西藏纳木错晚更新世以来湖面变化和藏北高原古大湖的演化

根据西藏纳木错及邻区发现的多处湖岸阶地和高位湖相沉积,确定了藏北高原古大湖的存在.水准测量表明,在纳木错沿岸发育了6级湖岸阶地,以及拔湖48～139.2m的高位湖相沉积;在拔湖26m以下,发育有8～30条湖岸堤;一条明显的湖蚀凹槽则集中出现在拔湖17.5～19.8m的高度上,与纳木错和仁错的分水垭口的高度相当.纳木错沿岸和邻区湖相或湖滨相沉积物的铀系年龄测定表明,高位湖相沉积形成于115.9～71.8 kaB.P.的晚更新世早期;第6至第2级阶地形成于53.7～28.2 kaB.P的晚更新世中晚期;与湖蚀凹槽相当的湖滨相沉积则稍早于29.3 kaB.P.;第2至第1级阶地,14C测定结果为2350～10390 aB.P..     

西藏纳木错晚更新世以来湖面变化和藏北高原古大湖的演化

根据西藏纳木错及邻区发现的多处湖岸阶地和高位湖相沉积,确定了藏北高原古大湖的存在。水准测量表明,在纳木错沿岸发育了6级湖岸阶地,以及拔湖48～139.2m的高位湖相沉积;在拔湖26m以下,发育有8～30条湖岸堤;一条明显的湖蚀凹槽则集中出现在拔湖17.5～19.8m的高度上,与纳木错和仁错的分水垭口的高度相当。纳木错沿岸和邻区湖相或湖滨相沉积物的铀系年龄测定表明,高位湖相沉积形成于115.9～71.8kaB.P.的晚更新世早期;第6至第2级阶地形成于53.7～28.2kaB.P.的晚更新世中晚期;与湖蚀凹槽相当的湖滨相沉积则稍早于29.3kaB.P.;第2至第1级阶地,14C测定结果为2350～10390aB.P.。     

西藏纳木错晚更新世以来湖面变化和藏北高原古大湖的演化

根据西藏纳木错及邻区发现的多处湖岸阶地和高位湖相沉积,确定了藏北高原古大湖的存在。水准测量表明,在纳木错沿岸发育了6级湖岸阶地,以及拔湖48～139．2m的高位湖相沉积;在拔湖26m以下,发育有8～30条湖岸堤;一条明显的湖蚀凹槽则集中出现在拔湖17．5～19．8m的高度上,与纳木错和仁错的分水垭口的高度相当。纳木错沿岸和邻区湖相或湖滨相沉积物的铀系年龄测定表明,高位湖相沉积形成于115．9～71．8kaB．P．的晚更新世早期;第6至第2级阶地形成于53．7～28．2kaB．P．的晚更新世中晚期;与湖蚀凹槽相当的湖滨相沉积则稍早于293kaB．P．;第2至第1级阶地,^14C测定结果为2350-10390aB．P．。     

西藏纳木错末次盛冰期以来的古植被、古气候和湖面变化

西藏纳木错湖相沉积的U系、14C年龄和孢粉分析结果表明,纳木错沿岸的拔湖约1.5～8.3m和8.3～15.6m的T1和T2分别形成于末次盛冰期以来约(11.81±0.10)～(4.22±0.09)kaB.P.期间和(28.2±2.8)kaB.P.左右。该套湖相层的孢粉组合、地层和湖岸堤的分布表明,在末次盛冰期期间,纳木错湖面主要波动于拔湖12～20m之间,但湖面最低可达拔湖约8m。区域植被主要为以蒿和莎草科为主、含松和桦的草原。在约11.8～4.2kaB.P.期间,湖面波动于拔湖2～9m之间,区域气候整体较为暖湿。其中全新世大暖期出现在约8.4～4.2kaB.P.期间,气候温暖湿润,区域出现针叶林或针阔叶混交林,气温可能比现今高约5℃,降水量可能比现今多100～200mm,湖面扩张并升高,最高可达拔湖约10m。     

西藏纳木错末次盛冰期以来的古植被、古气候和湖面变化

西藏纳木错湖相沉积的U系、14C年龄和孢粉分析结果表明,纳木错沿岸的拔湖约1.5～8.3m和8.3～15.6m的T1和T2分别形成于末次盛冰期以来约(11.81±0.10)～(4.22±0.09)kaB.P.期间和(28.2±2.8)kaB.P.左右.该套湖相层的孢粉组合、地层和湖岸堤的分布表明,在末次盛冰期期间,纳木错湖面主要波动于拔湖12～20 m之间,但湖面最低可达拔湖约8m.区域植被主要为以蒿和莎草科为主、含松和桦的草原.在约11.8～4.2ka B.P.期间,湖面波动于拔湖2～9m之间,区域气候整体较为暖湿.其中全新世大暖期出现在约8.4～4.2 ka B.P.期间,气候温暖湿润,区域出现针叶林或针阔叶混交林,气温可能比现今高约5℃,降水量可能比现今多100～200mm,湖面扩张并升高,最高可达拔湖约10m.     

