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61.
Pier Paolo G. Bruno Giuseppe Cippitelli Antonio Rapolla 《Journal of Volcanology and Geothermal Research》1998,84(3-4)
Fifteen seismic reflection lines from AGIP surveys, in and around the Campanian Plain and Mt. Somma–Vesuvius (south Italy) have been interpreted. The attention has been focused to the horizon pertinent to the top of the Mesozoic carbonate sequence and the Quaternary faults dissecting it. As a matter of fact, both are very important elements for understanding the origin of the volcanic activity in the area, that often in the past, has been the topic of debates not supported by reliable data. In the study area, referring to the depth of the carbonate basement, comparison between the result achieved by the seismic prospecting and previous gravity studies has been made. It shows coherence in some areas but large discrepancy within others. Near the town of S. Anastasia, the gravity and seismic depth estimates differ as much as 1000 m or more. Furthermore, the seismic data show that the source of the greatest volcanic eruption in the area (the so-called ‘Campanian Ignimbrite') is probably not located in the Acerra depression, as suggested by other authors. A main NE–SW fault directed toward Vesuvius, considered as playing a primary role on volcanogenetic processes and previously recognised only offshore by marine seismic survey, has been now identified also inland using this new seismic information. The results presented here strengthen the hypothesis that Mt. Vesuvius is located at the crossing point of two regional Quaternary sets of fault heading NW–SE and NE–SW. 相似文献
62.
63.
Prof. Dr. Bruno Engels 《International Journal of Earth Sciences》1965,54(2):758-795
The basement of northern Nicaragua is still a great problem stratigraphically. Enclosed tuffits (mainly basic, partly also intermediate to acid) appear of importance for both petrology and sedimentology. Not in the least they are guide horizons for a more accurate mapping. The vast regional distribution, commonly proved yet, suggests that the composition of the basement is considerably uniform and it seems that they do not belong to different periods and formations. Structurally the region is exceedingly complicated. The folding direction as regards plication and overthrusts is mainly to the North, but partly also to the East. Probably the “Totogalpa formation” (fanglomerates, conglomerates and sandstones, mainly reddish) which follows disconformably over the basement, already indicated, belongs to the sequence of tertiary tuffites, agglomerates, lavas etc. as they conformably form a formation of uniform composition. The relation of basement to lower Cretaceous (marine Albian; “Metapan”), which follows immediately to the south, is less clear. The lower Cretacious shows intensive and complicated folding at Siuna and it appears almost unmetamorphosed (? basement in a wider sense). The marine sediments (upper Cretacious - Miocene) of South Nicaragua are orogenetically only slightly efected (folding direction to E-N). To the North follows a thick serie of Tertiary and Quarternary volcanites (initially mainly submarinal, later on continental). Together with the NW/SE lineaments (Nicaragua depression, lines of volcanoes, coast line in the SW etc.) also NS directed ones clearly appear (coastline in the East). This direction can be found e. g. in the “granite ridge of Susucayan” and the accompanying faults in the vicinity. These latter structures may have taken an active part in the development of the flexured border of the Nicaraguan depression NW of Managua. 相似文献
64.
Bruno Engels 《International Journal of Earth Sciences》1956,45(1):143-150
Zusammenfassung Einleitend wird auf die vielfältige Problematik des Hunsrückschiefers hingewiesen. Hinsichtlich der Petro-Fazies ergibt sich ein Vorwalten der feinsandigen Komponente mit einem Feldspaltgehalt von durchschnittlich 10–13%. Die. Ergebnisse spektroskopischer und autoradiographischer Untersuchungen werden mitgeteilt. Die Mächtigkeit scheint in der SE-Eifel am größten zu sein und zum SE-Rand des Schiefergebirges hin ständig abzunehmen. Die Bio-Fazies wird vor allem hinsichtlich der sehr häufigen Fress-Bauten und Kriechspuren von Würmern behandelt, welche ein reiches Bodenleben im Hunsrückschiefer-Meer beweisen. Die Ansicht, daß der Hunsrückschiefer hauptsächlich aus Sedimenten eines Flach- und Wattenmeeres besteht, wurde bestätigt. 相似文献
65.
Bruno Ribbat Wolfgang Roether Karl Otto Münnich 《Earth and Planetary Science Letters》1976,32(2):331-341
A14C balance for the Eastern Caribbean deep water indicates the average inflow of Atlantic water into the basin to be 2.3 × 105 m3/sec (±30%), or about 2–4 times the values estimated previously. The balance uses a model representation of the deep-water turnover, and is based on14C concentrations at a station in the Venezuelan Basin which average Δ14C= 89‰ below 800 m depth with a total range of only 9‰, as well as on a14C concentration of the Atlantic inflow of Δ14C= ?71%. as obtained from measurements outside the Antilles Arch. The turnover time of the basin water below 2500 m depth is 55 years, which corresponds to an average upwelling velocity at this depth of about 35 m/year. With such upwelling, the temperature profile below 1800 m (the depth of the sill determining the inflow of new water) requires a vertical eddy diffusivity of about 5 cm2/sec. The oxygen consumption, and silica and CO2 regeneration, rates below 2500 m depth are obtained as ?0.18, + 0.08, and + 0.2 μmole kg?1 yr?1, respectively. The CO2 regeneration has but a negligible effect on the14C balance. 相似文献
66.
