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1.
DANIEL VERES SIWAN M. DAVIES BARBARA WOHLFARTH FRANK PREUSSER STEFAN WASTEGÅRD LINDA AMPEL ANNE HORMES GÖRAN POSSNERT JEAN-PAUL RAYNAL GÉRARD VERNET 《Boreas: An International Journal of Quaternary Research》2008,37(3):434-443
A new tephra has been identified within a long core (EC 3) sequence recovered from Les Echets, near Lyon, France. This visible tephra was discovered as part of a high resolution multiproxy re-investigation of the Les Echets sequence. Independent chronological information suggests that the tephra is c . 2 000–45 000 years old, and geochemical analysis indicates that it is of basanitic composition. The latter suggests a possible origin in the Eifel; however, as yet, no other volcanic events or deposits can be correlated to the Les Echets tephra. New sedimentological and chronological data are presented indicating that the tephra falls within an interval that most likely correlates with Dansgaard–Oeschger events 12-9. Thus, this tephra could potentially be an important middle MIS 3 marker horizon in central Europe if it can be traced in other palaeorecords. 相似文献
2.
以南海北、西、南部3个沉积速率相对较高而且连续的沉积柱状样MD2904,MD2901和MD2897为基础,通过粒度、碳酸盐、有机地球化学和元素分析,并综合前人研究成果,对南海MIS3期进行探讨。结果显示,南海MIS3是末次冰期中的弱暖期,海水表层古温度比相邻的MIS2和MIS4期略高,但是明显比MIS1和MIS5期低。MIS3的最大特点就在于其气候的不稳定性,发生了多次气候快速变化事件。在格陵兰冰芯中记录的千年尺度快速气候变化事件（D/O事件和Heinrich事件）基本上在南海北、西、南部都有响应,具有与全球同步的特征。南海MIS3古生产力都显示出较高的特点,这与东亚季风有着密切的关系,北部主要受冬季风影响,西部和南部主要受夏季风影响。南海南部MIS3表现出比MIS5更高的古生产力和更强的夏季风强度,这一特点有待更进一步深入研究。 相似文献
3.
DANIEL VERES BARBARA WOHLFARTH VALÉRIE ANDRIEU-PONEL SVANTE BJÖRCK JACQUES-LOUIS DE BEAULIEU GUNNAR DIGERFELDT PHILIPPE PONEL LINDA AMPEL SIWAN DAVIES EMMANUEL GANDOUIN SOUMAYA BELMECHERI 《Boreas: An International Journal of Quaternary Research》2007,36(3):326-340
Two new long sediment cores (EC1 and EC3), recovered from different locations within the infilled basin at Les Echets, France, provide a new high-resolution record of terrestrial and lacustrine responses to climatic changes during Marine Isotope Stages (MIS) 3 and 2. The lithologies of the cores are described in detail and correlated with each other by stratigraphic marker horizons, fluctuations in organic matter and AMS radiocarbon ages. The tentative correlation of the new cores to those described and analysed by de Beaulieu et al. (1980) and de Beaulieu & Reille (1984a) provides a preliminary chronostratigraphic framework. Sedimentation during MIS3 started with accumulation of sands and silts and was followed by alternating gyttja and clayey gyttja silts. Exceptionally high sedimentation rates during MIS2 led to the infilling of the basin. Alternating organic-rich and minerogenic-rich sediments appear to coincide with changes in pollen assemblages (de Beaulieu & Reille 1984a) and suggest that millennial-scale climatic changes controlled lake productivity and catchment stability during most of MIS3. 相似文献
4.
