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961.
Cristián Rodrigo Antonio González-Fernández Emilio Vera 《Marine Geophysical Researches》2009,30(1):1-19
Multichannel seismic reflection data recorded between Arauco Gulf (37°S) and Valdivia (40°S), on the Chilean continental margin,
were processed and modeled to obtain seismic images and sub-surface models, in order to characterize the variability of the
bottom-simulating reflector (BSR), which is a geophysical marker for the presence of gas hydrates. The BSR is discontinuous
and interrupted by submarine valleys, canyons, as well as by faults or fractures. The BSR occurrence is more common south
of Mocha Island due to moderate slopes and greater organic matter contribution by rivers in that area. Tectonic uplift and
structural instability change the stability gas hydrate zone and consequently the BSR position, creating in some cases missing
or double BSRs. Our modeling supports the presence of gas hydrate above the BSR and free gas below it. Higher BSR amplitudes
support higher hydrate or free gas concentrations. In the study area, gas hydrate concentration is low (an average of 3.5%)
suggesting disseminated gas hydrate distribution within the sediments. Also higher BSR amplitudes are associated with thrust
faults in the accretionary prism, which serve as conduits for gas flow from deeper levels. This extra gas supply produces
a wider thickness of gas hydrates or free gas. 相似文献
962.
Caterina Panzeca Aaron J. Beck Antonio Tovar-Sanchez Jose Segovia-Zavala Gordon T. Taylor Christopher J. Gobler Sergio A. Saudo-Wilhelmy 《Estuarine, Coastal and Shelf Science》2009,85(2):223-230
Distributions of dissolved vitamin B12 and total dissolved Co were measured to gain an understanding of the cycling of these interdependent micronutrients in six marine settings including; an upwelling location, a semi-enclosed bay, two urban coastal systems, and two open ocean locations. Along the coast of Baja California, Mexico, concentrations of B12 and dissolved Co varied from 0.2 to 11 pM and 180 to 990 pM, respectively. At a nearby upwelling station, vitamin B12 and Co concentrations ranged from 0.3 to 7.0 pM and 22 to 145 pM, and concentrations did not correlate with upwelling intensity. Concentrations of B12 were highest within Todos Santos Bay, a semi-enclosed bay off the coast of Baja California, Mexico, during a dinoflagellate bloom, ranging from 2 to 61 pM, while Co concentrations varied between 61 and 194 pM. In the anthropogenically impacted Long Island Sound, NY, U.S.A., B12 levels were between 0.1 and 23 pM and Co concentrations varied from 60 to 1900 pM. However, anthropogenic inputs were not evident in B12 levels in the San Pedro Basin, located outside Los Angeles, Ca, U.S.A., where concentrations of B12 were 0.2–1.8 pM, approximating observed open ocean B12 concentrations. In the Southern Ocean and North Atlantic Ocean, B12 levels were 0.4–4 pM and 0.2–2 pM, respectively. Total Co concentrations in the Southern Ocean and North Atlantic tended to be low; measuring 26–59 pM and 15–80 pM, respectively. These low Co concentrations may limit B12 synthesis and its availability to B12-requiring phytoplankton because the total dissolved Co pool is not necessarily entirely bioavailable. 相似文献
963.
Recent research in spatial real estate hedonic analysis 总被引:2,自引:2,他引:0
Antonio Páez 《Journal of Geographical Systems》2009,11(4):311-316
964.
965.
This paper presents MEPBAY and SMC software tools that allow comprehending and solving problems in headland-bay beach through a parabolic model. These tools can be employed as coastal engineering design tools (including nourishment designs) and also for academic purposes. They are oriented to different end-users, including coastal technicians, scientists and undergraduates and as coastal engineering design tools, they can be applied to different operational levels (pre-design and design). The aim of the paper is to present design guidelines, the capabilities of the tools, their potential use and applications. Both tools were applied to analyze San Lorenzo Beach and demonstrate their ability at different project levels. 相似文献
966.
This paper aims to quantify the uncertainty in the application of the Parabolic Bay Shape Equation (PBSE) for a bay in static equilibrium. By means of expert elicitation, a database was generated consisting of the position of the control points that determine the Static Equilibrium Planform (SEP). The elicitation consisted of two parts. In Part 1, 22 expert volunteers were asked to place the three control points that determine the SEP on a vertical aerial photograph of Taquaras–Taquarinhas Bay, a morphologically stable bay in the south of Brazil, approximately 1800 m in width and with an indentation of 750 m. The distribution of the location of the SEP along four evenly spaced (200 m) profiles in the southern part of the bay was determined. The overall bias of the location of the SEP calculated over the four profiles was in the order of 41 m (landward) and the average standard deviation was 116 m. These parameters increased when moving alongshore toward the curved section of the bay. This means that the uncertainty in the application of the PBSE is dependent on the particular point of interest along the bay. In Part 2 of the elicitation, 30 volunteers participated. This time the consequence of the placement of the control points (the corresponding SEP) was visible. Comparing the results from Parts 1 and 2, it was observed that when volunteers were directly confronted with the result of the placement of the control points (a plotted SEP) a much smaller variation in the position of the SEP occurred. This implies that when feedback on the result is provided the PBSE is a more robust method. 相似文献
967.
