Floodfan sedimentation and gravitational anomalies in the Salar de Punta Negra,Northern Chile     

Ronald A. van Overmeeren  Johan H. Staal 《International Journal of Earth Sciences》1976,65(1):195-211

The Upper Tertiary inter-andean tectonic trough of the Salar de Punta Negra is being filled mainly through sporadic flash-floods by denudation products from the East (Andes). Borehole records up to 430 m deep suggest depositional conditions similar to the actual ones.Block tectonic movements with N-S and NNE-SSW directions from Upper Tertiary through Pleistocene affected the normal morphology of the fans.Gravity survey has corfirmed a tectonic origin of the basin. East of the Salar, a buried graben with an alluvial fill of 550–750 m thickness was found, which may contain a groundwater reservoir.

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Zusammenfassung Der jungtertiäre intra-andine Graben des Salars Punta Negra wurde durch sporadische Flutfächer vorwiegend aus dem Osten (Hochkordillere) gefüllt. Bohrungen bis 430 m Tiefe zeigen ähnliche Fanglomerate, wie sie heute entstehen.Verwerfungen mit N-S- und NNE-SSW-Richtungen zwischen Jungtertiär und Pleistozän beeinflussen die Morphologie der Schuttfächer.Gravimetrische Messungen ergaben, daß die Depression tektonisch angelegt ist. Östlich des heutigen Salars liegt ein verschütteter Graben mit einer alluvialen Füllung von mindestens 550–750 m Dicke. Hier könnte ein Grundwasser-Reservoir liegen.

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Resumen El graben intra-andino del Salar de Punta Negra de edad Terciario Superior ha sido esporádicamente rellenado por conos aluviales. Estos vienen principalmente del este desde la Alta Cordillera. Perforaciones que han llegado hasta 430 m de profundidad muestran fanglomerados semejantes a los que se forman actualmente.Una tectónica de bloques de dirección N-S y NNE-SSW entre el Terciario Superior y el Pleistoceno afectan la morfología de los conos aluviales.Mediciones gravimétricas permiten concluir que la depresión tiene origen tectónico. Al oriente del Salar aparece un graben relleno de materiales aluviales con una potencia entre 550–750 m. Este graben puede contener acuíferos profundos de utilidad local.

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Résumé Le graben intra-andin Cénozoïque Supérieur du Salar de Punta Negra se comble par des courants torrentueux sporadiques de produits de dénudation venant surtout de l'Est (Haute Cordillère). Des forages atteignant 430 m de profondeur suggèrent des conditions de dépôt similaires aux actuelles.Des failles N-S et NNE-SSW actives depuis le Cénozoïque Supérieur jusqu'au Pléistocène ont affecté la morphologie des cônes de déjection.Les mesures gravimétriques confirment l'origine tectonique du bassin de Punta Negra. A l'Est du Salar est situé un graben totalement enfoui de dépôts alluviaux d'une puissance d'environ 550–750 m, où des nappes aquifères exploitables sont susceptibles d'exister à grande profondeur.

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- Salars Punta Negra , . 430 , . - -- — -- . , , . Salars , 550–750 . .

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Metasedimentary “graben” and associated structures in the lagoonal Almere Member (Groningen Formation,The Netherlands)     

A.J. van Loon  A.J. Wiggers 《Sedimentary Geology》1976,16(4):237-254

The lagoonal Almere Member (Holocene) has a high silt content over large areas, which favours the formation of numerous meta- and postsedimentary features. A graben-like structure is described for the first time and the name “gravifossum” is proposed. A similar structure has also been observed in comparable sediments in northern France.Processes, leading to meta- and postsedimentary structures, are supposed to have interacted.  相似文献   

Mid-tertiary igneous activity in east Greenland — The Kialineq complex     

P. E. Brown  O. van Breeman  R. H. Noble  R. M. Macintyre 《Contributions to Mineralogy and Petrology》1977,64(1):109-122

The igneous rocks of the Kialineq area on the East Greenland coast at 67 ° N comprise, gabbro, acid-basic breccia and net-vein complexes, syenite and granite and minor volcanics. Rb-Sr whole-rock and mineral isochrons for the epizonal syenites, granites and acid-basic complexes indicate a consanguineous mantle origin at 35±2 m.y. B.P. in agreement with the age obtained by K-Ar dating of biotites and hornblendes. This igneous activity may be associated with major reorganisation of plate geometry in the North Atlantic and Arctic oceans at this time.  相似文献   