María Fernanda Snchez Goi Jean-Louis Turon Frdrique Eynaud Sandra Gendreau 《Quaternary Research》2000,54(3):394
Pollen, foraminifer, dinocyst, and coarse lithic high-resolution analyses and δ18O measurements have been carried out for the last-glacial section of marine core MD95-2042 located near the southwestern margin of the Iberian Peninsula. The pollen data indicate a high frequency of vegetational changes on the adjacent continent during this period, suggesting a climatic variability very similar to that of the Dansgaard-Oeschger cycles recorded by the Greenland ice cores. The detailed direct correlation of the terrestrial and marine proxy data from core MD95-2042 indicates a three-phase pattern of Heinrich events in land and ocean environments. The first and last phases of the H5 and H4 events are characterized by a mild and humid climate in southwestern Europe, probably associated with the European origin of the ice-rafted detritus. The middle phase exhibits a cold and dry climate in Iberia linked with the maximum input of ice-rafted detritus. This phase seems to correspond with the Laurentide ice-sheet surges. Between the Heinrich events, several cold and dry periods on land are correlated with stades of the Dansgaard-Oeschger cycles. The impact of the Dansgaard-Oeschger stades in southwestern Europe seems to be preferentially connected to the cold winter air masses reaching this mid-latitude region. 相似文献
5.
Orbital- and sub-orbital-scale climate impacts on vegetation of the western Mediterranean basin over the last 48,000 yr 总被引：1，自引：0，他引：1
High-resolution pollen analysis of Alborán Sea core MD95-2043 provides a 48-ka continuous vegetation record that can be directly correlated with sea surface and deep-water changes. The reliability of this record is supported by comparison with that of Padul (Sierra Nevada, Spain). Marine Isotope Stage (MIS) 3 was characterised by fluctuations in Quercus forest cover in response to Dansgaard-Oeschger climate variability. MIS 2 was characterised by the dominance of semi-desert vegetation. Despite overall dry and cold conditions during MIS 2, Heinrich events (HEs) 2 and 1 were distinguished from the last glacial maximum by more intensely arid conditions. Taxon-specific vegetation responses to a tripartite climatic structure within the HEs are observed. In MIS 1, the Bölling-Allerød was marked by rapid afforestation, while a re-expansion of semi-desert environments occurred during the Younger Dryas. The maximum development of mixed Quercus forest occurred between 11.7 and 5.4 cal ka BP, with forest decline since 5.4 cal ka BP. On orbital timescales, a long-term expansion of semi-desert vegetation from MIS 3 into MIS 2 reflects global ice-volume trends, while Holocene arboreal decline reflects summer insolation decrease. The influence of precession on the amplitude of forest development and vegetation composition is also detected. 相似文献
6.
Luis Gómez‐Orellana Pablo Ramil‐Rego Castor Muñoz Sobrino 《Boreas: An International Journal of Quaternary Research》2013,42(3):729-744
This paper describes and discusses the palaeobotanical data obtained from organic levels of two exposed deposits on the Atlantic shore of the northwestern Iberian Peninsula. Radiocarbon dating assigns these levels to a period of marine regression at the end of MIS 3 and the beginning of the Last Glacial Maximum. The pollen record shows an initial predominance of tree taxa (mainly deciduous, including the presence of Fagus far from its current limit), followed by an episode of partial forest retraction related to the end of MIS 3 and the beginning of the Last Glacial Maximum. However, the presence of numerous tree taxa in the record, even during the cold intervals associated with Heinrich events, points to the existence of sheltered refugia for these species during this period, in keeping with the conclusions of recent reviews of the vegetation dynamics of this region for the Lateglacial and the Holocene. 相似文献
7.
ABSTRACT This paper presents new geochemical data on gas-hydrate-bearing mud volcanoes discovered for the first time in the Gulf of Cadiz during cruises TTR9 and TTR10 of the R/V Professor Logachev in 1999–2000. The estimated gas hydrate content is 3–16% of sediment volume and 5–31% of pore space volume. Estimated values of the water isotopic composition for the Ginsburg mud volcano are very heavy for δ18 O (up to +53‰) and light for δD (up to − 210‰). Gas released from the hydrates contains 81% of C1 and 19% of C2+ . The inferred source of the gas in the hydrates is enriched in C2 –C6 (≤ 5%), indicating that the gas has a thermogenic origin. Gas hydrate of cubic structure II should be formed from a gas of such composition. It is interpreted that the composition of the mud volcano fluid corresponds to deep oil basins below the Gulf of Cadiz. 相似文献
8.
