大兴安岭中段索伦地区林西组岩石地球化学特征与沉积构造环境

大兴安岭中段林西组是重要的含烃源岩层位,烃源岩的形成与生烃母质生物活动和埋藏时的古气候、古构造、古环境息息相关。通过岩石地球化学分析可以恢复林西组沉积时期的气候与构造环境,利用Sr、Li、Ga含量、Sr/Ba值、U/Th值、δU及Sr/Cu值,从古盐度、氧化还原环境、古气候等方面分析了索伦地区林西组的沉积环境,认为林西组沉积时可能经历了中等—较强风化后的再沉积作用,总体为淡水—微咸水的氧化环境,气候温湿;Al₂O₃/(Al₂O₃+Fe₂O₃)值、K₂O/Na₂O-SiO₂关系以及稀土元素特征表明：林西组形成于靠近大陆岛弧的活动大陆边缘,由早期弧后盆地的海陆过渡相半咸水环境向陆相的淡水环境演变,有利于有机质的富集和保存,是寻找烃源岩的有利层位。研究成果可为该区烃源岩勘查提供指导。     

长江三角洲古河谷区冰后期孢粉组合及古气候意义

依据长江三角洲古河谷区典型钻孔CSJA6孔中冰后期孢粉分布情况,结合有孔虫分析以及6个样品的AMS 14C年龄,自下而上初步建立了冰后期3个有时间标定的孢粉组合,分别为:Ⅰ. Quercus-Lipuidambar-Artemisia-Polypodiacea组合,时代属于早全新世;Ⅱ. Quercus-Castanopsis-Cyperaceae-Pteris组合,时代属于早-中全新世;Ⅲ. Quercus-Ulmus-Artemisia-Polypodiacea组合,时代属于中-晚全新世.3个孢粉组合带所反映的古气候演变过程为凉干-热湿-温干,这与中国的气候大环境较为一致,且与本区前人研究成果亦做了相应的对比,依然具有较好的可对比性.     

全球变化研究中的生物气候指标

在大气科学、地学和生态学的长期研究中,科学家们经常使用年与季节的单一和综合气候指标,来表达气候及其变异特征,并预测气候与环境的关系和未来变化。在近期的全球变化研究中,尤其是植被模型领域,科学家们较多利用生物气候指标来模拟和分析植被结构、功能与环境的定量关系,包括年均温、最冷月和最热月均温、极端低温、年降水及其季节性分配、生长度日（积温）GDD₀和GDD₅,以及各种干旱或湿润指数,比如α指数（实际蒸散与可能蒸散的比率）、Palmer干燥度指数（PDSI）和标准化降水蒸散指数（SPEI）等。然而,部分计算较复杂的指标在古生态学和古植物学领域,尤其在基于孢粉数据定量重建古气候时,使用尚不频繁。本文在简介生物气候指标及其对物种和植被分布的控制原理之后,重点介绍全球植被模型与古气候定量重建中常用的一些生物气候指标,包括其原理、计算方法、优缺点及其应用举例,并列举一些易获取的气候数据库供下载使用,如CRU和WorldClim全球气候数据库,来自中国气象数据网的各种元数据和插值数据,以及来自中国生态系统研究网络数据共享系统的中国陆地生态信息空间气象数据库等。

     

巴丹吉林沙漠全新世环境记录的年代校正与古气候重建

巴丹吉林沙漠地处东亚夏季风区的西北缘,是认识东亚季风演变及其区域响应的窗口。文章在系统研究前人工作的基础上,对环境记录的年代进行了新的校正,并重建了全新世环境演变的历史。分析结果显示,巴丹吉林沙漠在早全新世开始出现高湖面,早中全新世在湖区广泛出现高湖面和淡水环境并在沙漠东北缘发育了古土壤,晚全新世时湖泊水位下降,沉积地层以风成砂为主。巴丹吉林沙漠全新世环境变化总体上可分为3个阶段: 晚更新世末至早全新世初气候干旱; 在10.0cal.kaB.P.左右气候由干向湿快速变化,并在8.5~4.0cal.kaB.P.期间气候最为湿润,但同时存在短期的干湿波动; 4.0cal.kaB.P.以来气候总体干旱,但在2.2cal.kaB.P.左右出现短期的湿润。巴丹吉林沙漠全新世气候变化反映了该地区在早全新世东亚夏季风降水明显增强,中全新世季风降水较强,晚全新世季风降水减弱,同时具有短时期的不稳定性。10.0cal.kaB.P.以来巴丹吉林沙漠气候总体由湿润向干旱变化,应与北半球全新世以来太阳辐射的持续减弱有关。     

