in the Himalaya and Longmenshan Mts. in Early Miocene. The K2O weight percentages of Early Miocene magmatic rocks in the Gangdise and Himlayan Mts. are found to increase with distance from the MBT, indicating the genetic relationship between regional magmatism and subduction of Indian continental plate in Early Miocene.     

Late Holocene temperature fluctuations on the Tibetan Plateau

Proxy data of palaeoclimate, like ice cores, tree rings and lake sediments, document aspects of climate changes on the Tibetan Plateau during the last 2000 years. The results show that the Tibetan Plateau experienced climatic episodes such as the warm intervals during AD 800–1100 and 1150–1400, the “Little Ice Age” between AD 1400 and 1900, and an earlier cold period between the 4th and 6th centuries. In addition, temperatures varied from region to region across the plateau. A warm period from AD 800 to 1100 in the northeastern Tibetan Plateau was contemporaneous with cooling in the southern Tibetan Plateau, which experienced warming between AD 1150 and 1400. Large-scale trends in the temperature history from the northeastern Tibetan Plateau resemble those in eastern China more than the trends from the southern Plateau. The most notable similarities between the temperature variations of the Tibetan Plateau and eastern China are cold phases during AD 1100–1150, 1500–1550, 1650–1700 and 1800–1850.     

Quantitative climate and vegetation trends since the late glacial on the northeastern Tibetan Plateau deduced from Koucha Lake pollen spectra

Quantitative information on vegetation and climate history from the late glacial-Holocene on the Tibetan Plateau is extremely rare. Here, we present palynological results of a 4.30-m-long sediment record collected from Koucha Lake in the Bayan Har Mountains, northeastern Tibetan Plateau. Vegetation change has been traced by biomisation, ordination of pollen data, and calculation of pollen ratios. The application of a pollen-climate calibration set from the eastern Tibetan Plateau to Koucha Lake pollen spectra yielded quantitative climate information. The area was covered by alpine desert/steppe, characteristic of a cold and dry climate (with 50% less precipitation than today) between 16,700 and 14,600 cal yr BP. Steppe vegetation, warm (∼ 1°C higher than today) and wet conditions prevailed between 14,600 and 6600 cal yr BP. These findings contradict evidence from other monsoon-influenced areas of Asia, where the early Holocene is thought to have been moist. Low effective moisture on the northeastern Tibetan Plateau was likely due to high temperature and evaporation, even though precipitation levels may have been similar to present-day values. The vegetation changed to tundra around 6600 cal yr BP, indicating that wet and cool climate conditions occurred on the northeastern Tibetan Plateau during the second half of the Holocene.     

A significant aegean volcanic eruption during the second millennium B.C. revealed by thermoluminescence dating

Thermoluminescence dating of four volcanic samples (material of eruption ejecta), from the island of Yiali near the Nissyros volcano in the southeastern Aegean sea, Greece, has revealed, for first time, a volcanic eruption which occurred during the 2nd millennium B.C. (c. 1460 B.C.), different from the known Santorini eruption. The interrelation between Yiali and the well-known Santorini eruption, as well as the implications of these eruptions regarding their potential impact to the Aegean prehistoric archaeology (demise of the Minoan civilization), are discussed. © 1996 John Wiley & Sons, Inc.     

An Overview on Changes of Dry/Wet Pattern in China in Decadal to Centennial Warm and Cold Periods During the Past Millennium

Revealing the multi-scale variation characteristics of the drought/flood patterns for the past millennium has been a hot spot in climate change research in recent years. It has significance for understanding and predicting the temporal and spatial differences of precipitation changes in the context of future climate warming. Based on publications on the peer-reviewed journals, here, we summarized and compared the combinations between cold/warm periods and dry/wet spatial patterns at multi-scales in China over the past millennium. The main conclusions are: although there are differences in China's dry/wet patterns in different cold and warm periods for the past millennium, the ensemble mean shows that the dry/wet patterns in eastern China in decadal or centennial warm periods are approximately "dry (South China)-wet (middle and lower reaches of the Yangtze River)-dry (Huanghuai Area)" from south to north, while in the relatively cold periods it mainly shows a "wet in east and dry in west" pattern. The climate changes from cold to warm usually lead to a drying trend in the Huanghuai Area, and a wetting trend in the Jiangnan area (especially the Yangtze River basin in Hunan and Jiangxi provinces). This shows that the "flood in south and drought in north" pattern in eastern China since the 1970s under the background of global warming may be a re-occurrence of the matching characteristics of cold/warm climate and dry/wet patterns in China for the past millennium. However, from the perspective of the longer-scale cold and warm stages, the dry/wet pattern in China tend to be "dry in the arid and semi-arid areas in western China; wet in southwestern, northern, and northeastern China; and dry in southeastern China" in the Medieval Climate Anomaly, and an opposite pattern shows in the Little Ice Age. It suggests that there are still uncertainties in the current climate reconstructions, and it also shows that the mechanism of dry/wet pattern responding to multi-scale temperature fluctuations might be extremely complicated.     