南海具有典型边缘海特征,其北部陆坡由于具有高沉积速率的地层剖面,可以用于研究亚轨道尺度气候变化。本研究以南海北部陆坡下部MD12 3432柱状样(19°16.88′N,116°14.52′E,水深2 125 m)为主要研究材料,分析其粗组分百分含量、底栖有孔虫丰度和特定环境指示属种的百分含量与丰度,并结合相关研究结果,运用多指标综合分析,重建了南海北部陆坡MIS 11期(距今约40万年)以来的表层初级生产力和底层水溶解氧含量的演化情况。与之前研究不同,本研究发现MIS11期以来南海北部的古生产力在温暖的间冰期高、在寒冷的冰期低,且主要受控于东亚夏季风影响下低纬地区降水强度的变化。在MIS 7期和MIS 9期可能有较高溶解氧含量的底层水进入南海北部,导致在高生产力的暖期中,喜氧的低生产力指示种Cibicidoides wuellerstorfi丰度增加。 相似文献
9.
A comparative analysis of two sediment cores from perialpine lakes (L. Zürich and L. Geneva) helped to clarify pathways of sulphur fixation in freshwater sediments. Despite greater than three-fold differences in lake water sulphate concentration equal amounts of sulphur are fixed in the sediments. The maximum sedimentary sulphur concentrations attain 1% (dry weight) which is similar to the sulphur content of modem, near-shore marine sediments. This is also expressed in low C org /Stot ratios which range from 2.5–8.
An analysis of the sulphur pools showed that organic sulphur compounds are the main components of the sedimentary sulphur, accounting for ˜ 80% and ˜ 60% of the total sulphur in Lakes Zürich and Geneva, respectively. The largest single sulphur pool is the sulphate-esters, which comprise 40–60% of the total sedimentary sulphur. Substantial amounts of the organic sulphur compounds must be formed within the sediment by boundary-layer microbial communities at the oxic-anoxic transition zone. This possibly suggests rapid recycling of sulphur in suboxic zones. Because of low concentration of SO2 4 -- in the watermass, the zone of sulphate reduction is very thin. This coupled with the mobility of some sulphide oxidizing microbial colonies (e.g. Beggiutoa ) potentially results in an almost complete recycling of the sulphur pool near the sediment-water interface. Reduced sulphur caught in this cycling process is unavailable for sedimentary pyrite formation. The Corg /Spyrite ratios for these sediments are thus high. If organically bound sulphur is not completely transformed into pyrite during late diagenesis, the Corg / Spyrite ratio can serve as a sensitive indicator for the salinities of anaent depositional environments. 相似文献
An analysis of the sulphur pools showed that organic sulphur compounds are the main components of the sedimentary sulphur, accounting for ˜ 80% and ˜ 60% of the total sulphur in Lakes Zürich and Geneva, respectively. The largest single sulphur pool is the sulphate-esters, which comprise 40–60% of the total sedimentary sulphur. Substantial amounts of the organic sulphur compounds must be formed within the sediment by boundary-layer microbial communities at the oxic-anoxic transition zone. This possibly suggests rapid recycling of sulphur in suboxic zones. Because of low concentration of SO
10.
Shrimp U–Pb zircon dating of structurally constrained felsic orthogneiss samples in the western Musgrave Block has been used to delineate discrete magmatic and metamorphic events at c . 1300 and c . 1200 Ma. The dating of pre-D1 and post-D1 felsic orthogneiss constrains D1 to have occurred at 1312±16 to 1324±4 Ma. This is the first geochronological study to identify such a metamorphic and deformation event in the Musgrave Block. D1 was accompanied by a major magmatic event involving the emplacement of voluminous felsic orthogneiss between 1296 and 1324 Ma. Zircon overgrowths on numerous igneous zircon cores give a consistent age of c . 1200 Ma, reflecting zircon growth during a second high-grade metamorphic event (D2 ). This c . 1200 Ma metamorphic event was followed by the intrusion of a c . 1190 Ma megacrystic granite. The c . 1300 and c . 1200 Ma events in the Musgrave Block can be tentatively correlated with metamorphic events in the Albany-Fraser Orogen, and the Windmill Islands and Bunger Hills in east Antarctica. A major continuous Grenville-age orogenic belt joining these areas may have represented a plate boundary between the pre-Rodinian proto-Australian continent and proto-Antarctica during the formation of Rodinia in the Mesoproterozoic. 相似文献
11.