Mario González-Escobar Francisco Suárez-Vidal José Antonio Hernández-Pérez Arturo Martín-Barajas 《Geo-Marine Letters》2010,30(6):575-584
This study examines the structural characteristics of the northern Gulf of California by processing and interpreting ca. 415 km of two-dimensional multi-channel seismic reflection lines (data property of Petróleos Mexicanos PEMEX) collected in the vicinity of the border between the Wagner and Consag basins. The two basins appear to be a link between the Delfín Superior Basin to the south, and the Cerro Prieto Basin to the north in the Mexicali-Imperial Valley along the Pacific–North America plate boundary. The seismic data are consistent with existing knowledge of four main structures (master faults) in the region, i.e., the Percebo, Santa María, Consag Sur, and Wagner Sur faults. The Wagner and Consag basins are delimited to the east by the Wagner Sur Fault, and to the west by the Consag Sur Fault. The Percebo Fault borders the western margin of the modern Wagner Basin depocenter, and is oriented N10°W, dipping (on average) ~40° to the northeast. The trace of the Santa María Fault located in the Wagner Basin strikes N19°W, dipping ~40° to the west. The Consag Sur Fault is oriented N14°W, and dips ~42° to the east over a distance of 21 km. To the east of the study area, the Wagner Sur Fault almost parallels the Consag Sur Fault over a distance of ~86 km, and is oriented N10°W with an average dip of 59° to the east. Moreover, the data provide new evidence that the Wagner Fault is discontinuous between the two basins, and that its structure is more complex than previously reported. A structural high separates the northern Consag Basin from the southern Wagner Basin, comprising several secondary faults oriented NE oblique to the main faults of N–S direction. These could represent a zone of accommodation, or transfer zone, where extension could be transferred from the Wagner to the Consag Basin, or vice versa. This area shows no acoustic basement and/or intrusive body, which is consistent with existing gravimetric and magnetic data for the region. 相似文献
968.
Anderson H. Melo Peryclys R. O. Andrade Antonio J. C. Magalhães Daniel G. C. Fragoso Francisco P. Lima-Filho 《Basin Research》2020,32(5):1054-1080
Five 3rd-order depositional sequences are interpreted from the early Albian to late Campanian interval in the Potiguar Basin. An integrated analysis of seismic interpretations, well logs, cores and biostratigraphic data provides a stratigraphic framework composed by stratigraphic surfaces, systems tracts and sequences. Depositional Sequence 1 and 2 are, respectively, Albian and early to mid-Cenomanian aged and are composed by the falling stage, low stand, transgressive and high stand systems tracts. Depositional Sequence 3 is late Cenomanian to mid-Turonian aged and is composed by the transgressive and high stand systems tracts. Depositional sequences 4 and 5 are, respectively, late Turonian to mid-Santonian and late Santonian to mid-Campanian aged and are composed only by transgressive and high stand systems tracts. The lack of falling stage and low stand systems tracts in depositional sequences 3, 4 and 5, as well the increasing in transgressive and highstand systems tracts thickness as depositional sequences get younger, are reflection of an overall transgressive trend of a 2nd-order sequence. The interpretation proposed in this paper correlates onshore with offshore deposits within a seismic scale (3rd-order) sequence stratigraphy framework. This approach allows a better understanding of the Açu Formation, the primary oil-bearing formation of the Potiguar Basin. The Açu Formation is part of depositional sequences 1, 2 and 3 and is characterized by lateral and vertical variations of depositional systems instead of being associated to a specific depositional system. This sequence stratigraphy analysis can be used as a low-resolution framework for future high-resolution (4th-order scale) studies. 相似文献
969.
V. G. Veloso G. Neves M. Lozano A. Perez-Hurtado C. G. Gago F. Hortas & F. Garcia Garcia 《Marine Ecology》2008,29(S1):126-133
Demands for public outdoor recreation and urbanization are a potential source of environmental disturbances, particularly on sandy beaches. These habitats have therefore experienced rapid degradation worldwide. Talitrid amphipods, which are common inhabitants of sandy beaches, are probably good indicators of such disturbances. In this study, we evaluated the responses of the two amphipods Talitrus saltator and Atlantorchestoidea brasiliensis to human pressure on Spanish and a Brazilian beach, hypothesizing that disregarding species differences, their population sizes will decline under urbanized conditions. The Barra da Tijuca (Brazil) and Levante (Spain) beaches have mixed landscapes with varying levels of development, and each has a protected area (MPA) adjacent to urbanized sites. Numbers of talitrids as well as visitors were compared among sites on each beach. Talitrids were most abundant at the protected sites. This was true of both beaches, even though temporal patterns of human activity were quite different, with Levante experiencing sharp declines in the number of visitors during its harsh winter. Urbanized sites did not experience high Talitrid densities even during a period of low human pressure. On this basis, T. saltator and A. brasiliensis were considered good indicators of urbanization and recreational activities on sandy beaches. MPAs were found to be very important for the successful conservation of the talitrid populations. A feasible method of managing human pressure and thereby conserving beach biodiversity therefore seems to be the establishment of beach MPAs. 相似文献
970.
The aim was to evaluate the antioxidant defences and the occurrence of oxidative damage in Posidonia oceanica under a stress situation due to the epiphytism of the invasive macroalgae Lophocladia lallemandii. P. oceanica leaves were collected in the absence (control station) and in the presence of the epiphytic algae L. lallemandii and the antioxidant enzyme activities, markers of oxidative damage, and hydrogen peroxide production were determined. Antioxidant enzyme - catalase, glutathione peroxidase and superoxide dismutase - activities were significantly higher in Posidonia epiphytized by L. lallemandii. Malondialdehyde, protein carbonyl derivates, and glutathione levels were also higher in L. lallemandii epiphytized P. oceanica leaves compared to control samples. The production of hydrogen peroxide was also significantly increased when Posidonia was epiphytized by L. lallemandii. The invasion of P. oceanica meadows by L. lallemandii appeared to induce oxidative stress in the seagrass as evidenced by increased levels of oxidative stress markers and antioxidant defences. 相似文献