Summer precipitation for the England and Wales region, 1201–2000 ce,from stable oxygen isotopes in oak tree rings     

Neil J. Loader  Giles H. F. Young  Danny McCarroll  Darren Davies  Daniel Miles  Christopher Bronk Ramsey 《第四纪科学杂志》2020,35(6):731-736

Oxygen isotope ratios from oak tree rings are used to extend the May–August precipitation totals of the England and Wales precipitation series back to 1201 ce. The agreement between instrumental and reconstructed values is unusually strong, with more than half of the variance explained and standard verification tests passed. The stability of this relationship is confirmed using split-period calibration and verification. This allows the reconstruction to be variance-scaled to the full length of the instrumental series back to 1766. Direct comparison with historical reports of very wet and dry summers show good agreement. Near-constant replication, with a minimum of 10 timbers sourced from historic buildings across central southern England ensures signal strength does not change over time. Summers during the late 20th century appear anomalously dry and those of the 21st century very close to the pre-20th century average with no evidence in the record of prolonged ‘megadroughts’ across England and Wales.  相似文献   

深海现代沉积有机质碳同位素组成变化的古气候证据   总被引：2，自引：0，他引：2  

段毅  罗斌杰 《海洋地质与第四纪地质》1998,18(4):53-58

分析了南沙海洋深海连续沉积岩心剖面中有机碳同位素,研究了只有机质碳同位素组成变化因素及其与古气候旋回的关系,各种有机地球化学指标综合判识表明,该岩心剖面沉积有机质碳同位素组成变化未受有机质性质和成岩作用的影响,主要与古气候变迁关系密切。其ε＾１３Ｃ低值段对应于晚第四纪末次冰期,高值段对应于末次间冰期。  相似文献   

The influence of organic sources and environments on source rock deposition during the periods of Cretaceous–Eocene and Oligocene–Miocene,northern Kalimantan     

Lei Lan  Youchuan Li  Zhigang Zhao  Shuchun Yang  Qing Lin  Weilai Zhang 《海洋学报(英文版)》2023,42(3):54-64

The sedimentary system of Kalimantan has undergone significant development since the Oligocene. Previous research have largely ignored the capacity of the Cretaceous–Eocene sediments to produce hydrocarbons,focusing instead primarily on the Oligocene–Miocene coal as the principal source rocks. Shales and coals from the outcrops in the northern margin of Kalimantan were analyzed with palynological and geochemical methods to characterize the palaeoenvironmental and palaeoecological differences bet...  相似文献   

陕西铜川晚三叠世孢粉植物群及其环境意义   总被引：4，自引：3，他引：1  

江德昕  王永栋  魏江 《古地理学报》2006,8(1):23-33

本文基于陕西铜川地区上三叠统永坪组和瓦窑堡组发现的孢子花粉化石28属46种的研究,建立了研究区晚三叠世早期至晚期孢粉植物群。根据孢粉植物群的特征探讨了该区晚三叠世古生态、古气候、古地理和沉积环境。研究结果认为研究区晚三叠世早期古气候和沉积环境有利于石油的形成,晚期古气候和沉积环境有利于煤炭和天然气的形成。  相似文献   

三峡库区川东-鄂西早-中侏罗世地层的精细对比及沉积环境变化   总被引：2，自引：0，他引：2  

孟繁松  李旭兵 《华南地质与矿产》2004,(3):59-66

根据地层层序、岩性特征和化石组合带所提供的时代信息,三峡东部早-中侏罗世香溪组、泄滩组下段、上段和陈家湾组应分别与三峡西部自流井组珍珠冲段下-中部、珍珠冲段上部-东岳庙段、马鞍山段-大安寨段和新田沟组精细对比。指出三峡库区早-中侏罗世古地理大致呈现由河道、河漫湖泊沼泽相含煤沉积→典型的湖泊相沉积→河流与湖泊相周期性交替沉积的变化规律。在分析岩组特征和植物所指示的气候基础上,推测早-中侏罗世气候的变化趋势是,由炎热潮湿逐渐变为炎热干旱。  相似文献   

Middle Devensian (Weichselian) coleopteran assemblages from Earith,Cambridgeshire (UK) and their bearing on the interpretation of ‘Full glacial’ floras and faunas     

G. Russell Coope 《第四纪科学杂志》2000,15(8):779-788

Macroscopic plant remains from middle Devensian organic lenses, exposed in a gravel pit near Earith in the valley of the River Great Ouse in Cambridgeshire, were the object of an extensive study by Frances Bell in the late 1960s, which has been much referred to in the subsequent literature. The floras from each sampling site have been taken to be characteristic of Full‐glacial conditions in general. Coleopteran assemblages taken at the same time from exactly the same sampling sites show that at least two periods of markedly different climatic regimes were involved. The first of these (? the older) was characterised by a cold and continental climate with mean July temperatures at or below 10d°C and mean January/February temperatures about −23°C. The second climatic regime was characterised by warm summers with mean July temperatures about 16°C and mean January/February temperatures close to −5°C. In spite of this temperate climate, pollen analysis shows that no trees grew in Britain at that time. This treeless but temperate episode in the middle of the Devensian (Weichselian) is discussed in the context of coleopteran assemblages from other sites in southern England that probably date from the same period. Copyright © 2000 John Wiley & Sons, Ltd.  相似文献   

