Facies analysis was carried out on 21 selected cores from the Bannock area in order to investigate the relationships between sedimentation and tectonism. Bannock Basin is a large, > 3500 m (uncorrected) deep subcircular depression near the deformation front of the Mediterranean Ridge facing the Sirte Abyssal Plain. The basin is divided into several sub-basins aligned along a rim-syncline surrounding a central elevated area (salt dome?). High-density brines and anoxic sediments occupy the deepest part of the depressions.
The facies distribution is controlled by the bottom configuration in that pelagic facies typically occur on plateaus and domes, debris-flow deposits in base-of-slope settings, and turbidites in basinal settings. The facies distribution may therefore be used to reconstruct the evolution of the various parts of the rim-syncline.
Erosional gaps may be related to tectonism or may be features created by the passage of major turbiditic events.
The results of our study of the facies associations, and of the rates of sediment accumulation, indicate that the collapse of the eastern part of the rim-syncline pre-dates the collapse of the western part. The western basins are deeper and larger than the eastern ones and (unlike the latter) are aligned at the foot of a strike-slip fault with a vertical offset of at least 700 m. 相似文献
The natural river water reference material SLRS‐6 (NRC‐CNRC) is the newest batch of a quality control material routinely used in many international environmental laboratories. This work presents a nine‐laboratory compilation of measurements of major and trace element concentrations and their related uncertainties, unavailable in the NRC‐CNRC certificate (B, Cs, Li, Ga, Ge, Hf, Nb, P, Rb, Rh, Re, S, Sc, Se, Si, Sn, Th, Ti, Tl, W, Y, Y, Zr and REEs). Measurements were mostly made using inductively coupled plasma‐mass spectrometry. The results are compared with equivalent data for the last batch of the material, SLRS‐5, measured simultaneously with SLRS‐6 in this study. In general, very low concentrations, close to the quantification limits, were found in the new batch. The Sr isotopic ratio is also reported. 相似文献
The article discusses the development of the favela into a tourist attraction. Rocinha, Rio de Janeiro, is the paradigmatic “tourist favela”, with tours taking place regularly since the early 1990s and with three thousand tourists visiting the site each month. The development of the favela into a tourist destination is seen as part of the so-called reality tours phenomenon and of the global circulation of the favela as a trademark. The methodology included different strategies: long interviews with qualified informants, field observation, and participant observation in different tours. The article concludes with some thoughts on tourism activities in impoverished areas. 相似文献
Natural Hazards - Rockfalls represents a sudden, extremely important geomorphological hazard and may become a threat for people’s life, as well as goods and transport. The present study aims... 相似文献
The invertebrate benthic community of two Aveiro salt pond systems was studied in order to evaluate its diversity, density and the influence of organic matter and salt production. Samples were collected monthly at Esmolas and Tanoeiras. Five groups of benthic organisms were found: Nemathelminthes, Annelida (Nereis diversicolor), Crustacea (Sphaeroma serratum andTanais cavolini), Insecta (Chironomidae), Bivalvia Mollusca (Cerastoderma edule, Spisula solida andMya arenaria) and Gasteropoda Mollusca (Hydrobia ulvae, Cingulla cingullus, Cingulla semistriata, Odostomia rissoides, Odostomia unidentata, Scrobicularia alba, Valvata cristata andPaludestrina acuta). The highest density of the benthic community was observed during the non-productive season in all but the crystallizing pond systems. In both salt ponds, salinity acted as limiting factor. The dominant group was Gasteropoda, although high densities of Bivalvia were recorded in some ponds. In the feeder pond and the channels, species diversity was highest in the Tanoeiras salt pond, probably because its physical and chemical characteristics allowed the development of stable communities. 相似文献
Utilizing 20 days of current meter and sea level elevation records taken in two cross-sections in mid-Chesapeake Bay an objective interpolation procedure was devised to allow the computation of vertical profiles of the laterally integrated subtidal volume fluxes at each section, at 3-h intervals over the period of the experiment. The presence of a classical mean estuarine circulation was observed; however, departures from this gravitational circulation were revealed on a shorter time scale, reaching the value of 20 000 m3 s?1 over a day, and featuring behaviors of reverse estuarine, storage and discharge modes.The volume flux computations through each cross-section based on the measured current velocities, the freshwater inflow and the calculated Stokes transport were in agreement with each other. A two-layered box model of the mean subtidal circulation in the segment of the estuary bound by the two cross-sections is offered.A comparison was made between the computations of net volume flux into and out of the Bay above these sections using two independent methods: (1) the accounting of volume continuity based upon direct measurements of volume flux through the sections; and (2) the direct calculation of the time rate of change of volume of the upper Bay obtained from tide gauge records. The agreement between the two results was found to be very good. Further evidence is provided for the upward phase propagation of the oscillations in the residual motion of estuarine waters. 相似文献
Tree ring studies are usually used to determine or verify climatic factors prevailing at a given place or region that may cause tree-ring width variations. Few studies are dedicated to the solar phenomena which may underlie these tree-ring width variations. Furthermore, it is known that some terrestrial phenomena are influenced by short- and long-time scale solar variability. An optical and computational method was set up and applied to tree samples (Araucaria angustifolia from Santa Catarina State in Southern Brazil) in order to obtain a growth ring width mean chronology. Spectral analysis is used for the search of periodicities, by maximum entropy and iterative regression methods. The results evidenced several embedded signals at periods which may be related to solar activity variations. Cross-correlation analysis between sunspot number and tree-ring data was performed and a lag of zero year was obtained. From our work, it seems that the tropical conifer species Araucaria angustifolia may be a good choice for studies on Sun-Earth relationships and their regional effects. 相似文献
We have conducted observations with the aid of a seismo-tiltmeter station, which is based on the Ostrovsky pendulum and installed at the Geodynamic Observatory Cueva de los Verdes at Lanzarote Island since 1995. In this station the signal is separated into two frequency bands – tidal tilts (from 0 to 5 mHz) and ground oscillations in the frequency range of free Earths normal modes (from 0.2 to 5 mHz). The later band, called accelerometer channel, has additional amplification. We analyzed the background records in the frequency range of Earths free oscillations from August 2000 to September 2001, as well as, Earths normal modes after strong earthquakes. We found several distinctive persistent peaks in the spectra of background oscillations. Both amplitudes of distinguished peaks and noises have seasonal variations. We found that spectra of background oscillations are different in the frequency interval between 1.4 and 2.5 mHz for North- South and East-West components. 相似文献