青藏高原末次冰消期气候演化特点及其与格陵兰、欧洲的异同

根据生物、湖泊及冰川地层记录,分析了青藏高原末次冰消期的气候演化特点,并将其与格陵兰、欧洲气候演化序列进行了对比分析.结果表明,末次冰消期的气候演化大致可分为两个阶段:前一阶段为暖期,但波动频繁;格陵兰、欧洲在经历了H1事件后,迅速转暖,Bolling期比Allerod期气候更为适宜;而青藏高原渐趋回暖,夏季风降水逐渐增加,存在由冰融水与降水增加所形成的高湖面,气候温湿,进入一次湖泊扩涨期;大部分记录指示Allerod期比Bolling期气候更为适宜.后一阶段为冷期,格陵兰、欧洲气候恶化并显示出有回返冰期的气候特点;青藏高原气候严酷、荒漠扩展、冰流推进、湖面下降.气候演化的这种异同性表明:格陵兰、欧洲与青藏高原气候系统彼此存在联系,特别是在冷期;而在暖期,气候演化表现出各自的特点.气候演化格局所呈现的可比性,可能是通过冷期的一致而体现的.     

Bristlecone pine tree rings and volcanic eruptions over the last 5000 yr

Many years of low growth identified in a western USA regional chronology of upper forest border bristlecone pine (Pinus longaeva and Pinus aristata) over the last 5000 yr coincide with known large explosive volcanic eruptions and/or ice core signals of past eruptions. Over the last millennium the agreement between the tree-ring data and volcano/ice-core data is high: years of ring-width minima can be matched with known volcanic eruptions or ice-core volcanic signals in 86% of cases. In previous millennia, while there is substantial concurrence, the agreement decreases with increasing antiquity. Many of the bristlecone pine ring-width minima occurred at the same time as ring-width minima in high latitude trees from northwestern Siberia and/or northern Finland over the past 4000-5000 yr, suggesting climatically-effective events of at least hemispheric scale. In contrast with the ice-core records, the agreement between widely separated tree-ring records does not decrease with increasing antiquity. These data suggest specific intervals when the climate system was or was not particularly sensitive enough to volcanic forcing to affect the trees, and they augment the ice core record in a number of ways: by providing confirmation from an alternative proxy record for volcanic signals, by suggesting alternative dates for eruptions, and by adding to the list of years when volcanic events of global significance were likely, including the mid-2nd-millennium BC eruption of Thera.     

近千年来中国气温模拟与重建资料的对比分析

依据伞球海气耦合气候模式ECHO-G近千年积分模拟结果,通过对中国气温模拟序列与重建资料进行对比分析,以验证模式对中国地区气温变化的模拟能力.结果表明模拟结果与重建资料都明显体现出了11世纪至14世纪的中世纪暖期、15世纪至19世纪的小冰期及20世纪的现代暖期3个气候特征时期,并且二者在冷暖时期的转换时间上也较吻合,模...     

青藏高原东北缘宁南盆地晚古近纪气候变化及其驱动机制

宁南盆地咸化湖相清水营组沉积记录,是研究青藏高原东北缘地区晚古近纪气候变化及其驱动机制的绝佳选择。以宁南盆地古近系清水营组为研究对象,通过野外地质调查、样品采集、石膏主量元素和锶同位素的测试,分析沉积地层记录的化学风化和古气候的变化;并通过与全球气候变化和青藏高原隆升过程的对比分析,研究青藏高原东北缘宁南盆地气候变化的驱动机制。结果表明:宁南盆地清水营组石膏中Al₂O₃/SiO₂、Al₂O₃/Ti₂O、K₂O/Na₂O和87Sr/86Sr等指标可以很好地反映晚古近纪气候变化,在38~36 Ma、34.5~33 Ma、32~31 Ma、30~27 Ma、26~23 Ma这5个时期,化学风化减弱,气候干旱化;在36~34.5 Ma、33~32 Ma、31~30 Ma、27~26 Ma这4个时期,化学风化增强,气候湿润化。晚古近纪38~26 Ma,青藏高原东北缘宁南盆地古气候变化主要受到全球气候变化的驱动;但在26~23 Ma之间,宁南盆地古气候变化受到了青藏高原隆升的重要影响。     

