Pockforms: an evaluation of pockmark-like seabed features on the Landes Plateau, Bay of Biscay   总被引：1，自引：1，他引：0  

Jorge Iglesias  Gemma Ercilla  Soledad García-Gil  Alan G. Judd 《Geo-Marine Letters》2010,30(3-4):207-219

Pockmark-like seabed features located on the Landes Plateau, Bay of Biscay, are depressions up to 1 km across and 50 m deep according to multibeam echo sounder data. Seismic (airgun and TOPAS) profiles show that each feature comprises a stack of identical features which extend down to 300 ms (twt). Three types of depressions, elongate, irregular and circular, appear as non-truncating V-shaped features in the Plio-Quaternary sediments. These features are located above the Parentis Basin where deep faults, basement ridges and diapiric bodies extend upwards across the sedimentary cover, providing ideal migration pathways for any buoyant fluids. Initial inspection suggests that these are classic pockmarks; however, the absence of reflection truncation and the absence of indications of shallow gas beneath the features indicate that they were not formed by the removal of sediment. These are “pockforms” but not “pockmarks”. This paper presents an explanation for the formation of these features, involving collapse and subsidence, sedimentary erosion, and only in some cases the erosion of seabed sediments by probable escaping fluids. These origins are mainly conducted through tectonic fluid dynamics which acted in the area up to the Late Miocene. It might be expected that these features would have been infilled by subsequent sedimentation, but their shape has been preserved because sedimentation in the area mainly comprised muds deposited from low-energy transportation (diluted gravity flows) and settling from hemipelagic suspension.  相似文献   

Characterization of bedform morphology generated under combined flows and currents using wavelet analysis     

Yovanni A. Cataño-Lopera  Jorge D. Abad  Marcelo H. García 《Ocean Engineering》2009,36(9-10):617-632

The wavelet transform (WT) has been successfully implemented in many fields such as signal and image processing, communication theory, optics, numerical analysis, and fluid mechanics. However, the application of WT to describe bedform morphology in coastal areas, oceans, and rivers is rare. The present study demonstrates the capability of WT analysis to fully represent the space–frequency characteristics of signals describing bed topography generated in marine and river environments. In this study WT is used to examine the morphological characteristics of bedforms generated in two separate laboratory facilities: a wave tank and a meandering channel. In the wave tank a set of ripples superimposed upon large wave ripples were generated; while in the meandering channel, 2D and 3D migrating ripples and dunes were observed. The WT proved to be a useful tool in detecting the complex variability of the generated bedform structures. The size distribution of the bottom features such as ripples, large wave ripples and sandbars were first examined along a 2D bed profile. Later analysis studied the variability of features in the transverse direction by using the power Hovmöller. Experiments in the wave tank were conducted for a mobility number of ψ=(10, 28), and a Reynolds wave number of R_ew=(17,500, 83,500) which correspond to waves alone (WA) and to combined flow (CF) scenarios, respectively. Experiments in the meandering channel were conducted under a morphological regime that produced mainly migrating sandbars.  相似文献   

The dimensional character of permeability: Dimensionless groups that govern Darcy's flow in anisotropic porous media     

Iván Alhama  Encarnación Martínez-Moreno  Gonzalo García-Ros 《国际地质力学数值与分析法杂志》2023,47(1):129-141

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