红寺堡盆地晚更新世沉积特征及古气候背景

萨拉乌苏组、水洞沟组和马兰黄土是青藏高原东北缘弧形构造带乃至鄂尔多斯高原西部晚更新世发育的3套重要的沉积层系,但三者之间的沉积接触关系一直存在着争议。以红寺堡盆地为研究对象,在路线地质调查的基础上,结合砂岩石英颗粒表面扫描电镜分析及黏土矿物含量分析,查明3套地层之间的纵横向变化关系,确定红寺堡盆地晚更新世接受黄土沉积的最早时限及所处的古气候背景。研究认为：红寺堡盆地萨拉乌苏组与水洞沟组和马兰黄土之间是上下叠置关系,湖盆中心萨拉乌苏组上覆水洞沟组,湖盆边缘萨拉乌苏组上覆马兰黄土;水洞沟组与马兰黄土之间为同时异相的相变关系,在湖盆中心为湖相沉积,在湖盆边缘地形相对较高的部位,则为同时期的风成黄土沉积;红寺堡盆地接受黄土沉积的最早时限为萨拉乌苏组沉积末期,萨拉乌苏组顶部局部可见风成沉积的柱状节理,砂岩石英颗粒表面具有水成和风成兼顾的特征。红寺堡盆地晚更新世经历了温暖湿润-寒冷干旱-温暖湿润-寒冷干旱的气候变化过程,在萨拉乌苏组二段与水洞沟组中部,伊利石和绿泥石含量表现为相对低值,而蒙脱石和高岭石含量表现为相对高值,蒙脱石含量明显增加,但同时又有高岭石矿物的出现,总体上反映了温暖湿润的古气候特征,两期温暖湿润的环境分别对应于深海氧同位素曲线MIS3与MIS5阶段,具有全球对比意义。研究成果为鄂尔多斯高原西部生态环境的演化及综合治理提供了基础地质依据。     

龙江盆地西缘中侏罗世孢粉植物群及其对古气候的指示

对产于龙江盆地中侏罗统万宝组含煤地层中的孢粉化石进行了系统研究,共识别出中侏罗世孢粉化石45属73种,蕨类植物孢子15属16种,裸子植物花粉30属57种,自下而上建立了Alisporites-Chasmatosporites-Cyclogranisporites,Chasmatosporites-Piceites-Cyclogranisporites及Cyclogranisporites-Baculatisporites-Protopinus3个孢粉组合。该孢粉植物群以裸子植物花粉占优势,蕨类孢子次之,其中,裸子植物花粉以松柏类植物的双囊花粉和苏铁类、本内苏铁类、银杏类植物的单沟花粉为主。通过对龙江盆地万宝组孢粉植物群的组成分析,其时代应为中侏罗世。结合对该地质时期的植物群生态环境的研究,万宝组孢粉植物群反映了由半湿润到湿润的暖温带-亚热带的气候特点,并存在一定低矮山地的古环境。     

Stratigraphy and palaeoenvironmental development of Quaternary coarse clastic beach deposits at Plage de Mezpeurleuch,Brittany (France)

Quaternary deposits are described from well‐exposed sections in cliffs at Plage de Mezpeurleuch, Finistère, Brittany (France). The general lithostratigraphic sequence comprises Holocene perched dune sand, calcrete and palaeosol overlying Weichselian head and coarse clastic palaeobeach units attributed to the last interglacial (Eemian–isotope substage 5e). A lower and an upper palaeobeach, separated by a thin head deposit, are reported resting on an irregular palaeorock platform eroded in Hercynian granite. From a comparison with modern coastal environments a palaeoenvironmental interpretation of the palaeobeach deposits is made. Erosionally bounded facies of the lower palaeobeach, are considered to be a transgressive sequence preserved by drowning associated with a rapid rise in relative sea‐level. Its subsequent abandonment is attributed to a relative sea‐level fall, which allowed a terrestrial environment to develop briefly. Facies of the upper palaeobeach however indicate a prograding shoreline developed during a prolonged period of relatively stable sea‐level. These sea‐level observations are in good agreement with other evidence for a brief widespread intra‐Eemian cold event. Copyright © 2001 John Wiley & Sons, Ltd.     

An Early Pleistocene hippopotamus from Westbury Cave,Somerset, England: support for a previously unrecognized temperate interval in the British Quaternary record

Although fossil assemblages from the late Early Pleistocene are very rare in Britain, the site of Westbury Cave in Somerset, England, has the potential to address this gap. The mammal fossils recovered previously from the Siliceous Member in Westbury Cave, though few in number, have hinted at an age for the deposits that is as yet unparalleled in Britain. Here, we describe the first bona fide occurrence of Hippopotamus in the British Early Pleistocene, discovered during recent reinvestigation of the Siliceous Member. The hippo fossil indicates a refined biochronological age of ca. 1.5–1.07 Ma for the Siliceous Member and a palaeoclimate that was warm and humid, which accords well with previous palaeoenvironmental inferences. A synthesis of late Early Pleistocene hippo occurrences suggests that the Siliceous Member hippo may have been part of an early colonization of north-west Europe by these megaherbivores, possibly during MIS (Marine Oxygen Isotope Stage) 31. Alternatively, it evidences a currently cryptic northward migration during an even earlier temperate phase. In either case, the Siliceous Member is likely to represent a warm period that has not been recognized previously in the British Quaternary record.     

Lateglacial and Holocene palaeoenvironments at Sierra La Madera,northwestern Mexico: Sharp signals of Younger Dryas and North American monsoon

During the last glacial termination, the climate system experienced intense global variations whose causes and impacts are not fully defined, particularly for low latitudes. The northwestern Mexico Sky Islands present a climate-sensitive ideal setting to record palaeoecological and palaeoclimatic changes due to their physiographic complexity and location in the ecotone between temperate and tropical ecosystems. High-resolution pollen analysis and a detailed sedimentological study were conducted at the Ciénega Tonibabi tropical thorn scrub site. The 15 540–0 cal a bp nearly continuous record shows that the North Atlantic Ocean did have a cold and humid climatic influence during the glacial stages of the end of the Pleistocene, including a sharp pulse during the Younger Dryas. However, a shift to the Pacific Ocean influence occurred during the Holocene, which led to the development of the El Niño conditions prevailing today. Colder and warmer phases follow one another with higher or lower winter precipitation, including a sharp Bølling–Allerød and development and intensification of the North American monsoon. They are reflected in hydrological changes as well as in the advances, retreats and intermingling of coniferous forests and tropical thorn scrub.