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101.
Osborne Alfred R. Resio Donald T. Costa Andrea Ponce de León Sonia Chirivì Elisabetta 《Ocean Dynamics》2019,69(2):187-219
Ocean Dynamics - We analyze surface wave data taken in Currituck Sound, North Carolina, during a storm on 4 February 2002. Our focus is on the application of nonlinear Fourier analysis (NLFA)... 相似文献
102.
We conducted the first quantitative assessment of coral breakage along a gradient of diving activities in Hong Kong, the most densely populated city in southern China. A survey of six 1 × 25 m transects at seven sites revealed a total of 81 broken corals, among which 44% were branching, 44% plate-like and 12% massive. There were 3–19 broken colonies per site. At most study sites, the percentage of broken corals exceeded the recommended no-action threshold of 4%, suggesting that management intervention is justified. There was a significant positive correlation between the number of broken coral colonies and the number of divers visiting the site. The branching Acropora and the plate-like Montipora suffered from much higher frequency of damage than their relative abundance, raising the concern that the cumulative impact of such differential susceptibility to breakage may affect coral community composition. 相似文献
103.
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105.
We report on a 6‐year nearshore bathymetric dataset from the Danube Delta (Romanian Black Sea coast) that comprises 16 km of erosive, stable and accumulative low‐lying micro‐tidal beaches northward of Sf. Gheorghe arm mouth. Two to three two‐dimensional longshore sandbars exhibit a net multi‐annual cyclic (2.8–5.5 years) offshore migration (20–50 m yr?1) in a similar way to other coasts worldwide. Bar morphology and behavior on the sediment‐rich accretionary (dissipative) sector differ substantially from that on the erosive (intermediate) sector. Shoreface slope is the most important factor controlling sandbar number and behavior. It determines different wave‐breaking patterns in the surf zone, translated into different offshore sediment transport and bar zone widths along the study site. Additionally, sediment availability, as a result of the distance from the arm mouth and of the long‐term evolution of the coast, controls the sandbar volume variability. These are all ultimately reflected in the variations of sandbar migration rates and cycle periods. A non‐dimensional morpho‐sedimentary parameter is finally presented, which expresses the bar system change potential as offshore sediment transport potential across the bar zone. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
106.
Pravesh Debba Emmanuel J. M. Carranza Alfred Stein Freek D. van der Meer 《Mathematical Geosciences》2009,41(4):421-446
This paper describes a quantitative methodology for deriving optimal exploration target zones based on a probabilistic mineral
prospectivity map. The methodology is demonstrated in the Rodalquilar mineral district in Spain. A subset of known occurrences
of mineral deposits of the type sought was considered discovered and then used as training data, and a map of distances to
faults/fractures and three band ratio images of hyperspectral data were used as layers of spatial evidence in weights-of-evidence
(WofE) modeling of mineral prospectivity in the study area. A derived posterior probability map of mineral deposit occurrence
showing non-violation of the conditional independence assumption and having the highest prediction rate was then put into
an objective function in simulated annealing in order to derive a set of optimal exploration focal points. Each optimal exploration
focal point represents a pixel or location within a circular neighborhood of pixels with high posterior probability of mineral
deposit occurrence. Buffering of each optimal exploration focal point, based on proximity analysis, resulted in optimal exploration
target zones. Many of these target zones coincided spatially with at least one occurrence of mineral deposit of the type sought
in the subset of cross-validation (i.e., presumed undiscovered) mineral deposits of the type sought. The results of the study
showed the usefulness of the proposed methodology for objective delineation of optimal exploration target zones based on a
probabilistic mineral prospectivity map. 相似文献
107.
Precambrian crystalline basement in southern Mongolia as revealed by SHRIMP zircon dating 总被引:5,自引:0,他引:5
Antoine Demoux Alfred Kröner Dunyi Liu Gombosuren Badarch 《International Journal of Earth Sciences》2009,98(6):1365-1380
Single zircon ages determined by ion microprobe (SHRIMP II) for granitoid gneisses from the southern slope of the Baga Bogd
massif (Gobi-Altai, southern Mongolia) reveal several episodes of zircon growth, ranging from late Palaeoproterozoic to late
Cambrian. The oldest events are documented by a zircon crystallization age for a gneiss protolith at 1519 ± 11 Ma and by a
xenocrystic zircon from a dark grey augen-gneiss yielding an age of c. 1701 Ma. Discrete igneous events are recorded in granite-gneisses
with protolith emplacement ages of 983 ± 6, 956 ± 3 and 954 ± 8 Ma. These ages provide the first record of early Neoproterozoic
magmatic activity in this region. A much younger and discrete magmatic event is recorded by several dioritic to granitic orthogneisses
which are tectonically interlayered with the older gneisses and have protolith emplacement ages between 502 and 498 Ma. These
late Cambrian granitoids of calc-alkaline affinity are likely to have been emplaced along an active continental margin and
suggest that the Baga Bogd Precambrian crustal fragment was either docked against the southward (present-day coordinates)
growing margin of the CAOB or was a large enough crustal entity to develop an arc along its margin. We speculate that the
Precambrian gneisses of this massif may be part of a crustal fragment rifted off the Tarim Craton. 相似文献
108.
Geodynamic evolution of Central Asia in the Paleozoic and Mesozoic 总被引:18,自引:0,他引:18
Wenjiao Xiao Alfred Kröner Brian Windley 《International Journal of Earth Sciences》2009,98(6):1185-1188
109.
Viggo Hansen Niels Nielsen Ruth Helkiær Jensen Kaf Hansen Kaj Hansen Johannes Krüger 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2013,113(1):91-100
Christensen, Leif: Faststående og omlejrede Saale-morånelersaflejringer. Et eksempel fra Szdding-området, Vestjylland. Geografisk Tidsskrift 82: 91–94. Copenhagen, Dec. 1, 1982. In situ clayey till materials on the Skovbjerg Bakkea, western Jutland can be recognized by crop-marks revealing pseudomorphs of ice-wedge polygons in orthogonal, random orthogonal and hexagonal patterns. The tills inside these polygonal patterns have high shear-strength values as measured by vane tests. Remoulded fossil solifluction deposits of till origin reveal stripes and deformed polygonal patterns in the crops. High strength as measured by vane are encountered below fossil solifluction deposits 4 meters below ground. 相似文献
110.
Niels Nielsen Viggo Hansen Kaj Hansen Kr. M. Jensen Sten Folving Sofus Christiansen 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2013,113(1):101-118
Meyer, Marlene: Settlement Patterns and Land-use in Northern Ghana—A Study of the Changes during the period 1963–1991 based on Historical Surveys and recent SPOT-images. Geografisk Tidsskrift 92:101–104. Copenhagen 1992. A study by Hunter (1966) describes how large areas along the Red Volta River bank, have been abandoned due to river blindness. The mapping of current land-use status and settlements patterns, using multispectral SPOT-satellite images, shows how the border of settlements continue to retreat, whereas new land is being reclaimed for bush fields in the abandoned areas. 相似文献