青藏高原东北部泥炭沉积粒度与元素记录的全新世千年尺度的气候变化

通过对青藏高原东北部共和盆地泥炭沉积的粒度与地球化学元素分析, 重建了区域全新世千年尺度的气候变化过程. 结果显示: 10.0~8.6 cal ka BP区域暖湿程度逐渐增加, 但在8.6~7.1 cal ka BP气候相对寒冷干燥, 7.1~3.8 cal ka BP 暖湿程度总体上为全新世最佳, 但也出现明显的气候波动, 3.8~0.5 cal ka BP气候向冷干方向发展, 0.5 cal ka BP以来气候又逐渐转向暖湿. 这一特征与中国东部季风区的气候变化有很好的一致性. 此外, 区域全新世气候变化过程中存在10次千年尺度的寒冷事件, 并与高原冰芯、 湖泊、 泥炭和风成沉积记录的古气候变化, 甚至与北半球高低纬度的气候变化都具有良好的可比性. 因此, 认为区域全新世气候变化具有"季风模式"与"千年尺度震荡"的双重特点.     

我国低纬季风区晚冰期以来水文变化：南岭东部高分辨率湖沼沉积记录

南岭东部定南大湖盆地湖沼相沉积高分辨率记录揭示了16.0cal ka BP以来的水文变化过程。由于该盆地主要以降水补给为主,故其水文变化过程是该地区气候与环境变化的忠实反映。多气候代用指标揭示晚冰期以来的Oldest Dryas、Blling、Older Dryas、Allerd和Younger Dryas等短尺度气候快速变化事件。10.0～6.0cal ka BP期间,该地区降水最为丰沛,暗示了夏季风在该时期最强盛,但在约9.7～9.4cal ka BP和8.8～8.2calka BP前后出现过降水骤减事件;在6.0～3.0cal ka BP期间,研究区降水显著减少,夏季风势力明显减弱。大湖盆地全新世气候变化记录与我国低纬度区域近年来的研究记录具有很好的一致性,说明低纬地区全新世适宜期应在10.0～6.0cal ka BP期间。在全球气候变化对比上,大湖盆地降水减少时期大多对应于北大西洋深水流或温盐循环减弱时期,也对应于北大西洋浮冰砾高峰时期;早全新世(10.0～6.0cal ka BP)降水丰沛期对应于北大西洋深水流加强时期;表明北大西洋深水流变化所导致的高低纬地区热量差异与我国低纬季风区过去气候变化有某种遥相关。此外,大湖盆地晚冰期以来气候变化趋势与北半球夏季太阳辐射量变化趋势吻合。因此笔者认为东亚低纬季风区晚冰期以来气候变化机制与太阳辐射量变化、大洋温盐循环等有关。     

末次盛冰期以来青藏高原东北部共和盆地气候与环境变化研究进展

青藏高原东北部共和盆地气候与环境变化文献分析认为:末次盛冰期(14 C年龄14ka BP或16cal ka BP之前)地层沉积主要为风成砂和黄土,冰缘地貌发育,气候寒冷干燥,植被可能为干旱荒漠或荒漠草原;末次冰消期(14 C年龄14ka BP或16 cal ka BP-Younger Dryas,缩写YD事件)地层发育古土壤,湖泊水位明显上升,并显著的捕捉到冷暖事件(Blling-Allerd,缩写B/A、YD)的信息,气候趋于温暖湿润,对应植被为荒漠草原;全新世8.5ka BP(14 C年龄)之前区域温度和湿度不同程度增加,湖泊水位较高,地层发育古土壤,植被为荒漠草原或干草原;8.5～7.0ka BP(14 C年龄)风成砂出现,古土壤发育中断,气候寒冷干燥,为全新世新冰期第一期;7.0～3.0ka BP(14 C年龄)古土壤显著发育,高水位湖面出现,水热组合达到全新世最佳,植被向干草原方向演化,但期间也存在千–百年尺度的冷事件(全新世新冰期第二期);3.0ka BP(14 C年龄)以来气候向温凉(寒冷)干燥方向发展.太阳辐射等外部因素变化并触发地球系统内部各个圈层之间相互作用是区域气候、环境变化的主要驱动力.同时,对研究现状进一步剖析,阐明其存在的问题,并提出气候、环境变化研究的发展方向.     

