North European last glacial–interglacial transition (LGIT; 15–9 ka) tephrochronology: extended limits and new events     

C. S. M. Turney  K. Van Den Burg  S. Wastegrd  S. M. Davies  N. J. Whitehouse  J. R. Pilcher  C. Callaghan 《第四纪科学杂志》2006,21(4):335-345

High‐precision correlation of palaeoclimatic and palaeoenvironmental records is crucial for testing hypotheses of synchronous change. Although radiocarbon is the traditional method for dating late Quaternary sedimentary sequences, particularly during the last glacial–interglacial transition (LGIT; 15–9 ka), there are inherent problems with the method, particularly during periods of climate change which are often accompanied by major perturbations in atmospheric radiocarbon content. An alternative method is the use of tephras that act as time‐parallel marker horizons. Within Europe, numerous volcanic centres are known to have erupted during the LGIT, providing considerable potential for high‐precision correlation independent of past radiocarbon fluctuations. Here we report the first identification of the Vedde Ash and Askja Tephra in Ireland, significantly extending the known provenance of these events. We have also identified two new horizons (the Roddans Port Tephras A and B) and tentatively recognise an additional horizon from Vallensgård Mose (Denmark) that provide crucial additional chronological control for the LGIT. Two phases of the Laacher See Tephra (LST) are reported, the lower Laacher See Tephra (LLST) and probably the C2 phase of the Middle Laacher See Tephra (MLST‐C2) indicating a more northeasterly distribution of this fan than reported previously. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

Growth of the Namche Barwa Syntaxis and associated evolution of the Tsangpo Gorge: Constraints from structural and thermochronological data   总被引：4，自引：0，他引：4  

Diane Seward  Jean-Pierre Burg 《Tectonophysics》2008,451(1-4):282-289

The eastern syntaxis of the Himalaya, Namche Barwa, is dominated by a north-plunging antiform which began to decompress/grow at approximately 4 Ma. New fission-track analyses on both apatite and zircon, combined with previous geochronological ages, indicate that the Namche Barwa Dome also extended laterally while growing vertically. Zircon fission-track ages range from 17.6 to 0.2 Ma and have a strong relationship to the main faults of the region, including the Tertiary Tsangpo Suture, with the younger ages inside the fault bounds towards the syntaxis core on the Indian Plate and the older ages away from the fault. Apatite ages reveal that the dome has grown laterally and now impinges over the older faulted margin onto the Asian Plate. The dome is traversed by the Tsangpo which has followed the trace of the Suture for over 1300 km from its source to the entrance of the dome near Dania. As the Tsangpo crosses the dome it departs from the Suture but rejoins it some 60 km northeastwards. We construe that the Suture has been displaced by the growing antiform and as a consequence, the antecedent river has been “dragged” in a left-lateral sense along the exhuming north-plunging dome. Restoring the Suture to its position prior to 4 Ma reveals a path of the Tsangpo eastwards across the present southwestern position of the Namche Barwa indentation. This geometric reconstrunction implies that the Tsangpo and the Brahmaputra were always one and the same river. In addition, the Tsangpo was tectonically forced into juxtaposition with a tributary of the Jiali-Parlung which it probably then captured. The capture was due to tectonic forcing, in the last 4 Ma, rather than headward retreat of the paleo-Brahmaputra as has been previously suggested.  相似文献   

Exhumation during crustal folding in the Namche-Barwa syntaxis   总被引：6，自引：0，他引：6  

Jean-Pierre Burg  Philippe Davy  Peter Nievergelt  Felix Oberli  Diane Seward  Zhizhong Diao  Martin Meier 《地学学报》1997,9(2):53-56

Geological observation in the eastern end of the Himalaya shows that the Asia/India Suture is folded. Metamorphic rocks derived from India occur structurally below the suture, in the core of a regional antiform. Isotopic and fission track dating establish cooling-exhumation of rocks from c.30 km depth within the last 4 Myr. We argue that exhumation is caused by ～ 10 mm yr^-1 erosion coeval with crustal scale folding.  相似文献   

Hydraulic roughness over simple subaqueous dunes   总被引：2，自引：1，他引：1  

Jesper Bartholdy  Burg W. Flemming  Verner B. Ernstsen  Christian Winter  Alex Bartholom ä 《Geo-Marine Letters》2010,30(1):63-76

Detailed studies of flow over subaqueous dunes in laboratory flumes were used to suggest a virtual near-bed layer of twice the dune height in which the mean velocity is accelerated towards the crest by contraction. The mean flow velocity in this layer above the crest, transformed into friction velocity by means of the surface skin roughness, is shown to give values consistent with measured values. The resulting dimensionless shear stress due to skin friction is depth-independent, in contrast to that derived by means of often cited traditional methods. As a result of the relationship between dune height and the thickness of the near-bed layer, an expression for the expansion loss behind dunes was formulated and used to relate form resistance directly to dune height.  相似文献   

