Aerosol optical depth at ALOMAR Observatory (Andøya, Norway) in summer 2002 and 2003     

CARLOS TOLEDANO  VICTORIA CACHORRO  ALBERTO BERJÓN  MAR SORRIBAS  RICARDO VERGAZ  ÁNGEL DE FRUTOS  MANUEL ANTÓN  MICHAEL GAUSA 《Tellus. Series B, Chemical and physical meteorology》2006,58(3):218-228

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Palaeoenvironmental significance of Late Permian palaeosols in the South‐Eastern Iberian Ranges,Spain     

RAÚL DE LA HORRA  Ma ISABEL BENITO  JOSE LÓPEZ‐GÓMEZ  ALFREDO ARCHE  JOSÉ F. BARRENECHEA  JAVIER LUQUE 《Sedimentology》2008,55(6):1849-1873

The Late Permian (Wuchiapingian) Alcotas Formation in the SE Iberian Ranges consists of one red alluvial succession where abundant soil profiles developed. Detailed petrographical and sedimentological studies in seven sections of the Alcotas Formation allow six different types of palaeosols, with distinctive characteristics and different palaeogeographical distribution, to be distinguished throughout the South‐eastern Iberian Basin. These characteristics are, in turn, related to topographic, climatic and tectonic controls. The vertical distribution of the palaeosols is used to differentiate the formation in three parts from bottom to top showing both drastic and gradual vertical upwards palaeoenvironmental changes in the sections. Reconstruction of palaeoenvironmental conditions based on palaeosols provides evidence for understanding the events that occurred during the Late Permian, some few millions of years before the well‐known Permian‐Triassic global crisis.  相似文献   

THE CHEMISTRY OF SUBMARINE CEMENT FORMATION AT DOHAT HUSSAIN IN THE PERSIAN GULF     

K. DE  GROOT 《Sedimentology》1969,12(1-2):63-68

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The Physico-Chemical Properties of a Subducted Slab from Garnet Zonation Patterns (Sesia Zone, Western Alps)   总被引：3，自引：0，他引：3  

KONRAD-SCHMOLKE  MATTHIAS; BABIST  JOCHEN; HANDY  MARK R.; O'BRIEN  PATRICK J. 《Journal of Petrology》2006,47(11):2123-2148

Garnets in continentally derived high-pressure (HP) rocks ofthe Sesia Zone (Western Alps) exhibit three different chemicalzonation patterns, depending on sample locality. Comparisonof observed garnet zonation patterns with thermodynamicallymodelled patterns shows that the different patterns are causedby differences in the water content of the subducted protolithsduring prograde metamorphism. Zonation patterns of garnets inwater-saturated host rocks show typical prograde chemical zonationswith steadily increasing pyrope content and increasing XMg,together with bell-shaped spessartine patterns. In contrast,garnets in water-undersaturated rocks have more complex zonationpatterns with a characteristic decrease in pyrope and XMg betweencore and inner rim. In some cases, garnets show an abrupt compositionalchange in core-to-rim profiles, possibly due to water-undersaturationprior to HP metamorphism. Garnets from both water-saturatedand water-undersaturated rocks show signs of intervening growthinterruptions and core resorption. This growth interruptionresults from bulk-rock depletion caused by fractional garnetcrystallization. The water content during burial influences significantly thephysical properties of the subducted rocks. Due to enhancedgarnet crystallization, water-undersaturated rocks, i.e. thoselacking a free fluid phase, become denser than their water-saturatedequivalents, facilitating the subduction of continental material.Although water-bearing phases such as phengite and epidote arestable up to eclogite-facies conditions in these rocks, dehydrationreactions during subduction are lacking in water-undersaturatedrocks up to the transition to the eclogite facies, due to thethermodynamic stability of such hydrous phases at high P–Tconditions. Our calculations show that garnet zonation patternsstrongly depend on the mineral parageneses stable during garnetgrowth and that certain co-genetic mineral assemblages causedistinct garnet zonation patterns. This observation enablesinterpretation of complex garnet growth zonation patterns interms of garnet-forming reactions and water content during HPmetamorphism, as well determination of detailed P–T paths. KEY WORDS: dehydration; high-pressure metamorphism; Sesia Zone; subduction; thermodynamic modelling  相似文献   