距今220 ka以来大同盆地沉积物磁化率反映的气候变化

大同盆地地处我国季风影响的北部边缘, 第四纪以来盆地内发育厚层的河湖相地层, 其上覆盖马兰黄土或全新世沉积, 蕴含着丰富的气候环境变迁信息, 是研究气候环境变化的理想场所. 在对盆地内地层考察的基础上, 对晚近地质时期河湖相与风成相互层沉积剖面的磁化率、粒度变化进行了分析. 结果表明: 220 ka BP以来大同盆地气候变化经历了中更新世(220~199 ka BP)暖湿期、中更新世(199~138 ka BP)干冷期、末次间冰期(138~71 ka BP)暖湿期、末次冰期(71~11 ka BP)干冷期、全新世(11 ka BP至今)频繁的干冷暖湿波动变化过程, 每个阶段仍有次一级的气候波动. 大同盆地这种气候变化与深海氧同位素以及我国北方萨拉乌苏河地区、岱海等地揭示的气候变化有很好的对应, 反映出本区气候变化是对全球冰期-间冰期气候波动的响应.     

台湾头社盆地湖沼相沉积孢粉记录的6.2~1.3 cal ka BP以来气候研究

头社盆地位于中国台湾省中部,东亚季风区的最前沿,对东亚季风的响应十分敏感,研究其中晚全新世以来古植被、重建古气候序列,探讨其气候与东亚夏季风的关系具有重要的科学意义。文章对头社盆地泥炭—湖泊沉积的AMS14C测年、体积磁化率测试的基础上,基于孢粉记录,重建晚全新世来植被变化,恢复古气候。结果表明全新世中晚期以来分六个阶段：6.2~6.0 cal ka BP,气候凉干,植被类型是亚热带常绿阔叶林;6.0~4.0 cal ka BP,气候转暖湿,植被类型为含较多热带成分的亚热带常绿阔叶林;4.0~2.2 cal ka BP,气候相对凉干,植被类型转为亚热带常绿阔叶林;2.2~1.9 cal ka BP,气候又变暖湿;1.9~1.7 cal ka BP,气候快速冷干事件,森林退化;1.7~1.3 cal ka BP,气候重转温暖湿润,植被类型为接近现代的沼泽草原。整体上6.2~2.2 cal ka BP的气候变化是由温暖湿润向温凉干燥转变的趋势,这是全新世中晚期以来的太阳辐射量减少所导致的,太阳辐射量的减少导致热带辐合南移,进而导致东亚夏季风减弱,而2.2 cal ka BP之后气候波动较大,可能是在东亚夏季风减弱的背景下,ENSO活动加强与人类活动的干扰下耦合的结果。     

青藏高原（格尔木-亚东）冰缘现象及其气候意义

冰缘地貌与沉积是冰冻圈环境变化的载体,对其开展深入研究对了解青藏高原地表过程与过去气候变化,具有重要意义。基于青藏高原（格尔木-亚东）冰缘地貌和沉积野外记录和实验分析,获得以下认识：格尔木在LGM时多年冻土至少下限到达海拔2 900 m,年均气温降至< -4 ℃,比现在至少低9 ℃,气候寒冷干燥;冰消期和全新世存在极端干冷的气候事件,可能存在地面温度< -10 ℃的冬季迅速降温气候期。楚玛尔、那曲谷露和纳木错的冰楔假型分别记录了末次冰期冷期多年冻土扩张,亚东古砂楔记录了早全新世冷事件。西藏羊八井泥炭沉积剖面孢粉和测年揭示,该区自新仙女木事件以来经历了严寒（12.8~9.8 ka）、暖湿（9.8~5.0 ka）、干冷（5.0 ka至今）的气候阶段。青藏高原（格尔木-亚东）广泛发育的冻融褶皱、成层坡积、风沙沉积等,是古环境重建的重要佐证,具有刻画冷暖-干湿的意义。     

