Search results for "BED"

Structural control on the presence and character of calas: Observations from Balearic Islands limestones rock coast macroforms

2013

Calas are characteristic embayed rocky coastline landforms related to steep-sided drowned valleys that were deeply incised during low sea-level stages into carbonate plateaus. This paper studies the factors that control the presence and character of calas in three different islands of the Balearic Archipelago (Mallorca, Menorca and Formentera) by means of Digital Elevation Model (DEM) reconstructions, embayment and catchment morphometric analysis and through the compilation of fault and joint orientations. All islands exhibit emerged carbonate platforms (Upper Miocene in age) characterised by horizontal or very gently-dipping bedding. Two distinct patterns observed at all study sites are th…

Growth processes, dimensional parameters and scaling relationships of two conjugate sets of compactive shear bands in porous carbonate grainstones, F…

2012

Abstract Three main sets of deformation bands are identified in the Lower Pleistocene carbonate grainstones of Favignana Island (Italy). A bedding-parallel set is interpreted to contain compaction bands, based on the lack of evidence for shear. The other two sets are oriented at a high-angle to bedding, forming a conjugate pair comprised of compactive strike-slip shear bands. In this study, we focus on the compactive shear bands documenting their development, as well as analyzing their dimensional parameters and scaling relationships. Single compactive shear bands are thin, tabular zones with porosity less than the surrounding host rocks, and have thicknesses and displacements on the order …

Detailed subglacial topography and drumlins at the marginal zone of Múlajökull outlet glacier, central Iceland: Evidence from low frequency GPR data

2016

Abstract New ground penetrating radar (GPR) observations on the Mulajokull surge-type outlet glacier, central Iceland, are presented. Overall 10.5 km of GPR profile lines were recorded parallel to the glacier margin in August, 2015. Detailed GPR investigations combined with high-accuracy GPS measurements allowed to build a high-resolution model of the subglacial topography. We provide new evidence of streamlined ridges beneath Mulajokull’s marginal zone interpreted as drumlins and show the location of the upper edge of the drumlin field. This discovery improves understanding of the location, morphology and development of drumlins as other geophysical observations of subglacial bedforms bene…

Local bedrock material in the glacigenic deposits as indicator of glaciotectonic deformation in Western Latvia

2012

Erosion and stabilisation sequences in relation to base level changes in the El Cautivo badlands, SE Spain

2008

Abstract The complex multiple-age badlands at El Cautivo are cut in upper Miocene marls of the uplifted and dissected Tabernas Basin, Almeria, in semi-arid SE Spain. Previous work identified six episodes of erosion and subsequent stabilisation, with ages ranging from the late Pleistocene to the present day. This paper uses newly-acquired digital elevation models, orthorectified aerial photographs, and field survey data to illustrate the development sequence of a series of gullies which drain into the Rambla de Tabernas. Changing drainage directions and phases of incision and stabilisation are related to the filling and subsequent dissection of the Tabernas lower lake sediments, differential…

Discussion on 'Estimating depth-averaged velocities in rough channels'

2002

In this short communication the four estimate criteria of the depth-averaged local velocity proposed by Byrd et al. (Earth Surface Processes and Landforms, 2000, Vol. 25, pp. 167-173) are compared both with the three-point method of Bathurst and with the average velocity obtained by integrating the velocity profile (FPa2) suggested by Ferro and Pecoraro (Water Resources Research, 2000, vol. 36, pp. 2761-2770). The comparison was carried out using 84 velocity profiles measured by an acoustic Doppler velocimeter in a rectangular flume with a gravel bed. Copyright © 2002 John Wiley and Sons, Ltd.

Seismo-stratigraphic model of “La Bandita” area in the Palermo Plain (Sicily, Italy) through HVSR inversion constrained by stratigraphic data

2018

Ambient noise Horizontal-to-Vertical Spectral Ratio (HVSR) technique is commonly used approach to obtain 1D models of the shear-wave velocity in the shallow surface of an investigated area. However, obtained models can have a wide margin of uncertainty if inversions have not been appropriately constrained by detailed stratigraphic information. An application of HVSR inversion constrained by lithostratigraphic data is presented in order to verify the effectiveness of this technique for purposes of geological and geophysical reconstruction of a sedimentary basin in a densely urbanized area. This is often the case of seismic microzonation studies, in which almost all the information derives fr…

Sedimentological and geoarchaeological evidence of multiple tsunamigenic imprint on the Bay of Palairos-Pogonia (Akarnania, NW Greece)

2010

Abstract This paper presents evidence of multiple tsunami impact on the Bay of Palairos-Pogonia, NW Greece, during the Holocene based on detailed geo-scientific studies. Altogether, 41 vibracores were drilled to detect high-energy influence in the stratigraphical record. Layers of coarse-grained allochthonous marine deposits were found intersecting autochthonous fine-grained back beach sediments in the Palairos coastal plain, on top of beach or marly bedrock units at Pogonia beach and along the Pogonia cliff section. High-energy deposits are associated with specific sedimentary structures such as fining upward sequences, rip up-clasts, basal erosional contact, bi- to multimodal grain size d…

Des particules charbonneuses, t�moins des variations de l'�rosion chimique d'un bassin versant calcaire durant l'holoc�ne (bassin de chaillexon, doub…

1999

Matter fluxes result from chemical and mechanical weathering that vary as a function of climate, relief, lithology and human activities. The aim of this paper is to characterize chemical weathering variations in the past using coaly particles found in both the geological substratum and the Holocene lacustrine sediments of a calcareous basin (Chaillexon lake, Doubs, France). Results point out that chemical weathering was the predominant erosional process in the watershed, which may be due to the calcareous nature of the bedrock. The significant variability of this process relative to mechanical weathering during the Holocene period can be interpreted as a consequence of the development of th…

Application of field portable EDXRF spectrometry to analysis of pigments of Levantine rock art

2010

The results of the analyses of elemental composition of red and black pigments of Levantine rock art from La Saltadora rock shelters (Valltorta gorge, Castellon, Spain) are presented in this paper. Nondestructive analyses were carried out using a portable energy dispersive X-ray fluorescence (EDXRF) spectrometer developed for in situ analysis. The results revealed the strong presence of calcium in all the analyzed locations due to the contribution of the underlying calcareous bedrock and the overlying crust. Iron is the main element detected in red pigments and manganese in black pigments. Iron and calcium ratios have been found indicative of the degree of preservation of the pictorial laye…