PREFACE: THE MOUNTAIN CRYOSPHERE – A HOLISTIC VIEW ON PROCESSES AND THEIR INTERACTIONS     

STEPHAN GRUBER  MARKUS EGLI  ISABELLE GÄRTNER‐ROER  MARTIN HOELZLE 《Geografiska Annaler: Series A, Physical Geography》2012,94(2):177-182

Gruber, S., Egli, M., Gärtner‐Roer, I. and Hoelzle, M., 2012. Preface: The mountain cryosphere – a holistic view on processes and their interactions. Geografiska Annaler: Series A, Physical Geography, ??, ??–??. doi :10.1111/j.1468‐0459.2012.00468.x  相似文献   

Architecture of vertically stacked fluvial deposits,Atane Formation,Cretaceous, Nuussuaq,central West Greenland     

MARIA A. JENSEN  GUNVER KRARUP PEDERSEN 《Sedimentology》2010,57(5):1280-1314

Excellent exposures of thick, multistorey, fluvial deposits from the deltaic Atane Formation on south‐east Nuussuaq, central West Greenland, show the architecture of up to 100 m thick continuously aggrading fluvial depositional complexes. The succession comprises vertically stacked channel belt sandstones separated by thin floodplain deposits, with little to no incision between storeys. Architectural elements and palaeocurrent patterns of channel deposits indicate deposition in large, relatively stable, low‐sinuosity rivers, probably located within an incised valley. Gradual transitions from channel to floodplain deposits accompanied by a gradual change from floodplain to spillover sand suggest avulsion on the floodplain as a possible mechanism for the vertically alternating channel and floodplain deposits. Despite its relative proximity to contemporaneous sea‐level (ca 35 km upstream from the palaeo‐shoreline) the depositional complex is entirely non‐marine. The aggrading nature of the deposits suggests a continuously rising base level coupled with a high and steady sediment supply. Vertical alternations between floodplain and channel deposits may be forced by subtle interruptions in this balance or autocyclic mechanisms on the floodplain. This study provides an example of aggrading lowstand/non‐marine transgressive systems tract deposits.  相似文献   

The subglacial record of northern Hudson Bay: insights into the Hudson Strait Ice Stream catchment     

MARTIN ROSS  PATRICK LAJEUNESSE  KEVIN G. A. KOSAR 《Boreas: An International Journal of Quaternary Research》2011,40(1):73-91

Ross, M., Lajeunesse, P. & Kosar, K. G. A. 2010: The subglacial record of northern Hudson Bay: insights into the Hudson Strait Ice Stream catchment. Boreas, 10.1111/j.1502‐3885.2010.00176.x. ISSN 0300‐9483. In this paper, we present new insights into the glacial dynamics and potential configuration of the Hudson Strait Ice Stream catchment in the northern Hudson Bay–western Hudson Strait region. Our reconstruction is based on new field observations and till compositional data from Southampton Island, remote sensing imagery and multibeam bathymetric data from the Hudson Bay sea floor, as well as on a re‐examination of previously published data from this vast region. Our findings suggest that, during the late Quaternary, the HSIS catchment consisted of a number of ice‐stream tributaries feeding a curvilinear trunk that potentially extended into western Hudson Bay. In contrast to previous interpretations, the occurrence of fluted bedrock hills, over‐deepened basins, Dubawnt erratics and carbonaceous till on the islands at the head of Hudson Strait is taken to imply that cold‐based conditions did not prevail on these islands. The upland area of Southampton Island and the surrounding channels played an important role in controlling the location of the main tributaries, with the higher central terrain forming a large inter‐ice‐stream zone lacking carbonate detritus. Coats Island contains abundant evidence of vigorous ice flow, such as mega‐scale glacial lineations (MSGLs). MSGLs also occur on the sea floor southwest of Coats Island but the sea‐floor imprint is highly discontinuous. Observations on the western Hudson Bay mainland show evidence of southeastward fast ice flow that is spatially consistent with the Dubawnt dispersal train. Despite the geomorphological discontinuities, this may indicate that the HSIS onset zone extended far inside the Laurentide Ice Sheet and across contrasting geological domains.  相似文献   

Re‐evaluation of the Last Glacial Maximum typesite at Dimlington,UK     

MARK D. BATEMAN  PAUL C. BUCKLAND  MARTIN A. WHYTE  ROBERT A. ASHURST  CLAIRE BOULTER  EVA PANAGIOTAKOPULU 《Boreas: An International Journal of Quaternary Research》2011,40(4):573-584