银川盆地位于东亚季风与西风带的交界带,地层沉积物记录着气候环境的演变信息。通过对银川盆地LS01钻孔沉积物进行光释光定年、粒度分析以及端元分析重建了该地区MIS6—MIS5时期的气候演变序列。结果表明,端元分析得到4个有具体环境指示意义的端元Em1—Em4:Em1代表了水动力较弱的弱流水或湖沼相沉积;Em2代表了水动力较强的河流沉积;Em3和Em4可指代区域构造抬升事件。气候演变分为6个阶段:150~137 ka(MIS6),银川盆地气候冷干,出现两次构造抬升事件;137~110 ka(MIS5),气候整体较为暖湿,期间有3次暖事件a1(137~129 ka)、a2(124~120 ka)和a3(118~111 ka);110~107 ka(MIS5),气候转向冷干;107~102 ka(MIS5),气候由冷转暖,出现冷事件b1(106~104 ka),整体偏暖湿;102~87 ka(MIS5),气候较冷干;87~75 ka(MIS5),出现冷事件b2(87~84 ka),但整体偏暖湿。该区域MIS6—MIS5阶段气候变化主要受夏季太阳辐射和岁差驱动。 相似文献
12.
南海北部海水物理化学性质不但受东亚季风的影响,还受到珠江陆源输入的影响。文章根据对南海北部ODP 1144站浮游有孔虫属种组合变化和氧同位素分析,以及浮游有孔虫表层海水温度转换函数的研究结果表明:南海北部MIS 3期的表层海水温度在H2~H6事件时明显降低,并在H4~H5(45.66~38.77kaB.P.) 期间,表层海水冬季温度变化频繁,且幅度较大。35~29kaB.P. ,浮游有孔虫暖水种含量减少,浮游有孔虫氧同位素值增重,同时高生产力属种Neogloboquadrina dutertrei的含量增加,说明冬季风在该阶段强化。此外,52~46kaB.P.期间,N.dutertrei含量增加,浮游有孔虫氧同位素较低,表层海水温度没有明显的变化,所以此时南海北部的高生产力可能与珠江陆源输入的增加有关,指示东亚夏季风的加强。 相似文献
13.
通过对祁连山南坡木里地区晚更新世地层剖面AMS14C年代的测定,以及对沉积物粒度、磁化率及SiO2、Al2O3、Fe2O3等氧化物含量的研究,重建了研究区晚更新世晚期44.8～35ka B.P.的气候变迁。木里地区晚更新世晚期44.8～35ka B.P.的气候可以分为3个阶段:(1)44.8～40.5ka B.P.,气候温暖湿润,41.9ka B.P.出现的暖事件与D-O振荡中的IS12对应;(2)40.5～35.5ka B.P.,气候波动频繁且在波动中变冷,该阶段成功捕捉到3次D-O振荡中的暖事件和1次Heinrich冷事件,3次暖事件与D-O振荡中的IS9、IS10、IS11对应,时间分别为35.8ka B.P.、37.5ka B.P.、39.7ka B.P.,冷事件与D-O振荡中的H3对应,时间为35.5ka B.P.;(3)35.5～35ka B.P.,气候波动大,具变暖趋势。整个阶段的气候波动与深海氧同位素第3阶段后期气候变化特征较吻合,亦揭示了全球变化信号在研究区的响应特征。 相似文献
14.
