Timing of Proterozoic magmatism in the Sunsas belt,Bolivian Precambrian Shield,SW Amazonian Craton     

Ingrid M.Nedel  Reinhardt A.Fuck  Amarildo S.Ruiz  Gerardo R.Matos-Salinas  Alanielson da C.D.Ferreira 《地学前缘(英文版)》2021,12(6):277-293

We present new U-Pb zircon and monazite ages from the Sunsas belt granitic magmatism in Bolivia,SW Amazonian Craton.The geochronological results revealed four major magmatic events recorded along the Sunsas belt domains.The older igneous event formed a granitic basement coeval to the Rio Apa Terrane(1.95-1.85 Ga)in the southern domain.The second magmatic episode is represented by 1.68 Ga granites associated to the Paraguá Terrane(1.69-1.66 Ga)in the northern domain.The 1.37-1.34 Ga granites related to San Ignacio orogeny represent the third and more pervasive magmatic event,recorded throughout the Sunsas belt.Moreover,magmatic ages of～1.42 Ga revealed that the granitogenesis asso-ciated to the Santa Helena orogeny also affected the Sunsas belt,indicating that it was not restricted to the Jauru Terrane.Lastly,the 1.10-1.04 Ga youngest magmatism was developed during the Sunsas oro-geny and represents the final magmatic evolution related to Rodinia assembly.Likewise,the 1.95-1.85 and 1.68 Ga inherited zircon cores obtained in the～1.3 Ga and 1.0 Ga granite samples suggest strong par-tial melting of the Paleoproterozoic sources.The 1079±14 Ma and 1018±6 Ma monazite crystallization ages can be correlated to the collisional tectono-thermal event of the Sunsas orogeny,associated to reac-tions of medium-to high-grade metamorphism.Thus,the Sunsas belt was built by heterogeneous 1.95-1.85 Ga and 1.68 Ga crustal fragments that were reworked at 1.37-1.34 Ga and 1.10-1.04 Ga related to orogenic collages.Furthermore,the 1.01 Ga monazite age suggests that granites previously dated by zir-con can bear evidence of a younger thermal history.Therefore,the geochronological evolution of the Sunsas belt may have been more complex than previously thought.  相似文献   

Age of the Pomeranian ice‐marginal position in northeastern Germany determined by Optically Stimulated Luminescence (OSL) dating of glaciofluvial sediments     

CHRISTOPHER LÜTHGENS  MARGOT BÖSE  FRANK PREUSSER 《Boreas: An International Journal of Quaternary Research》2011,40(4):598-615

Lüthgens, C., Böse, M. & Preusser, F. 2011: Age of the Pomeranian ice‐marginal position in northeastern Germany determined by Optically Stimulated Luminescence (OSL) dating of glaciofluvial sediments. Boreas, 10.1111/j.1502‐3885.2011.00211.x. ISSN 0300‐9843 The Pomeranian ice margin is one of the most prominent ice‐marginal features of the Weichselian glaciation in northern Europe. Previous results of surface‐exposure dating (SED) of this ice margin disagree with established chronologies and ice retreat patterns, i.e. are much younger than previously expected. We crosscheck the age of the Pomeranian ice‐marginal position in northeastern Germany using single‐grain quartz Optically Stimulated Luminescence (OSL) dating of glaciofluvial sediments. OSL dating indicates an active ice margin between 20.1±1.6 ka and 19.4±2.4 ka forming outwash plains attributed to the Pomeranian ice‐marginal position. On the basis of these results, we suggest a critical reassessment of previous SED data available for the Pomeranian ice‐marginal position within their respective regional geomorphological contexts. From a process‐based point of view, SED ages derived from glacigenic boulders document the stabilization of the landscape after melting of dead ice and landscape transformation under periglacial conditions rather than the presence of an ice margin. SED indicates a first phase of boulder stabilization at around 16.4±0.7 ka, followed by landscape stabilization within the area attributed to the recessional Gerswalder subphase around 15.2±0.5 ka. A final phase of accumulation of glaciolacustrine and glaciofluvial sediments at around 14.7±1.0 ka documents the melting of buried dead ice at that time.  相似文献   

Eemian and Early Weichselian environments in southern Sweden: a multi‐proxy study of till‐covered organic deposits from the Småland peneplain     

GEOFFREY LEMDAHL  ANNA BROSTRÖM  LARS HEDENÄS  KRISTINA ARVIDSSON  SOFIA HOLMGREN  MARIE‐JOSÉ GAILLARD  PER MÖLLER 《第四纪科学杂志》2013,28(7):705-719

  相似文献   

Interpolation de variables régionales et cartographie automatique: modèle triangulaire hydrologique (MTH) / Interpolation of regional variables and automatic drawing of isoplets     