Mauro Celussi Bruno Cataletto Serena Fonda Umani Paola Del Negro 《Deep Sea Research Part I: Oceanographic Research Papers》2009,56(12):2193-2205
The identification of bacterial community structure has led, since the beginning of the 1990s, to the idea that bacterioplankton populations are stratified in the water column and that diverse lineages with mostly unknown phenotypes dominate marine microbial communities. The diversity of depth-related assemblages is also reflected in their patterns of activities, as bacteria affiliated to different groups can express different activities in a given ecosystem. We analysed bacterial assemblages (DGGE fingerprinting) and their activities (prokaryotic carbon production, protease, phosphatase, chitinase, beta-glucosidase and lipase activities) in two areas in the Ross Sea, differing mainly in their productivity regime: two stations are located in the Terra Nova Bay polynya area (highly productive during summer) and two close to Cape Adare (low phytoplankton biomass and activity). At every station a pronounced stratification of bacterial assemblages was identified, highlighting epipelagic communities differing substantially from the mesopelagic and the bathypelagic communities. Multivariate analysis suggested that pressure and indirectly light-affected variables (i.e. oxygen and fluorescence) had a great effect on the bacterial communities outcompeting the possible influences of temperature and dissolved organic carbon concentration. Generally activities decreased with depth even though a signal of the Circumpolar Deep Water (CDW) at one of the northern stations corresponded to an increase in some of the degradative activities, generating some ‘hot spots’ in the profile. We also found that similar assemblages express similar metabolic requirements reflected in analogous patterns of activity (similar degradative potential and leucine uptake rate). Furthermore, the presence of eukaryotic chloroplasts’ 16S rDNA in deep samples highlighted how in some cases the dense surface-water formation (in this case High Salinity Shelf Water—HSSW) and downwelling can affect, at least for some phylotypes, the bacterial (16S rDNA based) community structure of the dark ocean. 相似文献
67.
Yves Lagabrielle Manuel Surez Jacques Malavieille Diego Morata Felipe Espinoza Ren C. Maury Bruno Scalabrino Luis Barbero Rita de la Cruz Eduardo Rossello Herv Bellon 《地学学报》2007,19(6):413-424
Recent field work and review of radiometric data obtained from Neogene lavas and plutonic rocks exposed in the Eastern Central Patagonian Cordillera (46–48ºS), which overlie subducted segments of the South Chile Ridge, suggest important Late Miocene to Pleistocene morphological changes in relation to base level variations and/or tectonic events. We present new field observations from a region south of Lago General Carrera‐Buenos Aires, between the main Cordillera and the Meseta del Lago Buenos Aires, demonstrating that normal faulting controlled valley incisions and occurred during lava emplacement at 5–4 Ma and after 3 Ma. We also show that the 12 Ma basaltic flows of the Meseta del Lago Buenos Aires (∼2000 m a.s.l.) have been subjected to deep incision, with younger lavas dated at 1.2 Ma partially filling the valleys. These incisions are thought to reflect progressive eastward tilting of the entire meseta. Our new observations, together with additional features from Central Patagonia, strongly suggest that tectonic events led to a regional widespread morphological change after 5 Ma. The coincidence in time and space between the subduction of segments of the South Chile Ridge at 6 and 3 Ma causing opening of a slab window, and strong base level variations in the studied area, suggests a cause‐and‐effect relationship. In Central Patagonia, compressional tectonics ended well before extensional events reported here. Causes of uplift and further extension are probably completely disconnected. The uplift is purely tectonic in origin and occurred prior to the subduction of the South Chile Ridge. Extension should be a consequence of this subduction. 相似文献
68.
Erosion of the southern Gold Coast beaches (SE Queensland, Australia) was exacerbated after the extension of the Tweed River training walls in the early 1960s. To achieve the objective of restoring and maintaining beach amenity, significant nourishment works have been undertaken in Coolangatta Bay over the past 30 years. Particularly, under the Tweed River Entrance Sand Bypassing Project (TRESBP) since 1995, a number of nourishment campaigns and the implementation of a permanent sand bypass system in 2001 have resulted in significant changes of Coolangatta Bay morphology. The present case study investigates the influence of both wave climate and nourishment works on the area extending from the updrift Snapper Rocks area to downdrift Kirra Beach. SWAN spectral wave model is implemented at Coolangatta Bay area and forced by the global wave model WW3 to estimate wave forcing and the potential natural longshore drift entering in Coolangatta. Specific transects extracted from accurate bathymetric surveys are used to investigate and quantify Coolangatta Bay sedimentation for the period 1987–2005. A network of Argus video stations provides high sample rate information on the shoreline evolution. Results show that, over the past 10 years, Coolangatta Bay has infilled rapidly. Sedimentation reached up to 6 m in some areas between 1995 and 2005, with beach width increasing by 200 m at Kirra Beach. Rapid seaward shoreline migration is consistent with the intense over-pumping of sand relative to the natural potential to move sand alongshore. The nourishment strategy used during this project has successfully delivered large amounts of sand to the southern Gold Coast embayment, although it has been up to now controversial from many community perspectives. The artificial sand bypassing process proved to be much more efficient than depositing the dredged sand in the nearshore area which requires a significant period of low energy condition in order for the deposited sediment to migrate shoreward and weld to the shore. This case study confirms that, when carefully undertaken, sand bypassing is a sustainable and flexible soft engineering approach which can work in concert with natural processes. 相似文献
69.
Taro Takahashi Stewart C. Sutherland Rik Wanninkhof Colm Sweeney Richard A. Feely David W. Chipman Burke Hales Gernot Friederich Francisco Chavez Christopher Sabine Andrew Watson Dorothee C.E. Bakker Ute Schuster Nicolas Metzl Hisayuki Yoshikawa-Inoue Masao Ishii Takashi Midorikawa Yukihiro Nojiri Arne Krtzinger Tobias Steinhoff Mario Hoppema Jon Olafsson Thorarinn S. Arnarson Bronte Tilbrook Truls Johannessen Are Olsen Richard Bellerby C.S. Wong Bruno Delille N.R. Bates Hein J.W. de Baar 《Deep Sea Research Part I: Oceanographic Research Papers》2009,56(11):2075-2076