Magma Origin and Evolution of Tengchong Cenozoic Volcanic Rocks from West Yunnan,China: Evidence from Whole Rock Geochemistry and Nd‐Sr‐Pb Isotopes

Tengchong Cenozoic volcanics that have record key information on the tectonic evolution and mantle features of the southeast margin of the Tibetan Plateau are of great importance because of its unique eruption history spanning the entire Quaternary period. Magma origin and evolution of Tengchong Cenozoic volcanic rocks were studied on the basis of Nd-Sr-Pb isotope and major and trace element data from different eruptions in the Ma’anshan area. Different samples within one eruption show relative identical lithologies, chemical and isotopic compositions. However, the geochemical features for the five eruptions are distinct from each other. These volcanic rocks show low Mg# values (<45), moderate to high fractionation of LREEs and HREEs, and enrichment of Pb and Ba and depletion of Nb. Tengchong Cenozoic volcanic rocks were derived from an enriched mantle based on Nd-Sr-Pb isotopic studies. And lines of evidence show that crustal contamination should be involved before the eruption of different periods of Tengchong Cenozoic volcanic rocks. Older subducted components may be responsible for adakite recycling at various stages of evolution, which results in the origin of the enriched mantle source magma accounting for the isotopic features of Tengchong Cenozoic volcanic rocks. Segregated primitive magma pulsating injected into magma chamber, fractional crystallized and contaminated with crust component. Finally, magmas with distinct chemical and isotopic compositions for each eruption formed. The extension of the northeast segment of the Yingjiang tectonic belt triggered the pulsating eruption of the Cenozoic volcanics in the Tengchong area.     

Cenozoic Evolution of Sediments and Climate Change and Response to Tectonic Uplift of the Northeastern Tibetan Plateau

Through a comprehensive study of magnetostratigraphy and sedimentology of several basins in the northeastern Tibetan Plateau, we reveal that the study area mainly experienced six tectonic uplift stages at approximately 52 Ma, 34–30 Ma, 24–20 Ma, 16–12 Ma, 8–6 Ma, and 3.6–2.6 Ma. Comprehensive analyses of pollen assemblages from the Qaidam, Linxia, Xining, and West Jiuquan Basins show that the northeastern Tibetan Plateau has undergone six major changes in vegetation types and climate: 50–40 Ma for the warm-humid forest vegetation, 40–23 Ma for the warm-arid and temperate-arid forest steppe vegetation, 23–18.6 Ma for the warm-humid and temperatehumid forest vegetation, 18.6–8.5 Ma for the warm-humid and cool-humid forest steppe vegetation, 8.6–5 Ma for the temperate sub-humid savanna steppe vegetation, and 5–1.8 Ma for the cold-arid steppe vegetation. Comprehensive comparisons of tectonic uplift events inferred from sedimentary records, climatic changes inferred from pollen, and global climate changes show that in the northeastern Tibetan Plateau the climate in the Paleogene at low altitude was mainly controlled by the global climate change, while that in the Neogene interval with high altitude landscapes of mountains and basins is more controlled by altitude and morphology.     

青藏高原南部枪勇错冰前湖泊沉积记录的近千年来冰川与气候变化

以钻取自青藏高原南部大枪勇错冰前湖中的1．06m湖芯为研究对象,对沉积物样品进行了粒度、磁化率、元素含量、碳酸盐和总有机碳含量等多项指标的分析测定;在明确了沉积物来源的基础上,分析讨论了各指标变化的影响因素及其具体气候环境指示意义;结合沉积序列放射性同位素定年结果,对湖芯中各指标进行了综合对比分析,恢复了青藏高原南部枪勇错地区近千年来的冰川与气候变化。结果表明：1．06m沉积序列年代跨度为自公元11世纪前后至今的逾千年时间;沉积物主要来源于枪勇冰川融水对冰川上部沉降粉尘颗粒的携带,而沉积物的粒度、磁化率及各组分含量与区域气候条件下枪勇冰川融化强度有密切关系;自公元11世纪至今,青藏高原南部地区环境温度总体呈现波动中逐渐升高的趋势,枪勇冰川随之逐渐融化退缩。具体来说,公元11世纪初,该地区环境温度较低,枪勇冰川融化较弱;公元11世纪中叶至13世纪初,该地区气候温暖,枪勇冰川融化较强;公元14世纪开始至18世纪中叶,该地区进入小冰期,枪勇冰川融化强度显著降低;自公元18世纪中后叶至今,该地区环境温度急剧升高,枪勇冰川呈加剧融化退缩趋势。     