末次冰消期以来赛里木湖沉积记录的气候突变

末次冰消期以来的气候突变事件的时空变化特征及其区域响应是古气候环境变化研究的重要内容,然而亚洲中部干旱区末次冰消期以来的气候突变记录较少,尤其缺少末次冰消期期间快速转暖过程的区域响应.本研究通过对位于亚洲中部干旱区的新疆西天山中部亚高山湖泊赛里木湖湖心采得的长300 cm的SLM2009钻孔沉积物的碳酸盐含量和粒度变化特征的分析,在 14 个 AMS 14C测年数据的基础上,探讨了末次冰消期约23. 4 cal. ka B. P.以来亚洲中部干旱区的气候突变事件记录及其区域响应过程.结果表明:赛里木湖湖心钻孔沉积物完整记录了 H1 ( 17. 5 ~ 15. 2 cal. ka B. P.)、 YD ( 12. 6 ~ 11. 7 cal. ka B. P.)冷事件以及 B-A ( 15. 2 ~12. 9 cal. ka B. P.)暖事件等末次冰消期气候突变事件以及全新世以来的10. 5 ka、 8. 2 ka、 5. 5 ka、 4. 2 ka、 2. 8 ka和小冰期冷事件,这与亚洲中部干旱区已有的气候突变事件记录相吻合,表明末次冰消期以来亚洲中部干旱区具有相似的气候突变演化模式.同时这些气候突变事件与高纬冰芯以及低纬石笋氧同位素记录的一致性则表明气候突变具有全球性影响,受相同的成因机制因素控制.     

内蒙古克什克腾旗浩来呼热古湖泊全新世以来的环境演变

利用位于中国北方季风尾闾区的浩来呼热古湖泊沉积物中的硅藻化石重建了全新世以来的环境演变历史。根据硅藻组合的变化,可将浩来呼热古湖泊全新世以来的环境演变过程划分为6个阶段:阶段Ⅰ(12.1～11.5cal ka BP),气候以寒冷为主;阶段Ⅱ(11.5～8.6cal ka BP),温度有所回升,但存在一定的冷暖波动;阶段Ⅲ(8.6～6.7cal ka BP),气候仍相对偏凉,且比较干燥;阶段Ⅳ(6.7～5.8cal ka BP),气候开始转温;阶段Ⅴ(5.8～2.9cal ka BP),气候温暖偏湿,为全新世气候最适宜期;阶段Ⅵ(2.9～0.2cal ka BP),气候趋于凉干,湖水也越来越浅,最终在0.2cal ka BP前后干涸消失。     

河西走廊花海古湖泊早、中全新世湖水盐度变化及其环境意义

通过对花海古湖泊沉积剖面8.42~0.405 m沉积物样品的矿物和化学元素测定,分析了沉积物中盐类矿物含量及化学元素K/Na比值的变化情况,结合已有的年代地层结果,重建了花海古湖泊10.47~5.5 cal ka BP湖水盐度变化. 结果表明：花海湖泊全新世湖相沉积阶段中,除个别层位以硫酸盐类矿物沉积为主外,早全新世(10.47~8.87 cal ka BP)和中全新世(8.87~5.5 cal ka BP)均以碳酸盐盐类矿物沉积为主,并且早全新世时期K/Na高于中全新世时期,揭示了早全新世时期湖水盐度高于中全新世时期. 这一结果与该湖泊沉积过程所揭示的湖泊水位变化、粒度等揭示的有效湿度变化具有一致性,表明花海湖泊早、中全新世湖水盐度的高低可以指示其湖泊水位的变化,并间接反映了有效湿度的变化. 结合花海湖泊晚全新世湖泊萎缩、气候干旱的特点,该区域早、中、晚全新世气候干湿变化变化模式可以概况为早全新世降水增强、气候呈现由干向湿的转变,中全新世有效湿度最大,晚全新世气候干旱. 这种全新世气候干湿变化模式有别于西风区,亦与季风区不完全相同,呈现出了一种季风-西风过渡带全新世气候干湿变化的模式.     