中朝地台东北缘地区的地震层析成像   总被引：24，自引：5，他引：24       下载免费PDF全文

卢造勋  蒋秀琴  潘科  白云  姜德录  肖立萍  刘建华  刘福田  陈辉  何建坤 《地球物理学报》2002,45(3):338-351

根据中朝地台东北缘地区 (东经 1 1 7°0 0′— 1 2 6°0 0′ ,北纬 36°0 0′— 44°0 0′) 1 980— 1 997年的 380 0 0余条P波走时数据 ,利用正交投影法重建了该区地壳和上地幔的三维速度结构 .通过分析及同人工地震测深剖面的详细对比 ,证明了成像结果的可靠性 .结果表明 :中朝地台东北缘地区地壳上地幔介质存在显著的横向不均匀性 ,直至 1 2 0km深度处依然明显 ;地壳上部的速度图像清楚地反映了不同岩石单元的分布与该区不同性质的基岩分布基本吻合 ;从上、中地壳的速度图像中发现了研究区存在海城、朝阳、义县、丹东南、唐山等几个低速异常区(即速度逆反层区 ) ,其中海城、唐山、朝阳等地区的壳内低速层已由深地震测深资料所证实 ;研究区陆地发生的几次强震均发生于壳内低速层上方的高速脆性介质内 ,而渤海发生的强震 ,此现象不明显 ,但都发生于横向介质速度显著突变的位置 ;在地壳不同深度上发现了普兰店至山海关横跨渤海的北西向低速异常带 ;地震层析二维速度图像与深地震测深资料的对比表明 ,研究区利用地震层析成像技术 ,在一定条件下可以获得与人工地震测深相似的效果  相似文献   

A ternary solid solution model for omphacite and its application to geothermobarometry of eclogites from the Middle Adula nappe (Central Alps, Switzerland)   总被引：7，自引：0，他引：7  

C. MEYRE  C. DE CAPITANI  & J. H. PARTZSCH 《Journal of Metamorphic Geology》1997,15(6):687-700

A ternary solid solution model for omphacite with the end-members jadeite (NaAlSi₂O₆), diopside (CaMgSi₂O₆) and hedenbergite (CaFeSi₂O₆) was derived from experimental data from the literature. The subregular solution model, fitted by linear programming, is best suited to omphacites with very little aegirine component in common eclogites. Applying this solution model to the calculation of equilibrium phase diagrams of eclogites from the Adula nappe (Central Alps, Switzerland) results in large stability fields for common eclogite assemblages (garnet+omphacite+quartz+H₂O±kyanite). Within this field the compositions of garnet and omphacite show very little variation. A precise determination of the peak-pressure and temperature is not possible. The occurrence of amphibole, overgrowing the peak-pressure assemblage in fresh eclogite, suggests retrograde re-equilibration, still under eclogite facies conditions. The computation of isopleths for garnet and pyroxene end-members allows the estimation of the pressure and temperature conditions of this re-equilibration event (19–21  kbar, c .  700 °C).  相似文献   

Flow dynamics and geomorphology of a trough blowout   总被引：6，自引：0，他引：6  

PATRICK A. HESP  ROBERT HYDE† 《Sedimentology》1996,43(3):505-525

The dynamics and geomorphological development of a trough blowout located at Fiona Beach in the Myall Lakes National Park in NSW, Australia, are examined. Wind speeds, velocities and flow structure were measured utilizing an array of miniature Rimco cup anemometers, Gill bivane and UVW instruments, and wind vanes. Flow measurements indicate that when the wind approaches the trough blowout parallel to the throat orientation, jets occur both in the deflation basin and along the erosional walls, relative flow deceleration and expansion occurs up the depositional lobe, jets are formed over the depositional lobe crest accompanied by downwind flow separation on the leeward side of the lobe, and flow separation and the formation of corkscrew vortices occur over the crests of the erosional walls. Maximum erosion and transport occurs up the deflation basin and onto the depositional lobe. Trough blowout morphologies are explained as a function of these flow patterns. When the wind approaches the blowout obliquely, the flow is steered considerably within the blowout, and the degree and complexity of topographic steering is dependent on the blowout topography. The flow is usually extremely turbulent and large corkscrew vortices are common. The local topography of a blowout can be very important in determining overall sand transport and blowout evolutionary conditions and paths. Estimates of potential sand transport within the blowout may be up to two orders of magnitude lower than actual rates if remotely sensed wind data are used.  相似文献   

A shift towards wetter and windier conditions in southern Sweden around the prominent solar minimum 2750 cal a BP          下载免费PDF全文

ANETTE MELLSTRÖM  NATHALIE VAN DER PUTTEN  RAIMUND MUSCHELER  RIXT DE JONG  SVANTE BJÖRCK 《第四纪科学杂志》2015,30(3):235-244

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Potential seasonal calibration for palaeoenvironmental reconstruction using skeletal microstructures and strontium measurements from the cold‐water coral Lophelia pertusa          下载免费PDF全文

VINCENT MOUCHI  QUENTIN G. CROWLEY  ANDREW L. JACKSON  FRANK MCDERMOTT  XAVIER MONTEYS  MARC DE RAFÉLIS  JOSÉ LUIS RUEDA  FRANCK LARTAUD 《第四纪科学杂志》2014,29(8):803-814

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A Middle Palaeolithic site in the southern North Sea: investigating the archaeology and palaeogeography of Area 240          下载免费PDF全文

L. TIZZARD  A. R. BICKET  J. BENJAMIN  D. DE LOECKER 《第四纪科学杂志》2014,29(7):698-710

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