青藏高原东缘都江堰湖相沉积MIS3a阶段的快速气候变化记录 总被引：2，自引：0，他引：2
深海氧同位素第3阶段晚期(MIS3a)是青藏高原较为特殊的暖湿时期, 为了解这一时期高原东缘的气候变化细节, 利用AMS14C定年和粒度、总有机碳、正构烷烃等环境代用指标提取了四川都江堰湖相沉积剖面的相应记录.经过校正后的日历年龄显示此剖面沉积于43.6~34.6 kaBP期间, 记录了千年尺度的D-O旋回事件, 其分布时段分别为: DO11(43.6~41.8 kaBP), DO10(41.8~39.2 kaBP), DO9(39.2~37.7 kaBP), DO8(37.7~35.5 kaBP), DO7(35.5 kaBP~未见顶).该剖面总有机碳曲线与南京葫芦洞石笋和格陵兰冰心(GRIP)氧同位素曲线的对比表明, 该区域气候记录对全球高纬地区的冰量变化和亚洲季风演化具有响应; 而中纬度太阳辐射岁差对该区域气候波动的控制作用较强导致了细节上存在差异. 相似文献
15.
Major and trace element distribution in the bottom sediments from Hole 13 drilled in Lake Grand, Magadan district, was studied using the method of principal components. It was established that geochemical characteristics are correlated with environmental changes. The sediments of cold MIS2 and MIS4 are characterized by the enriched TiO2, MgO, Al2O3, Fe2O3, and Cr and low Na2O, K2O contents, which is related to the grain-size composition of sediments. Sediments of warm stages show an opposite tendency. High concentration peaks of iron, phosphorus, and manganese correspond to the accumulation levels of vivianite and ferromanganese rocks. Silica is represented by biogenic and abiogenic varieties. Maximum SiO2 contents were found in the Late Holocene sediments and mark the high biological productivity of the basin. Revealed variations of some elements are correlated with the Heinrich events. 相似文献
16.
通过对云南泸沽湖高分辨率沉积指标序列(硅藻、枝角类和孢粉)的对比分析,初步揭示了水生生物(硅藻、枝角类和水生孢粉)对末次冰盛期期间气候变化的快速响应过程.结果表明,硅藻群落组成首先响应末次冰盛期时期的开始变冷,枝角类滞后,水生孢粉则表现为渐进的响应过程.然而,泸沽湖沉积硅藻记录对末次冰期以来的短时间尺度气候快速变化的Heinrich和新仙女木事件并未有响应,揭示气候事件判别的准确性取决于指标直接响应气候的特征以及多指标的综合对比.综合西南季风区云南不同海拔湖泊沉积记录(硅藻、孢粉、摇蚊等)获得的2万年以来数据及序列表明,末次冰期千年尺度的气候突变事件( Heinrich 1、 B?lling/Aller?d暖期和新仙女木YD冷事件)在整个西南季风系统中都有反映,且气候事件变化区间及幅度存在区域差异,其根本原因是受不同气候系统、复杂地形(青藏高原)的制约. 相似文献
17.
Ji-Ling Song Hong-Yan Sun Ming-Zhong Tian Xu-Jiao Zhang Xue-Feng Wen Miao Sun 《地学前缘(英文版)》2018,9(2):431-439
We describe the last glaciation climatic history Marine Isotope Stage(MIS, 2-4) from 66.7 ka to 14.5 ka in Hexigten, northeast Inner Mongolia, North China. The climate of the region experienced frequent and significant fluctuations between dry-cold and less dry-cold during the late MIS4. The climate was generally warm and humid during early MIS3(MIS3 c) and late MIS3(MIS3 a), whereas it was cold and dry in middle MIS3(MIS3 b) and during MIS2. In this study, the cold and dry conditions were correlated with a stronger East Asian winter monsoon and strong dune activity; whereas, warm and humid conditions were related to a stronger East Asian summer monsoon(EASM) and weak dune activity. This study establishes six distinct dry and cold intervals during the last glacial period(66.7-14.5 ka) based on optically stimulated luminescence data, multi-proxies record(magnetic susceptibility, grain size analysis, Rb/Sr, SiO2/TiO2) and chemical index of alteration(CIA). The last glacial period may be correlated with Heinrich events 1 to 6 which were further confirmed by comparison with the Hulu cave stalagmites and Greenland ice core records. It is concluded that the study area was substantially affected by the EASM, as compared with the loess-desert transition zone of the Chinese Loess Plateau, especially in MIS3 c and suggested that the East Asian monsoon played a pivotal role in the last glacial period climate and dune activity. 相似文献
18.
