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91.
92.
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.
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.

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.

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.

- Salars Punta Negra , . 430 , . - -- — -- . , , . Salars , 550–750 . .
  相似文献   
93.
Although concentrations of polychlorinated biphenyls (PCBs) in biota, sediment and water of the Mediterranean Sea have been determined, most available data are for samples collected within the narrow coastal zone at relatively few locations. PCB concentrations in samples from the open Mediterranean Sea have not previously been reported. We report here the concentrations of PCBs in surface and sub-surface water from 36 locations. Analysis of our data indicate that there may be some correlation between PCB concentration in Mediterranean seawater and certain demographic and oceanographic features of the region.  相似文献   
94.
95.
In the Kivu lake region, the faults of the rift are concentrated in three netting following three main directions NE-SW, N-S and NW-SE. Some small tectonics trenchs. aligned along these three directions are intersecting in a zone lengthening in the N-S direction and 100–200 km wide. It does not look as if there was a chronological and regular succession in the coming out of faults belonging to a netting defined by a certain direction with regard to the faults of another netting; for, on the occasion of short tectonics events (eruptions, earthquakes), it is noticeable than any of these three nettings, are reactivated.  相似文献   
96.
97.
Core A179-15 from the southern North Atlantic exhibits one of the best paleoclimatic records for the last 25,000 years. This is because it is a high-sedimentation rate core and because it has been analysed at 1 cm intervals by Ericson and Wollin. The core has been used by Mörner for global climatic correlations. The magnetic measurements show a fairly drastic declination excursion at 12,350 B.P., i.e. exactly at the same age as the end of the Gothenburg Magnetic “Flip”. Therefore, the declination excursion in core A179-15 probably represents the end of the Gothenburg Magnetic “Flip” and Excursion. The excursion and a lithologic boundary verify the chronology earlier applied by Mörner.  相似文献   
98.
This paper describes the results of numerical experiments with a three-dimensional hydrodynamic and mud transport model in which sediment–fluid interaction is taken into account through the effects of hindered settling, buoyancy destruction in the turbulence k– model and sediment-induced barocline pressure gradients in the momentum equations. The model was applied to a schematic case representing a coastal area with a tidal river, navigation channel and harbour basin, and a real-world case, viz. Rotterdam harbour area in The Netherlands. The results show that the sediment transport into the harbour area, and subsequent siltation rates, increase by a factor 3 to 5 due to the sediment–fluid interaction. It is shown that the larger contribution stems from an increase in vertical gradients in suspended sediment.Responsible Editor: Jens Kappenberg  相似文献   
99.
Summary The orange cathodoluminescence (CL) of calcite is known to be due to the presence of Mn2+ cations. It has been demonstrated here using CL and electron paramagnetic resonance (EPR) crossed analysis from synthetic calcite that neither Fe2+ nor Fe3+ ions influence this luminescence emission. More complex natural calcium carbonates have been investigated to check whether or not this conclusion can be applied to them. For this purpose, different white marbles from Greek quarries were analysed with CL. The data are completed with neutron activation analysis (NAA) for manganese and iron contents. Again it is shown that only manganese plays a role in the orange CL of these white marbles. This result provides an important clue in the wide field of provenance determination of calcium carbonate used in ancient art.Received February 19, 2002; revised version accepted October 22, 2002 Published online March 10, 2003  相似文献   
100.
This paper introduces a new hypothesis about the formation of circular moraine features (CMFs) on felsenmeer-covered plateaux of the Varanger Peninsula, northern Norway. CMFs and glacial lineations in the northwestern part of the Varanger Peninsula were mapped from aerial photographs. In two CMF-rich areas, Base œrro-Plateau and Båtsfjordfjellet, the CMFs were investigated during fieldwork. The aim was to investigate possible entrainment, transport and deposition mechanisms of the CMFs in connection to ice sheet properties.The CMFs were deposited in connection with a polythermal ice cover. During glaciations, the ice sheet was cold-based on the boulder field plateaux and warm-based in valleys, especially in ice drainage pathways towards fjords. The CMF material was probably entrained en masse, on the Varanger Peninsula, in transition zones between warm- and cold-based ice. The debris transport took place close to the ice base. During deglaciation, the debris formed dirt cones, slowing down the melting of underlying dead-ice blocks. As material slid down the margins of the cones, the typical CMF shape was formed.  相似文献   
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