Recent lake level variations in Lake Haubi, central Tanzania, interpreted from pollen and sediment studies     

Mats G. Eriksson  Raymonde Bonnefille  Forename Surname  Séverine Lafon 《Journal of Paleolimnology》1999,22(4):457-473

Variations in pollen assemblages and in physical and chemical composition of a dated sediment record from the small Lake Haubi in north central Tanzania, reveal lake level fluctuations since the late 19th century. Lake Haubi changed from a seasonally inundated swamp to a lake in the beginning of the 20th century. With the exception of 1942-44, when it dried out completely, it remained water filled until 1994 when it again turned into a swamp. The lake level fluctuations in Lake Haubi are largely in phase with fluctuations of the larger East African lakes levels during the 20th century, and are therefore interpreted as being mainly controlled by regional climatic fluctuations. However, the initial formation of Lake Haubi at the turn of the century was likely due to local catchment specific causes, e.g. changes in land use, as the rapid increase in the water level at this time does not correspond to other lake level records from the region.  相似文献   

钱塘江下切河谷SE4孔晚第四纪沉积环境与古气候演化^*          下载免费PDF全文

夏长发  张霞  林春明  黄舒雅  江凯禧  周学谦 《古地理学报》1999,24(3):433-448

综合钱塘江下切河谷SE4孔岩心观察和描述及粒度、孢粉、测年等分析数据,探讨了钱塘江下切河谷晚第四纪沉积环境和古气候演化,揭示了其气候变化机制下沉积响应的具体过程。研究表明SE4孔晚第四纪沉积物自下而上包括河床亚相、河漫滩亚相、古河口湾相、浅海亚相和现代河口湾相5套沉积。研究区晚第四纪以来古植被和古气候演化分为6个阶段:第一阶段植被类型为阔叶树为主的针阔混交林—草原,气候温和偏湿,沉积了河床和河漫滩亚相;第二阶段为落叶栎稍多的针阔混交林,气候温和湿润,沉积了古河口湾相和浅海亚相;第三阶段为针阔混交林,气候温暖湿润,浅海亚相沉积发育;第四至第六阶段植被类型经历了针阔混交林—草原、针阔混交林、针阔混交林—草原的交替,气候经历了温和偏干、温和偏湿、温和偏干的变化,现代河口湾相沉积发育。  相似文献   

梁子湖沉积物有机质碳同位素特征及其古气候指示意义   总被引：2，自引：0，他引：2  

金芳  黄俊华  汤新燕  阮小燕  祁士华 《地质科技情报》2007,26(3):13-18

分析了梁子湖8.35 kaB.P.以来沉积物中有机质δ(13C)的组成特征,并与代表印度洋季风的四川红原泥炭δ(13C)序列及代表东亚季风的长白山哈尼泥炭δ(13C)序列进行了对比,探讨了早全新世以来不同阶段的气候特点及古东亚季风与印度洋季风对该区的影响.研究表明,梁子湖在其形成演化过程中存在两种典型的湖泊沉积环境.5.98 kaB.P.以前δ(13C)值偏负,气候温暖湿润,有机质以湖泊内源水生生物为主,δ(13C)值与湖泊生产力有关.其早期东亚季风对该区的影响占较大优势.全新世大暖期中期(5.98～3.67 kaB.P.),气候持续暖湿,温度与降水达到顶峰,δ(13C)值也达到序列中的最小阶段,其δ(13C)值偏负与浮游生物生产力的增加有很大的关系.3.67～3.29 kaB.P.是气候突变期,δ(13C)值变幅达6‰.3.29 kaB.P.以后δ(13C)值逐渐偏正,气候逐渐变冷干,沉积环境发生较大变化,有机质以陆源C3植物碎屑为主,此时期东亚季风开始加强,印度洋季风持续减弱,但该区受印度洋季风影响更强烈.研究显示,东亚季风与印度洋季风强弱转换和时空迁移的影响对长江中游地区气候环境的演化具有重要作用.  相似文献   

古气候变化的石笋同位素记录研究——以桂林盘龙洞为例   总被引：17，自引：4，他引：17  

覃嘉铭 《地球学报》1997,18(3):255-260

本文以桂林盘龙洞的研究工作为例，选择大型石笋剖面，在沉积学分析学研究的基础上，采用目前最先进的测年技术———ＡＭＳ１４Ｃ法，配合Ｕ系及稳定同位素地球化学综合手段，系统提取气候信息，建立了桂林地区３．６万ａ来气候变化的基本模式。该区末次冰期３．２～３．６万ａ时，年平均气温最低８～９℃。全新世在总的暖和、潮湿气候背景下，可划分出由暖到冷的３个气候旋回，每个旋回持续约３０００ａ左右，暖期年平均气温高于现今３～４℃，冷期低于现今３℃左右，可鉴别的次一级冷期可与我国５０００ａ物候记录资料进行对比。  相似文献