The dominant foliation (S2) in the metapelites of the Southalpine basement, near the western side of the Tertiary Adamello intrusive stock, is a Variscan greenschist facies planar fabric, slightly reworked during thick-skin Alpine tectonics. S2 is defined by muscovite and chlorite and was formed by decrenulation of pre-existing foliations, which are confined to metre-size, less-deformed domains and defined by biotite and white mica. The pre-S2 fabric is composite (D1a & D1b) and defined by contrasting amphibolite facies metamorphic assemblages in different residual sites. Cld+BtI +Grt+MsI +Pl+Qtz and St+BtII +Grt+MsII +Pl+Qtz assemblages mark D1a and D1b fabrics respectively; these developed during successive steps of a single, temperature-prograde polyphase event, rather than during separate tectonometamorphic imprints affecting different tectonic units, later coupled during a D2 greenschist facies stage. Thermobarometric estimates of assemblages formed during D1a, D1b and D2 show a transition from T =480–540 °C (during D1a) to T =570–660 °C (during D1b), corresponding to a slight pressure-increase from 0.75–0.95 GPa to 0.85–1.15 GPa. D2 greenschist retrogression corresponds to a pressure and temperature decrease ( T <400–550 °C and P <0.3–0.4 GPa). This P–T– deformation–time path is inferred to be the result of uplift from a depth of c. 35 km, after Palaeozoic subduction and continental collision; it is consistent with models postulated for other metamorphic units of the Variscan Belt in Europe. This is the first documented example in the Southern Alps of temperature-prograde metamorphism before Palaeozoic collision. 相似文献
19.
K. MIYAZAKI I. ZULKARNAIN J. SOPAHELUWAKAN & K. WAKITA 《Journal of Metamorphic Geology》1996,14(5):549-563
High-pressure metamorphic rocks exposed in the Bantimala area, c . 40 km north-east of Ujung Pandang, were formed as a Cretaceous subduction complex with fault-bounded slices of melange, chert, basalt, turbidite, shallow-marine sedimentary rocks and ultrabasic rocks. Eclogites, garnet–glaucophane rocks and schists of the Bantimala complex have estimated peak temperatures of T =580–630 °C at 18 kbar and T =590–640 °C at 24 kbar, using the garnet–clinopyroxene geothermometer. The garnet–omphacite–phengite equilibrium is used to estimate pressures. The distribution coefficient K D1 =[( X pyr )3 ( X grs )6 /( X di )6 ]/[(Al/Mg)M2,wm (Al/Si)T2,wm ]3 among omphacite, garnet and phengite is a good index for metamorphic pressures. The K D1
20.
Well-preserved garnet growth zoning in granulite from the Dabie Mountains, central China 总被引：9，自引：1，他引：8
Ultra-high pressure eclogites and granulites both occur in the Dabie Mountains, central China. A garnet porphyroblast from felsic granulite in the Dabie Mountains has been analysed for compositional zoning by electron microprobe. Two segments of the porphyroblast have opposite compositional variations. Segment I (from centre outward 9 mm to analytical point 18) has decreasing XSps and increasing XPyr , while Segment II (from analytical point 18, 1 mm outward to the rim) has increasing XSps and XAlm and decreasing XPyr and XGrs . The compositional zoning in segment I is considered as growth zoning and that in Segment II as diffusive retrograde zoning. Garnet growth zoning records a P–T path prior to the peak granulite metamorphism. The minimum P – T conditions are estimated to be 1.35 GPa and 850 °C for peak metamorphism, based on the highest Mg/(Fe+Mg) composition in the garnet (analytical point 18) and matrix hypersthene, biotite and plagioclase. A symplectitic corona surrounds the porphyroblast and appears to have formed at 0.6 GPa and 700 °C. The well-preserved growth zoning in garnet suggests a short residence time for the granulite at peak metamorphism and thus rapid tectonic uplift history. The P–T path is consistent with that of ultra-high-pressure eclogite in the area. Tectonic movements during a collisional event could have brought both the granulite and the eclogite to their present positions. 相似文献