Bateman, M. D., Buckland, P. C., Whyte, M. A., Ashurst, R. A., Boulter, C. & Panagiotakopulu, E. 2011: Re‐evaluation of the Last Glacial Maximum typesite at Dimlington, UK. Boreas, 10.1111/j.1502‐3885.2011.00204.x. ISSN 0300‐9483. Recent erosion has allowed re‐examination of the stratigraphy and sampling for both optically stimulated luminescence dating and palaeoecological analysis of the key sections in the Last Glacial Maximum deposits at Dimlington in East Yorkshire, England. Both stratigraphy and fossil insect evidence support a subaerial origin for laminated and cross‐bedded sediments between two diamictons previously interpreted as synchronous. The fossil biota indicates conditions similar to those of a pond on sandur in the high Arctic, with little or no vegetation cover. The existence of distinct oscillations of the ice front is indicated. The first, within the period 21.7–16.2 ka, appears coincident with climate warming, as deduced from Greenland ice‐core evidence, and is interpreted as an ice stream associated with changing flow patterns within the British–Irish Ice Sheet (BIIS). The second, dating between 16.2 and 15.5 ka, appears to coincide with a climatic cooling, although current models show that the BIIS had by this period already retreated back to ice centres. This new evidence supports the view that the eastern sector of the BIIS did not reach its maximal extent synchronously with other parts of the BIIS.  相似文献   

The Turiy Massif, Kola Peninsula, Russia: Isotopic and Geochemical Evidence for Multi-source Evolution   总被引：6，自引：1，他引：6  

DUNWORTH  ELIZABETH ANN; BELL  KEITH 《Journal of Petrology》2001,42(2):377-405

The Turiy Massif, lying within the Kandalaksha Graben, and onthe southern coast of the Kola Peninsula, contains carbonatites,phoscorites, melilitolites, ijolites and pyroxenites withinone central and four surrounding satellite complexes. Sr–Ndisotopic data from the central complex phoscorites and carbonatites,and the nearby Terskii Coast kimberlites, combined with otherrecently published data on the Devonian Kola Alkaline Province,allow us to redefine the position of the Kola Carbonatite Line(KCL) of Kramm (European Journal of Mineralogy 5, 985–989,1993). We propose that the revised-KCL mantle sources includea lower-mantle plume, and a second enriched source, which alsocontributed to the Terskii Coast and Archangelsk kimberlites.The Turiy Massif silicate rocks and northern complex carbonatiteshave more enriched isotopic signatures than the distinct, anddepleted signatures of the central complex phoscorites and carbonatites,particularly with respect to  相似文献   

Progressive Low-Grade Metamorphism of a Black Shale Formation, Central Swiss Alps, with Special Reference to Pyrophyllite and Margarite Bearing Assemblages   总被引：1，自引：0，他引：1  

FREY  MARTIN 《Journal of Petrology》1978,19(1):95-135

The unmetamorphosed equivalents of the regionally metamorphosedclays and marls that make up the Alpine Liassic black shaleformation consist of illite, irregular mixed-layer illite/montmorillonite,chlorite, kaolinite, quartz, calcite, and dolomite, with accessoryfeldspars and organic material. At higher grade, in the anchizonalslates, pyrophyllite is present and is thought to have formedat the expense of kaolinite; paragonite and a mixed-layer paragonite/muscovitepresumably formed from the mixed-layer illite/montmorillonite.Anchimetamorphic illite is poorer in Fe and Mg than at the diageneticstage, having lost these elements during the formation of chlorite.Detrital feldspar has disappeared. In epimetamorphic phyllites, chloritoid and margarite appearby the reactions pyrophyllite + chlorite = chloritoid + quartz+ H₂O and pyrophyllite + calcite ± paragonite = margarite+ quartz + H₂O + CO₂, respectively. At the epi-mesozone transition,paragonite and chloritoid seem to become incompatible in thepresence of carbonates and yield the following breakdown products:plagioclase, margarite, clinozoisite (and minor zoisite), andbiotite. The maximum distribution of margarite is at the epizone-mesozoneboundary; at higher metamorphic grade margarite is consumedby a continuous reaction producing plagioclase. Most of the observed assemblages in the anchi-and epizone canbe treated in the two subsystems MgO (or FeO)-Na₂O–CaO–Al₂O₃–(KAl₃O₅–SiO₂–H₂O–CO₂).Chemographic analyses show that the variance of assemblagesdecreases with increasing metamorphic grade. Physical conditions are estimated from calibrated mineral reactionsand other petrographic data. The composition of the fluid phasewas low in X_CO2 throughout the metamorphic profile, whereasX_CH4 was very high, particularly in the anchizone where a_H2Owas probably as low as 0.2. P-T conditions along the metamorphicprofile are 1–2 kb/200–300 °C in the anchizone(Glarus Alps), and 5 kb/500–550 °C at the epi-mesozonetransition (Lukmanier area). Calculated geothermal gradientsdecrease from 50 °C/km in the anchimetamorphic Glarus Alpsto 30 °C/km at the epi-mesozone transition of the Lukmanierarea.  相似文献   

Analyse de 47 Echantillons Géochimiques de Référence par Fluorescence-X (Cu, Ga, Ni, Zn) Et par Absorption Atomique (Cu, Ni, Zn)     

