Search results for "Sediment"

Characterisation of sedimentary and petrophysical heterogeneities of a microporous reservoir : the case of Chalk (Upper Cretaceous, Paris Basin, Fran…

2016

Chalk is defined as a microporous reservoir rock. This formation is a prolific hydrocarbon-bearing reservoir in the North Sea and is one of the main aquifers in the Paris Basin. The heterogeneity of chalk in terms of petrophysical properties (both surface and subsurface) is illustrated by porosity ranging from 4 to 52 %, permeability from 0.01 to 100 mD, and P-wave velocity on water-saturated samples from 2.4 to 4.4 km.s-1 (Alam et al., 2011).In the study area (Normandie, France), taken as an outcrop analogue, 114 samples were collected (Cenomanian – Santonian). As in the North Sea fields, these samples show great petrophysical heterogeneity: total porosity () from 6.1 to 46.5 %, very low …

Distribution of rare earth elements in marine sediments from the Strait of Sicily (western Mediterranean Sea): Evidence of phosphogypsum waste contam…

2010

Concentrations of rare earth elements (REE), Y, Th and Sc were recently determined in marine sediments collected using a box corer along two onshore–offshore transects located in the Strait of Sicily (Mediterranean Sea). The REE + Y were enriched in offshore fine-grained sediments where clay minerals are abundant, whereas the REE + Y contents were lower in onshore coarse-grained sediments with high carbonate fractions. Considering this distribution trend, the onshore sediments in front of the southwestern Sicilian coast represent an anomaly with high REE + Y concentrations (mean value 163.4 lg g 1) associated to high Th concentrations (mean value 7.9 lg g 1). Plot of shale-normalized REE + …

Paleolimnological evidence of environmental changes in seven subtropical reservoirs based on metals, nutrients, and sedimentation rates

2021

Made available in DSpace on 2022-04-28T19:40:54Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-11-01 Paleolimnological research can shed light on a broad range of environmental concerns; however, such studies are scarce in reservoirs. To address this lack of knowledge, a paleolimnological investigation was conducted to determine historical changes in sedimentation rates (SR), using 210Pb geochronology, and concentrations of nutrients and metals (Cr, Cu, Ni, Pb, Zn, Al, Mn, Fe) in seven subtropical reservoirs (São Paulo, Brazil). Sediment cores were collected in the dam areas. Increasing SR was observed in all reservoirs and was mainly attributed to eutrophication and changes in land…

Sedimentation and Fouling of Optical Surfaces at the ANTARES Site

2003

ANTARES is a project leading towards the construction and deployment of a neutrino telescope in the deep Mediterranean Sea. The telescope will use an array of photomultiplier tubes to detect the Cherenkov light emitted by muons resulting from the interaction with matter of high energy neutrinos. In the vicinity of the deployment site the ANTARES collaboration has performed a series of in-situ measurements to study the change in light transmission through glass surfaces during immersions of several months. The average loss of light transmission is estimated to be only ~2% at the equator of a glass sphere one year after deployment. It decreases with increasing zenith angle, and tends to satur…

Phenomenological description of sedimentation in turbulent vortex tangles

2008

The aim of this Brief Report is to provide a simple intuitive derivation of the results for sedimentation velocity of a small spherical particle in a counterflow vortex tangle in turbulent superfluid. When the velocity of the tangle vortex lines is small as compared to that of the particle, our results reduce to those obtained previously by other authors through more complex arguments, except for a logarithmic dependence of one of the coefficients on the vortex line density. Comparison of both derivations may be useful to clarify the range of validity of the expressions for the forces between the particle and the tangle.

Electrokinetic Phenomena Revisited: A Lattice—Boltzmann Approach

2003

The Lattice-Boltzmann method (LBM) is an efficient tool to solve the Navier-Stokes equations. Based on this method we have developed a scheme to investigate electrokinetic phenomena in charged colloidal suspensions. The equations of motion that are solved are the so-called electrokinetic equations, i.e. a set of partial differential equations that couple the gradient of the electrostatic potential to the hydrodynamic flow by means of a mean field theory. These equations have been extensively used to study electroviscous phenomena for the limit of a weakly charged sphere in an unbounded electrolyte. We demonstrate that our method can be applied beyond these limit. As an example we discuss th…

Abrupt Alnus population decline at the end of the first millennium CE in Europe - The event ecology, possible causes and implications

2019

The study, based on the examination of 70 published and unpublished pollen profiles from Poland and supplementary data from the surrounding regions, shows that an abrupt, episodic Alnus population decline at the end of the first millennium CE was a much more widespread event than has been previously reported, spanning large areas of the temperate and boreal zones in Europe. The data from Poland suggest that the decline was roughly synchronous and most likely occurred between the 9th and 10th centuries, with strong indications for the 10th century. The pollen data indicate that human impacts were not a major factor in the event. Instead, we hypothesize that one or a series of abrupt climatic…

Sedimentological implications of an unusual form of the trace fossil Rhizocorallium from the Lower Muschelkalk (Middle Triassic), S. Poland

2011

Specimens of the trace fossil Rhizocorallium isp. with retrusive limbs occur in 10–20-cm-thick composite beds: the bottom layers contain abundant Planolites and Thalassinoides trace fossils, and the top layers are built of horizontally bedded pelitic limestone and contain less bioturbational structures. The first specimens of Rhizocorallium isp. occur just 2–3 cm above the lower surfaces of the top layers. The horizontal protrusive sections are 1 cm high and 1 cm wide. At some sites, the horizontal tunnels end, and the limbs become first obliquely retrusive (45°) at a distance of 1.5–2.5 cm, and then vertically retrusive at a distance of 4–6 cm, or at once vertically retrusive at a similar …

40 Ar/ 39 Ar ages of fallout tephra layers and volcaniclastic deposits in the sedimentary succession of the western Woodlark Basin, Papua New Guinea:…

2001

The structure of western Sicily, central Mediterranean

2002

Western Sicily is part of the Sicilian chain, a sector of the SE-verging Alpine orogenic belt in the central Mediterranean. Interpretation of seismic reflection profiles, boreholes and recent inland geological data, have enabled us to assess the deep structural grain. A wedge of flat-lying Mesozoic–Miocene carbonate and terrigenous rocks (pre-Panormide nappes) is superimposed on NW-trending, 7–8 km thick, Mesozoic–Paleogene carbonate thrust ramps (Trapanese units), arranged in two structural levels extending from the Tyrrhenian coast to western offshore Sicily. Upper Miocene to Pleistocene terrigenous strata, often deformed, fill syntectonic basins above the thrust pile. The main tectonic t…