西藏纳木错盆地116ka以来沉积演化与青藏高原隆升

根据湖相或湖滨相沉积的铀系等时线年龄测定结果,116kaB.P.以来,在西藏纳木错沿岸,发育了拔湖48m以下的6级湖岸阶地和拔湖48m以上,最高至139.2m的高位湖相沉积.可划分出3个沉积相组合,其演化可划分为4个阶段:①116~72kaB.P.,为深湖环境,古湖面拔湖高于现今纳木错140~48m;②72~37kaB.P.,为半深湖环境,拔湖为48~26m;③37~30kaB.P.,为浅湖环境,拔湖26~19m;④30kaB.P.以来,湖水逐渐变浅,拔湖<19m.纳木错盆地沉积与青藏高原隆升响应关系,揭示出高原自116kaB.P.以来先后经历了稳定期、持续逐步较快隆升期(116~37kaB.P.)、急剧强烈阶段性隆升期(37~30kaB.P.)和较稳定期(30kaB.P.以来).青藏高原的隆升是一个多阶段、不等速和非均变的复杂过程.      

西藏纳木错晚更新世以来湖面变化和湖相沉积中粘土矿物显示的环境信息

通过对西藏海拔最高、面积最大湖泊-纳木错周缘湖相沉积、湖岸堤的野外调查和湖岸阶地的水准测量,发现在纳木错沿岸拔湖48m以下,发育有6级湖岸阶地,拔湖48~139.2m发育有高位湖相沉积。湖相沉积物的同位素测年结果表明,纳木错湖泊发育与藏北高原东南部古大湖演化可划分为3个阶段:①116~37kaB.P.间的古大湖期;②37~30kaB.P.间的外流湖期;③30kaB.P.以来的纳木错期。根据纳木错晚更新世以来湖相沉积中粘土矿物的X光衍射分析结果,以及采用比值法、高岭石法和衍射峰法的研究,探讨了粘土矿物所显示的环境变化信息。粘土矿物成分变化表明,该区已具备了寒温带干旱、半干旱区的气候环境特征。为研究青藏高原的湖泊演化、气候变化、古地理变迁及其隆升过程等提供了新资料。      

纳木错湖相沉积与藏北高原古大湖

藏北高原古湖岸线分布广泛，湖相沉积与湖成地貌发育，目前，在纳木错沿岸可清晰地划分出4-6级湖岸阶地，最高湖相沉积高出现代湖面150m，沿岸堤可多达50条，雄曲-那曲谷地是连接纳木错盆地与其以西的仁错-久如错盆地的分水谷地，也是构成纳木错2湖岸阶地顶部的第四纪湖相沉积，构成宽谷的谷底，从最高湖岸线的分布与湖相沉积物、湖成地貌等标志综合判定，古大湖泊的面积要比现代湖泊面积大数十倍，末次古大湖的时代发生于末次冰期间冰段。     

西藏纳木错第四纪湖相地层划分及纳木错群的建立

第四纪湖相地层剖面实测和水准仪测量表明,在西藏纳木错沿岸,发育有拔湖48m以下的6级湖岸阶地和拔湖48m以上最高至139.2m的高位湖相沉积。纳木错湖相或湖滨相沉积的铀系等时线年龄测定结果表明,高位湖相沉积形成于晚更新世早期,第六至第三级阶地则分别形成于晚更新世中期至晚期。14C法测年表明,第二和第一级阶地的形成时间介于13820～2350年间,属全新世。根据沉积相、岩相组合等特征,并结合同位素测年、微体古生物鉴定等资料,将该套地层命名为纳木错群,由上更新统干玛弄组和全新统扎弄淌组组成。     

西藏纳木错第四纪湖泊沉积的初步观察——兼论纳木错与仁错—久如错连通和藏北高原古大湖问题

藏北高原古湖岸线分布广泛,湖泊沉积与湖成地貌发育。目前,在纳木错沿岸不仅发现了由水平层理十分发育的砂与粘土所组成的、高出湖面分别为3～12m、15～22m、25～30m与35～45m的4级湖岸阶地,以及覆于基岩之上、高出湖面60～150m的湖相沉积和多达50条左右、由扁圆的湖滨相砾石所组成的湖岸堤。而且在连结纳木错与其西北的仁错约玛、仁错贡玛、久如错的分水岭宽谷底部(分别高     

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.     

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.)     

GEOCHEMISTRY

正20142002 Wei Hualing(Institute of Geophysical and Geochemical Exploration,Chinese Academy of Geological Sciences,Langfang065000,China);Zhou Guohua Element Content and Mineral Compositions in Different Sizes of Soil in Tongling Area,Anhui Province(Geological Bulletin of China,ISSN1671-2552,CN11-4648/P,32(11),2013,p.1861     

ENGINEERING GEOLOGY

正20141768 An Shaopeng(Institute of Rock and Soil Mechannics,Chinese Academy of Sciences,Wuhan 430071,China);Wei Lide Experimental Study on Mechanical Behavior of Xigeda Formation Siltstone and Structure Interface(Journal of Engineering Geology,ISSN1004-9665,CN11-3249/P,21(5),2013,p.702-708,9illus.,1 table,16 refs.)