M. QUINTIN  A. MARTIN  A. M. de  KERSABIEC 《Geostandards and Geoanalytical Research》1978,2(2):199-209

47 étalons géochimiques internationaux dont les huit nouveaux étalons de l'USGS ont été analysés par fluorescence-X et absorption atomique pour Ni, Cu, Zn et par fluorescence-X pour Ga.
Les auteurs développment ici pour la fluores-cence-X les problèmes concernant le choix des fonds, le calcul du fond véritable sous-jacent au pic mesuré, les impuretés des tubes et de l'appareillage. Une méthode directe sur échantillon pulvérulent, non destructive, sans aucune préparation est utilisée.
Trois systèmes de fluorescence-X utilisant deux appareillages (Philips PW 1540 et Siemens SSRS 1) et deux tubes molybdène et or sont confrontés et les moyennes comparée à celles d'une méthode d'absorption atomique par mise en solution de l'échantillon (IL 353).
Les résultats obtenus sont comparés soit aux valeurs recommandées, soit aux moyennes calculées à partir de la littérature. On discute tant les accords que les divergences.  相似文献   

THE CULTURAL GEOGRAPHY OF GARDENS*     

MARIA ELISA CHRISTIE 《Geographical review》2004,94(3):iii-iv

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KITCHENSPACE,FIESTAS, AND CULTURAL REPRODUCTION IN MEXICAN HOUSE‐LOT GARDENS*     

MARIA ELISA CHRISTIE 《Geographical review》2004,94(3):368-390

ABSTRACT. The house‐lot garden in central Mexico is gendered space where changing cultural identities are negotiated, re‐created, and celebrated as “tradition” is continually redefined. No clear boundary separates the kitchen from the house‐lot garden or the private space of the household from the semipublic space of the community. During collective food preparation for religious fiestas, gendered reciprocity networks strengthen community relations and foster alliances between traditional neighborhoods and between communities in the region. At the intersection of everyday life and fiestas, food‐preparation spaces, or kitchenspaces, in the house‐lot garden are fertile areas in which to explore the cultural reproduction of nature‐society relations. They are vital to understanding gender, place, and culture in this region and represent people's symbolic connection with the land in increasingly urban contexts. This article analyzes the sense of place that Mexican women derive from their house‐lot gardens.  相似文献   

A Fluid-Dynamical Study of Crystal Settling in Convecting Magmas   总被引：1，自引：3，他引：1  

MARTIN  DANIEL; NOKES  ROGER 《Journal of Petrology》1989,30(6):1471-1500

Thermal convection in magma chambers is believed to be almostalways highly time-dependent, or ‘turbulent’, andpredicted convective velocities are commonly orders of magnitudelarger than settling velocities for typical crystals calculatedfrom Stokes' Law. To understand crystal settling in magma chamberswe have therefore undertaken a theoretical and experimentalstudy of particle settling in a turbulently convecting fluid. The regime of interest is where the ratio, S, of the Stokes'Law settling velocity, v_s, to the root mean square verticalcomponent of convective velocity, W, at mid-depth in the fluidis less than unity. Although v_s < W, settling is still possiblebecause convective velocities are height-dependent and mustdecrease to zero at the boundaries of the fluid. Particles immediatelyadjacent to the bottom boundary settle out with their full Stokes'settling velocities. At the same time, convection is vigorousenough to ensure that the distribution of particles in the fluidis uniform. It follows that the number of particles in suspensiondecays with time according to an exponential law, and the decayconstant is simply the ratio of v_s to h, the depth of the fluid.Experiments confirm this relationship, at least for low particleconcentrations, provided S < 0.5 and there is no re-entrainmentof particles from the floor of the tank. We apply this relationship to crystals in magma chambers andso calculate residence times for typical crystals. We find thatfor basaltic magmas the predicted residence times are smallcompared with the many thousands of years that a chamber takesto solidify if cooling is dominated by conduction through thecountry rock. We therefore conclude that crystal settling maybe an efficient differentiation mechanism. Significant magmaticevolution may, however, take place on time-scales that are competitivewith these residence times. If the settling of crystals is the rate-limiting step duringthe crystallization of a magma chamber it is expected that asteady state will be achieved at which the rate of supply ofcrystals into the convecting magma by crystallization balancesthe rate at which crystals settle out. We show how this ideacan explain both the lack of hydraulic equivalence in cumulaterocks and the commonly observed discrepancy between the relativeproportions of phenocrysts of various phases in fractionatedbasaltic lavas and the calculated relative proportions of thesemineral phases in the fractionating assemblage. Finally, anattempt is made to calculate the steady-state crystal contentof convecting magma chambers. Comparison of the predicted crystalcontents with the observed phenocryst contents of typical basalticlavas suggests that magma chambers may often cool more rapidlythan would be expected for conduction through the country rockalone.  相似文献