天池火山三期浮岩气孔形态的复杂性及其动力学成因

爆炸式喷发过程中,火山碎屑物气孔记录了挥发分出溶、膨胀和合并等信息,其大小、形态、数量密度、空间分布等局域特征是推断火山喷发动力条件的重要参考。文章基于天池火山三期喷发(50 000年前大喷发的黄色浮岩、千年大喷发的灰白色浮岩和1668年八卦庙期喷发的黑色浮岩)野外地质工作,以非线性火山喷发动力学为指导,开展了火山通道内气泡生长的流体动力学研究,揭示出岩浆流体黏性力和界面张力的共同作用对于岩浆减压和气泡生长过程的约束。在浮岩气孔结构的定量化分析基础上,进一步研究了天池火山三期喷发的浮岩气孔参数,通过气泡生长流体动力学方程得到了千年大喷发灰白色浮岩毛细管数Ca值为253, 明显高于50 000年前大喷发黄色浮岩(Ca值为94)和八卦庙期喷发黑色浮岩(Ca值为111),表明了千年大喷发曾发生过明显的成分变化,推测可能与幔源基性岩浆注入有关;而50 000年前大喷发黄色浮岩气孔不规则形态参数(1-Ω)值为0.098,大于后两期喷发(分别为0.052和0.064),可能意味着天池火山系统动力学平衡的弛豫周期变小或浮岩气泡生长受动力学、流变学改造过程减弱,这可为进一步研究天池火山活动规律提供参考。三期浮岩毛细管数Ca量级为102,气孔不规则形态参数(1-Ω)量级为10-1,从动力学上首次证实了天池火山属于普林尼型或超普林尼型喷发。     

9.4 ka以来青藏高原东北部风成沉积物色度参数变化特征及其环境演变

以青藏高原东北部泽库剖面(ZK)风成沉积物为研究对象,利用CM-5分光测色计测定了169个样品的色度参数红度(a^*)、黄度(b^*)、亮度(L^*)并计算饱和度(C^*)和色调角(h^*),在分析风成沉积物各色度参数变化特征的基础上,辅以磁化率、粒度敏感指数(SC/D)、SiO₂及Fe₂O₃含量等指标对青藏高原东北部9.4 ka以来的环境演变进行探讨。研究结果表明:(1)色度参数a^*、L^*自剖面底部向上呈先增大后减小的变化特征,h^*则自下而上先减小后增大。(2)色度参数可作为青藏高原东北部重建古气候的有效代用指标,a^*和L^*高值指示温湿环境,h^*高值指示冷干环境;各色度参数指示环境的敏感性有差异,但均对气候突变反应较为灵敏,可用于判断气候突变的典型冷暖事件。(3)9.4 ka以来青藏高原东北部的环境整体呈现为由温湿向冷干发展的态势,可分为两大阶段。9 480~4 290 a BP的温湿期,气候整体呈现向温湿方向发展的趋势,表现为较温湿→温湿→较温湿的波动;4 290 a BP至今的冷干期,气候整体不断向冷干方向发展,表现为温干→温润→凉润→冷干的变化。     

青藏高原地区过去2000年来的气候变化

依据冰芯、树轮、沉积物分析和冰川波动等各单点古气候代用资料,以及重建的综合温度变化曲线,分析了近 2000年青藏高原温度变化的整体性和区域性特征。全青藏高原综合温度曲线显示中世纪暖期（1150-1400年）、小冰期（1400-1900年）以及公元 3～5世纪冷期的存在。青藏高原温度变化具有明显的区域性特征。在 9～11世纪,青藏高原东北部以温暖为特征,而青藏高原南部和西部表现为寒冷。青藏高原南部和西部分别于1150-1400年（此时段在高原东北部表现为弱暖期）和1250-1500年经历了气候变暖。与中国东部文献记录的最新综合研究结果比较,高原东北部与中国东部的温度变化最为一致。而且,许多重大气候事件,如1100-1150年、1500-1550年、1650-1700年和1800-1850年的冷事件在高原和中国东部同时出现,而后 3次冷期与小冰期期间中国西部发生的冰川前进相匹配。     