Search for purines and pyrimidines in the Murchison meteorite     

W. van der Velden  Alan W. Schwartz 《Geochimica et cosmochimica acta》1977,41(7):961-968

A 1 g interior sample of the Murchison CII meteorite was examined for the presence of purines and pyrimidines by dual-column, ion-exclusion chromatography and ultraviolet spectroscopy. Xanthine, not previously reported in meteorites, was found to be the major purine liberated by extraction with formic acid, with a concentration corresponding to 2.3 μg/g of meteorite. Guanine (0.1 ppm) and hypoxanthine (0.04 ppm) were also tentatively identified. The presence of adenine could not be confirmed. No pyrimidines were detected at concentrations higher than the background level (0.01 ppm) in water, formic acid or strong acid extracts. Silylation of the water extract, however, resulted in the appearance of 4-hydroxypyrimidine, 4-hydroxy-2-methylpyrimidine and 4-hydroxy-6-methylpyrimidine. These compounds are-though to be formed during the silylation procedure from contaminants present in the reagent.  相似文献   

Comment on the paper “Systematic variation in chemistry and Nd-Sr isotopes across a Caledonian calc-alkaline volcanic arc: Implications for source materials”, by M.F. Thirlwall     

O. van Breemen  B.J. Bluck 《Earth and Planetary Science Letters》1983,65(1):206-207

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The Clogging of Shallow Discharge Wells in the Netherlands River Region   总被引：1，自引：0，他引：1  

C.G.E.M. van  Beek W. F. Kooper 《Ground water》1980,18(6):578-586

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Sulfate-Reducing Bacteria in Ground Water from Clogging and Nonclogging Shallow Wells in the Netherlands River Region     

C.G.E.M. van  Beek D. van der  Kooij 《Ground water》1982,20(3):298-302

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Theoretical organic geochemistry. I. The thermodynamic stability of several cholestane isomers calculated by molecular mechanics     

Ger van Graas  Jan M.A. Baas  B. van de Graaf  J.W. de Leeuw 《Geochimica et cosmochimica acta》1982,46(11):2399-2402

The thermodynamic stabilities of thirteen cholestane isomers have been computed using molecular mechanics. The calculated composition of a mixture of these isomers at thermodynamic equilibrium is in agreement with the composition of a cholestane isomerate. From the calculated stabilities the extent to which isomerisation reactions can proceed during maturation can be predicted. The GLC retention order on non-polar phases of 20R/S isomeric pairs has been estimated from the preferred geometries of the molecules which are also obtained by molecular mechanics.  相似文献   

Stratigraphy,pollen analysis,and paleoclimatic interpretation of Pulbeena Swamp,northwestern Tasmania     

E.A. Colhoun  G. van de Geer  W.G. Mook 《Quaternary Research》1982,18(1):108-126

Sedimentary, palynologic, and ¹⁴C analysis of 480 cm of freshwater marl and swamp-peat deposits, formed under the influence of fluctuating artesian springs, provides a paleoenvironmental and paleoclimatic record of approximately 65,000 yr for northwestern Tasmania.The Holocene (Pollen Zone 1, 11,000-0 yr B.P.) climate was warm and moist, and forest vegetation was dominant throughout the area. During the later part of the last glacial stage (Pollen Zone 2, 35,000–11,000 yr B.P.) the climate was generally drier, and grassy open environments were widespread. The driest part of this period occurred between 25,000 to 11,000 yr B.P., when temperatures in western Tasmania were markedly reduced during the last major phase of glaciation. Prior to 35,000 yr B.P. (Pollen Zones 3–9) a long “interstadial complex” dating to the middle of the last glacial stage is recognized. During this period the climate was generally moist, and forest and scrub communities were more important than during the later part of the last glacial stage, except during Pollen Zone 5 when high Gramineae plus Compositae values suggest drier conditions. High Gramineae and Compositae values also occur in Pollen Zone 10 at the base of the diagram. They suggest that a phase of drier and cooler climatic conditions occurred during the early part of the last glacial stage.  相似文献   

Instrumental Neutron Activation Analysis Of 37 Geochemical Reference Samples     

H.A. van der  SLOOT J. ZONDERHUIS 《Geostandards and Geoanalytical Research》1979,3(2):185-193

37 geochemical reference samples, issued mostly by the U.S. Geological Survey and the "Centre de Recherches Pétrographiques et Géochi-miques", have been analysed for more than twenty trace elements using instrumental neutron activation technique. The results are compared with published data; in most oases, the agreement is good.  相似文献