Himalayan metamorphism and deformations in the North Himalayan Belt (southern Tibet,China)   总被引：3，自引：0，他引：3  

J.P. Burg  M. Guiraud  G.M. Chen  G.C. Li 《Earth and Planetary Science Letters》1984,69(2):391-400

The Kangmar Massif which has been attributed to the North Himalayan Belt of two-mica granites in southern Tibet (China) is shown to be an orthogneiss in the core of a dome which displays an intermediate high-pressure type metamorphism, Himalayan in age (40 to 20 Ma) and above the Main Central Sheet. This metamorphism took place during high shear strain deformation, and it is not recorded to the west where North Himalayan plutons have developed contact metamorphism.  相似文献   

Regional shear variation in relation to diapirism and folding     

Jean-Pierre Burg 《Journal of Structural Geology》1987,9(8)

Regional structural trends in the Lévézou area (southern Massif Central, France) delineate an antiformal structure. Deformed granitoids display changes along strike in S---C plane relationships, and therefore in sense of shear. These variations are interpreted to be strain accommodation features that developed during the diapiric emplacement and folding of the granitoid sheets, and so cannot be used as kinematic indicators on a regional scale.  相似文献   

地下水水源保护区范围计算的KLF法及其在徐州张集地区的应用          下载免费PDF全文

毛媛媛  王连生  方瑞 《水科学进展》2006,17(6):808-811

详细介绍了地下水水源保护区范围的计算方法:Krijgsman-Lobo-Ferreira(KLF)法,分别推导出了正水流梯度方向、负水流梯度方向和垂直于地下水流方向保护区范围的计算公式,并就方法的适用性及参数取值等问题进行了探讨.在徐州张集地区应用的结果表明,KLF法提供了一种计算地下水保护区范围的便捷、科学、有效的方法,计算结果对于确定地下水源保护区范围及有效保护地下水源具有实际意义.  相似文献   

A review of the assessments of the major fisheries resources in South Africa     

CL de Moor  SJ Johnston  A Brandão  RA Rademeyer  JP Glazer  LB Furman 《African Journal of Marine Science》2015,37(3):285-311

The waters off South Africa's coastline boast a rich mix of commercially fished species. Quantitative assessments of these marine resources have developed from simple methods first applied in the 1970s, to models that encompass a wide range of methodologies. The more valuable resources have undergone regular assessments in recent decades, with frequencies closely related to the management approach employed for each fishery. Many of these assessments form the operating models used to simulation-test candidate management procedures. This paper provides a comprehensive review of the assessments of 11 of the most important fisheries resources in South Africa. Some assessments use simple biomass dynamics models, whereas others are a hybrid of age- and length-based models, each designed to model the specific characteristics of the resource and fishery concerned. Many of the assessments have been disaggregated by species/stock and/or area as related multispecies/stock/ distribution hypotheses have arisen. This paper explores the similarities and differences in the data available and the methods applied. The review indicates that, whereas the status of three of these resources cannot be estimated reliably at present, the status of six resources is considered to be reasonable to good, whereas that of abalone Haliotis midae and West Coast rock lobster Jasus lalandii remains poor.  相似文献   

Multiple mantle sources during island arc magmatism: U–Pb and Hf isotopic evidence from the Kohistan arc complex, Pakistan     

Urs Schaltegger  Gerold Zeilinger  Martin Frank  Jean-Pierre Burg 《地学学报》2002,14(6):461-468

ABSTRACT This paper presents high-precision U–Pb ages and initial Hf isotopic compositions of zircon from mafic to felsic rocks of the Kohistan Arc Complex, Pakistan. Three magmatic pulses tapping geochemically different reservoirs are distinguished. Partial melting of mantle with MORB-type isotopic characteristics generated 99–92-Ma-old magmas. Plutonism around 85 Ma tapped a more fertile mantle source, most likely consisting of a >600-Ma-old metasomatically enriched mantle, or of mantle contaminated by an old sedimentary component; 82-Ma-old felsic peraluminous dykes have MORB-type isotopic compositions considered to be inherited from remelting earlier magmas in the deep base of the arc. The isotopic results demonstrate several and rather rapid changes in melt source region during arc development. They also show that there was subordinate continental influence and negligible importance of slab components for the Hf budget during the generation of the Kohistan Arc Complex.  相似文献   

Low-temperature constraints on the Cenozoic thermal evolution of the Southern Rhodope Core Complex (Northern Greece)     

Alexandre Kounov  Eliane Wüthrich  Diane Seward  Jean-Pierre Burg  Daniel Stockli 《International Journal of Earth Sciences》2015,104(5):1337-1352

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