青藏高原东北部共和盆地风成沉积地球化学特征及其揭示的气候变化

通过对共和盆地东部风成沉积的地球化学分析,并结合14C和OSL年代,重建了区域末次盛冰期以来气候变化过程。21 ka BP之前气候寒冷偏湿,21～15.82 ka BP为末次盛冰期(LastGlacial Maximum,LGM),气候极为寒冷干燥;15.82～9.5 ka BP气候转暖且偏干,其中14.5～13.6ka BP和11.9～9.5 ka BP气候明显冷干,分别为老仙女木时期(Oldest Dryas,OD)和新仙女木时期(Younger Dryas,YD),而15.82～14.5 ka BP和13.6～11.9 ka BP(BФlling-AllerФd暖期,B/A)相对温暖;9.5～7.2 ka BP暖湿程度明显提高,7.2～5.1 ka BP气候波动频繁,相对冷干和相对暖湿多次更替。5.1～2.7 ka BP暖湿程度基本稳定,之后气候趋于寒冷但湿度明显较大。这些气候变化过程与青藏高原大量的古气候信息记录具有良好的一致性,表明共和盆地气候变化与青藏高原气候变化的高度一致性。     

The terrestrial fauna of the Late Triassic Pant-y-ffynnon Quarry fissures,South Wales,UK and a new species of Clevosaurus (Lepidosauria: Rhynchocephalia)

Pant-y-ffynnon Quarry in South Wales yielded a rich cache of fossils in the early 1950s, including articulated specimens of new species (the small sauropodomorph dinosaur Pantydraco caducus and the crocodylomorph Terrestrisuchus gracilis), but no substantial study of the wider fauna of the Pant-y-ffynnon fissure systems has been published. Here, our overview of existing specimens, a few described but mostly undescribed, as well as freshly processed material, provides a comprehensive picture of the Pant-y-ffynnon palaeo-island of the Late Triassic. This was an island with a relatively impoverished fauna dominated by small clevosaurs (rhynchocephalians), including a new species, Clevosaurus cambrica, described here from a partially articulated specimen and isolated bones. The new species has a dental morphology that is intermediate between the Late Triassic Clevosaurus hudsoni, from Cromhall Quarry to the east, and the younger C. convallis from Pant Quarry to the west, suggesting adaptive radiation of clevosaurs in the palaeo-archipelago. The larger reptiles on the palaeo-island do not exceed 1.5?m in length, including a small carnivorous crocodylomorph, Terrestrisuchus, and a possible example of insular dwarfism in the basal dinosaur Pantydraco.     

Définition d'une limite multicritère ; stratigraphie du passage Campanien–Maastrichtien du site géologique de Tercis (Landes,SW France)Definition of a multi-criteria boundary; stratigraphy of the Campanian–Maastrichtian interval of the geological site at Tercis (Landes,SW France)

Lithostratigraphy, physicochemical stratigraphy, biostratigraphy, and geochronology of the 77–70 Ma old series bracketing the Campanian–Maastrichtian boundary have been investigated by 70 experts. For the first time, direct relationships between macro- and microfossils have been established, as well as direct and indirect relationships between chemo-physical and biostratigraphical tools. A combination of criteria for selecting the boundary level, duration estimates, uncertainties on durations and on the location of biohorizons have been considered; new chronostratigraphic units are proposed. The geological site at Tercis is accepted by the Commission on Stratigraphy as the international reference for the stratigraphy of the studied interval. To cite this article: G.S. Odin, C. R. Geoscience 334 (2002) 409–414.     