HIZIR ÖNSOY  C. BOCQUILLON 《水文科学杂志》2013,58(3):297-306

Abstract

The degree of relationship between hydrological variables being independent of time series properties is especially related to the distance between gauging stations of these variables. The linear character of these variables without extreme deviation in time makes possible the use of a new method of interpolation. Following is an explanation of a method which generalizes methods of linear interpolation of two points. Computing the variable values at each point, automatic drawing of isoplets and the water height in a basin can be easily computed by this method.  相似文献   

Spillway design floods in Sweden: I. New guidelines     

STEN BERGSTRÖM  JOAKIM HARLIN  GÖRAN LINDSTRÖM 《水文科学杂志》2013,58(5):505-519

Abstract

The new Swedish guidelines for the estimation of design floods for dams and spillways are presented, with emphasis on high-hazard dams. The method is based on a set of regional design precipitation sequences, rescaled for basin area, season and elevation above sea level, and a full hydrological model. A reservoir operation strategy is also a fundamental component of the guidelines. The most critical combination of flood generating factors is searched by systematically inserting the design precipitation sequence into a ten year climatological record, where the initial snowpack has been replaced by a statistical 30-year snowpack. The new guidelines are applicable to single reservoir systems as well as more complex hydroelectric schemes, and cover snowmelt floods, rain floods and combinations of the two. In order to study the probabilities of the computed floods and to avoid regional inconsistencies, extensive comparisons with observed floods and frequency analyses have been carried out.  相似文献   

The Congo Basin forests in a changing climate: Policy discourses on adaptation and mitigation (REDD+)     

Olufunso A. Somorin  H. Carolyn Peach Brown  Ingrid J. Visseren-Hamakers  Denis J. Sonwa  Bas Arts  Johnson Nkem 《Global Environmental Change》2012,22(1):288-298

This paper discusses the discourses on climate change adaptation and mitigation that are currently at the forefront in the Congo Basin. On mitigation, the forests have enormous opportunities to contribute to the reducing emissions from deforestation and forest degradation (REDD+) mechanism. But the forest itself and its multiple dependent societies and sectors need to adapt to potential climate risks. Hence, actors are debating the design of climate change policy in the forest sector. Theoretically, we combine the agency-focus of frame analysis and discourse theory to analyze how different agents hold frames on climate change adaptation and mitigation policies in the region. This paper draws upon interviews with 103 different actors from government, international organizations, non-governmental organizations, research institutions and private sector in three countries: Cameroon, Central African Republic (CAR) and Democratic Republic of Congo (DRC). Three discourses were found on policy response to climate change in the forest sector: mitigation policy only, separated policy on adaptation and mitigation, and an integrated policy on adaptation and mitigation. The various frames articulated around each discourse by the coalitions include elements of: costs and benefits, scale of operation, effectiveness, financial resources and implementation mechanisms. Overall, the mitigation discourse, through its mix of actors, resources and interests seems to be stronger than the adaptation discourse. The paper finally outlines a number of implications of the discourses for policy design.  相似文献   

Kohala revisited     

Albrecht W. Hofmann  Mark D. Feigenson  Ingrid Raczek 《Contributions to Mineralogy and Petrology》1987,95(1):114-122

We present new isotopic data for Sr and Nd in basalts and alkalic volcanics from Kohala volcano, Hawaii, which had previously been described by Feigenson et al. (1983). These data complement our own isotopic data presented in that paper and those given in the companion paper by Lanphere and Frey (1986). We show that in spite of appearances to the contrary, there is no significant analytical bias in our previously published analyses. Accidental sampling bias and one erroneous value prevented us from recognizing the isotopic heterogeneity in our previously published data. The new data both confirm the Sr-isotopic distinction between Pololu and Hawi volcanics discovered by Lanphere and Frey and narrow the gap between them significantly. The two data sets agree for the Hawi samples, but the mean ⁸⁷Sr/⁸⁶Sr=0.703651±13 for our Pololu basalts is significantly lower than the mean ⁸⁷Sr/⁸⁶Sr= 0.703748±18 found by Lanphere and Frey. The Ndisotopic ratios are also heterogeneous, but they overlap for the two formations. We agree with the assessment of Lanphere and Frey that some of our samples originally classified as belonging to the Hawi Formation are actually derived from the uppermost Pololu Formation, but with some stratigraphic ambiguities remaining.We believe that our previous results of inverse modelling are valid for the tholeiitic and moderately alkalic Pololu Formation despite the isotopic heterogeneity because this heterogeneity does not correlate with the trace element chemistry of the Pololu samples.The severe depletion of Sc, which correlates with decreasing CaO/Al₂O₃ ratios and increasing Yb concentrations, confirms the importance of clinopyroxene fractionation in the evolved lavas of the Hawi Formation. In addition, apatite precipitation did fractionate the P/Ce ratios in the more evolved Hawi lavas, but its effect on the REE abundances is still uncertain and may not be significant.The MgO — P₂O₅ plot of Lanphere and Frey does not provide compelling evidence against a simple genetic relationship between Pololu and Hawi lavas. The internal consistency of the (fractionation corrected) trace element ratios such as Ba/Ce indicates that Ba is depleted in both the Hawi and the Pololu sources and that these sources do have similar chemistry.Finally, we show that contrary to the conclusions of Lanphere and Frey the REE patterns of Kohala volcanics can be generated from sources with only slightly negatively sloping REE patterns without involvement of garnet, as was indicated by the formal inversion analysis. Models which include garnet yield more highly anomalous source abundance patterns and calculated bulk-source partition coefficients which are inconsistent with the presence of garnet. The persistence of residual garnet is also inconsistent with the absence of significant heavy-REE fractionation among the Pololu basalts.  相似文献   