长江三角洲千年冬温序列与古里雅冰芯比较

利用长江三角洲史料优势,重建公元820年代以来,年代级冬温序列.为测试古里雅冰芯记录的影响力,与之作比较研究.结果显示:其年代级变化背景有很好的对应关系,年代级变化有大同小异的复杂情况.舍弃量级,就年代级温度,降水升降,约有一半是同步的,且有大致对应的温湿组合.说明两地虽远隔数千公里,环境生态条件悬殊,年代级气候变化仍有响应.最后就形成响应的成因机制作初步分析。     

冰芯和气象记录揭示的青藏高原百年来典型冷暖时段气候变化特征

气候冷暖变化问题是全球科学家研究的一个聚焦点,但高海拔地区的气候变化过程尚不十分清楚,作为全球气候变化的敏感区的青藏高原更是如此. 以青藏高原北部的古里雅冰芯、唐古拉冰芯和南部的达索普冰芯、宁金岗桑冰芯δ¹⁸O记录作为温度代用指标,同时结合青藏高原西北缘的吉尔吉斯斯坦Naryn站长期气象记录和北半球同时期的气温变化进行比较,研究了过去100 a来青藏高原北部和南部的温度变化. 结果显示：青藏高原过去100 a来共出现1910年左右、1920年左右、1950年左右、1970年代4个冷期,各冷期之间对应出现4次暖期,并且变冷的程度越来越弱而变暖的程度越来越强. 其次,青藏高原气候的变冷变暖在不同地区和不同时段差异很大：从空间尺度上看,青藏高原北部变暖过程比南部更强烈;从时间尺度上看,1910年左右和1920年左右的两次变冷十分明显,但1950年左右和1970年代的两次变冷不明显. 另外,虽然有发生在1990年代早期的短暂降温过程,但与其说是一个冷事件,还不如说是一次变暖过程中的短暂停顿,随后表现为持续升温.     

火山活动与气候变化研究进展

综述了火山活动对气候影响的研究进展。不同岩浆成分及喷发类型的火山活动对气候的影响不同：中酸性普林尼（Pl inian）式火山喷发主要造成气候变冷和臭氧层破坏，它导致气候变化的时间较短，但空间范围较大；大火成岩省造成气候变化的时空范围及程度均较大，它能够导致地表温度、海平面大幅度变化，最终引起生物灭绝；中小规模玄武质裂隙式喷发主要造成火山盆地内气候较大幅度变化，但对气候影响的持续时间较短，主要气候效应是导致附近地区温度快速下降和形成酸雨。简要阐述了第四纪火山活动的特点。     

Geomorphic and chronometric evidence for high lake level history in Gahai Lake and Toson Lake of north‐eastern Qaidam Basin,north‐eastern Qinghai–Tibetan Plateau

Palaeoshorelines, highstand lacustrine sediments and lakeshore terraces are preserved around saline lakes in the arid Qaidam Basin. Previous research indicates that the chronology of a mega‐paleolake in the Qaidam Basin during the late Pleisotocene is controversial. Here we report quartz optically stimulated luminescence (OSL) age estimates of highstand lacustrine sediments, shoreline features and geomorphic exposures that contribute to a revision of the lake level history of Gahai and Toson lakes in the north‐eastern Qaidam Basin, on the northeastern Qinghai–Tibetan Plateau (QTP) margin. The results imply that: (i) high lake levels at Gahai and Toson lakes based on quartz OSL dating occurred at 85–72, 63–55, 31, 5.4 and 0.9–0.7 ka, probably corresponding to periods of warm and wet climate; (ii) periods of high lake levels are almost synchronous with other lakes on the QTP (e.g. Qinghai and Namco lakes), with the highest late Pleistocene levels occurring during Marine Oxygen Isotope Stage 5; and (iii) highstand phases on the QTP are out of phase with those of low‐latitude lakes in the southern hemisphere, possibly driven by solar insolation variability in the low‐latitude region. Copyright © 2012 John Wiley & Sons, Ltd.