The effect of water on accessory phase solubility in subaluminous and peralkaline granitic melts

The solubilities of columbite, tantalite, wolframite, rutile, zircon and hafnon were determined as a function of the water contents in peralkaline and subaluminous granite melts. All experiments were conducted at 1035 °C and 2 kbar and the water contents of the melts ranged from nominally dry to approximately 6 wt.% H₂O. Accessory phase solubilities are not affected by the water content of the peralkaline melt. By contrast, solubilities are affected by the water content of the subaluminous melt, where the solubilities of all the accessory phases examined increase with the water content of the melt, up to 2 wt.% H₂O. At higher water contents, solubilities are nearly constant. It can be concluded that water is not an important control of accessory phase solubility, although the water content will affect diffusivities of components in the melt, thus whether or not accessory phases will be present as restite material. The solubility behaviour in the subaluminous and peralkaline melts supports previous spectroscopic studies, which have observed differences in the coordination of high field strength elements in dry vs. wet subaluminous granitic glasses, but not for peralkaline granitic glasses. Lastly, the fact that wolframite solubility increases with increasing water content in the subaluminous melt suggests that tungsten dissolved as a hexavalent species.     

Quaternary stresses revealed by calcite twinning inversion: insights from observations in the Savonnières underground quarry (eastern France)

Calcite samples were extracted both from the rock matrix and the superficial coating of a karstified fault plane of an underground quarry, located in the eastern border of the Paris basin. The karstification is dated as Quaternary. Analysis of mechanical calcite twinning reveals that only the calcite matrix has also undergone a compression trending WNW that can be attributed to the Mio-Pliocene alpine collision. Both coating and matrix have undergone a strike-slip regime with σ₁ roughly trending north–south, that could correspond to the regional present-day state of stress, a strike-slip compression rather trending NNW, modified by local phenomena. To cite this article: M. Rocher et al., C. R. Geoscience 335 (2003).     

HYDROGEOLOGY

正20141756 Chen Ruige(Mathematical College,China University of Geosciences,Beijing100083,China);Zhou Xun Numerical Simulation of Groundwater Level Fluctuation in a Coastal Confined Aquifer with Sloping Initial Groundwater Level Induced by the Tide(Geological Bulletin of China,ISSN1671-2552,CN11-4648/P,32(7),2013,p.1099-1104,6 illus.,16 refs.) Key words:confined water,groundwater level     

METAMORPHIC PETROLOGY

正20141408 Cai Jia(Institute of Geology,Chinese Academy of Geological Sciences,Beijing100037,China);Liu Fulai Petrogenesis and Metamorphic P-T Conditions of Garnet-Spinel-Biotitebearing Paragneiss in Danangou Area,Daqingshan-Wulashan Metamorphic Complex Belt(Acta Petrologica Sinica,ISSN1000-0569,CN11-1922/P,29(7),     

SERIALS

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GEOPHYSICAL EXPLORATION

正20142386An Guoying(China Aero Geophysical Survey and Remote Sensing Center for Land and Resources,Beijing 100083,China)Application of Satellite Remote Sensing in Regional Hydrogeological Investigation:Taking Cenozoic Strata in Wenquan Sheet(1∶250 000)of Karakoram Range as an Example(Geosci-     

QUATERNARY GEOLOGY & GEOMORPHOLOGY

正20141016An Chengbang(Key Laboratory of Western China’s Environmental Systems,Ministry of Education,Lanzhou University,Lanzhou 730000,China);Zhao Yongtao Lake Records during the Last Glacial Maximum from Xinjiang,NW China and Their Climatic Impli-     

PETROLEUM GEOLOGY

正20141538 Cao Qing(School of Earth Sciences and Engineering,Xi’an Petroleum University,Xi’an 710065,China);Zhao Jingzhou Characteristics and Significance of Fluid Inclusions from Majiagou Formation,Yichuan Huangling Area,Ordos Basin(Advances in Earth Science,ISSN1001-8166,CN62-1091/P,28(7),2013,p.819-828,7 illus.,3 tables,43 refs.)