Hydraulic properties of the crystalline basement   总被引：1，自引：1，他引：1  

Ingrid Stober  Kurt Bucher 《Hydrogeology Journal》2007,15(2):213-224

Hydraulic tests in boreholes, up to 4.5 km deep, drilled into continental crystalline basement revealed hydraulic conductivity (K) values that range over nine log-units from 10⁻¹³−10⁻⁴ m s⁻¹. However, K values for fractured basement to about 1 km depth are typically restricted to the range from 10⁻⁸ to 10⁻⁶ m s⁻¹. New data from an extended injection test at the KTB research site (part of the Continental Deep Drilling Program in Germany) at 4 km depth provide K=5 10⁻⁸ m s⁻¹. The summarized K-data show a very strong dependence on lithology and on the local deformation history of a particular area. In highly fractured regions, granite tends to be more pervious than gneiss. The fracture porosity is generally saturated with Na–Cl or Ca–Na–Cl type waters with salinities ranging from <1 to >100 g L⁻¹. The basement permeability is well within the conditions for advective fluid and heat transport. Consequently, fluid pressure is hydrostatic and a Darcy flow mechanism is possible to a great depth. Topography-related hydraulic gradients in moderately conductive basement may result in characteristic advective flow rates of up to 100 L a⁻¹ m⁻² and lead to significant advective heat and solute transfer in the upper brittle crust. An erratum to this article can be found at  相似文献   

Petroleum inclusions in sedimentary basins: systematics, analytical methods and applications   总被引：21，自引：0，他引：21  

Ingrid Anne Munz   《Lithos》2001,55(1-4):195-212

Fluid dynamics in sedimentary basins is of tremendous interest, both from a scientific and an economic point of view. Integration between fluid inclusion and present-day fluid data provides the time aspect necessary for reconstruction of fluid flow paths, and can be used for mapping fluid dynamics both on a regional basin scale or on the more local scale of petroleum reservoirs. This paper presents a review of analytical and modelling methods for petroleum in fluid inclusions. Essentially, four types of data for petroleum inclusions can be established through analysis and modelling: (1) textures (which give indirect information of the time aspect), (2) fluid composition, (3) fluid properties and (4) pressure–temperature of trapping. During the last decade, development of analytical methods for determination of inclusion fluid compositions has taken place. Traditional correlation studies for characterisation of maturity and source facies may now therefore include fluid inclusion data. The development has also been directed towards an improved understanding of the physical properties of petroleum inclusions. Although these methods are in their early stages concerning precision and accuracy, data necessary for fluid flow modelling, such as fluid densities, viscosities, pressure and temperature, can be estimated.  相似文献   

Computation of 5-day temperature normals in western Europe and the Mediterranean area     

Kurt Bender  Ulrich Chorus  Raymond Nybro  Robert Sanderson  Ingrid Weiss 《Pure and Applied Geophysics》1957,38(1):265-285

Summary UsingCraddock's method of representing the annual temperature variation by a two-term harmonic form fitted to monthly means, the harmonic coefficients of 63 stations in western Europe and around the Mediterranean Sea, as well as the 5-day normals for 24 Mediterranean stations, were computed and tabulated. In addition, some of the harmonic coefficients were charted and isoplethed, showing very distinctly the influence of continentality and topography. These charts, together withCraddock's charts for northern and northwestern Europe, provide fairly complete coverage of Europe and the Mediterranean area.This paper was prepared in the offices of the Technical Support Division of the 2d Weather Wing, United States Air Force, as a matter of routine business. The information contained herein was presented at the 5th Meeting of the Italian Society of Geophysics and Meteorology by Dr.Ingrid Weiss (Genoa: 23–25 April 1957). Since the paper is of general interest to all meteorologists of the Mediterranean area, it is published here with the permission of the originating agency as «Mémoire No. 3 du Centre International de Recherches sur la Météorologie de la Méditerranée (CIRMM)».  相似文献