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11.
Gabriela Dan Nabil Sultan Bruno Savoye Jacques Deverchere Karim Yelles 《International Journal of Earth Sciences》2009,98(4):769-789
The Algerian margin is a seismically active region, where during the last century, several large magnitude earthquakes took
place. This study combines geotechnical and sedimentological data with numerical modelling to quantitatively assess the present-day
slope stability of the Algerian margin. Geotechnical laboratory tests, such as cyclic triaxial tests, oedometric tests and
vane shear tests were carried out on sediment cores collected on the study area. The liquefaction potential of a sediment
column located about 30 km from the Boumerdès earthquake epicentre of 21st May 2003 was evaluated theoretically for an earthquake
of M
w
= 6.8. We show that thin sand and silt beds such as those described on recovered sediment cores are the main cause of sediment
deformation and liquefaction during earthquakes. Numerical calculations showed that the slope failure may occur during an
earthquake characterised by a PGA in excess of 0.1g, and also that, under a PGA of 0.2g liquefaction could be triggered in shallow silty–sandy deposits. Moreover, comparison of the predicted slope failure with
failure geometries inferred from seafloor morphology showed that earthquakes and subsequent mass movements could explain the
present-day morphology of the study area. 相似文献
12.
13.
Inversely graded turbidite sequences in the deep Mediterranean: a record of deposits from flood-generated turbidity currents? 总被引：2，自引：0，他引：2
Turbidity currents generated during floods of small and medium rivers have been demonstrated to be an important process of sediment transport from continent to abyss. They produce fine-grained turbidite deposits. No deposit related to these flood-related turbidity currents has yet been described in the deep sea. In this paper, we present some unusual sandy to muddy turbidite beds cored in the Var turbidite system (NW Mediterranean). They show a coarsening-upward basal unit capped with a classical fining-upward unit which are related to the periods of increasing and decreasing discharge at the river mouth, respectively. The two units are separated by a contact which can be gradational to erosional. This intrabed contact is interpreted as resulting from erosion during peak flood conditions. This intrabed contact can be confused with classical basal contacts of turbidite beds. The frequency of hyperpycnal turbidite beds can be used to relate climatic changes inland to the deep-sea sedimentary record, as an increase corresponds to periods of enhanced flooding at the river mouth. 相似文献
14.
15.
S. Assier-Rzadkieaicz P. Heinrich P. C. Sabatier B. Savoye J. F. Bourillet 《Pure and Applied Geophysics》2000,157(10):1707-1727
16.
Marine Geophysical Research - 相似文献
17.
The Golo Margin in eastern Corsica is dissected by four canyons and two gullies which fed turbidite systems. Study of the dispersal of surficial sediments and flow dynamic in the Golo system is based on Kullenberg and interface cores interpreted in relation to a previously published seismic dataset. Cores were described in detail and interpreted within a sedimentary and stratigraphic framework. During the last 42,000 years, gravity processes which occurred in the large systems with a canyon source were mainly slide-induced, differentiated turbulent surges and hyperpycnal flows. Processes occurring in the small system with a gully source are mainly hyperconcentrated and concentrated flows. Deposits from the Corsican Margin can intercalate with products of processes triggered on the Pianosa Ridge located in the eastern part of the basin. During relative sea-level lowstands or during periods of rapid or high-amplitude sea-level fall, only large canyons (South and North Golo) are supplied by carbonate-rich hyperconcentrated and concentrated flows which are channelled in incised valleys on the shelf. During periods of slow or low-amplitude sea-level fall and during sea-level rise, sediments are trapped on a shelf delta and intensely winnowed by shelf hydrodynamic processes. Sand-rich hyperconcentrated and concentrated flows occur. All the systems fed by a canyon are active simultaneously. Gullies form and are active only during periods of sea-level rise. During relative highstands of sea level (Holocene), all the system is draped by hemipelagic sediments. Relative sea-level changes and canyon location relative to river mouths have a strong influence on the nature of sediment input, and the initiation and type of gravity flows which, in turn, control morphology and geometry. 相似文献
18.
L.?Pichevin T.?MulderEmail author B.?Savoye A.?Gervais M.?Cremer D.?J.?W.?Piper 《Geo-Marine Letters》2003,23(2):117-124
New high-resolution seismic reflection data collected along the eastern margin of Corsica have been analysed to describe the morphology of the turbidite systems located seaward of the Golo River mouth. The boomer data reveal that there is not only one turbidite system directly associated with the river, but four additional, non-coalescing systems which grew simultaneously. In the south, the system has the typical morphology of a turbidite deposit rich in mud and sand with a well-developed meandering canyon and channel morphology. In the north, they have the morphology of sand-rich turbidite systems with shorter straight channels. The southernmost deposits are interpreted to represent a more advanced stage of turbidite system development. Terraces, recognised by their particular seismic facies on boomer profiles which clearly differs from the surrounding levee facies, are observed in the channel meanders. They are interpreted as confined levees built by vertical accretion due to deposition from low-energy flows. Despite limited penetration, boomer seismics are demonstrated to be a useful complement to lower-resolution sparker data. The boomer data are superior (1) for the characterisation of fine-grained turbidite deposits by extending seawards the limits of the turbidite systems commonly defined by the acoustic response of sands, (2) in demonstrating the persistence of turbiditic processes farther towards the basin, and (3) for proposing conceptual models for the formation of terraces in fan valleys. 相似文献
19.
Turbiditic levee deposition in response to climate changes: The Var Sedimentary Ridge (Ligurian Sea)
Stéphan J. Jorry Isabelle Jégou Laurent Emmanuel Ricardo Silva Jacinto Bruno Savoye 《Marine Geology》2011,279(1-4):148-161
The Var turbiditic system located in the Ligurian Sea (SE France) is an intermediate mud/sand-rich system. The particularity of the Var deep-sea fan is its single channel with abrupt bends and its asymmetric and hyper-developed levee on the right hand side: the Var Sedimentary Ridge. Long-term sediment accumulation on the Var Sedimentary Ridge makes this an ideal target for studying the link between onshore climate change and deep-sea turbidite stratigraphy. This paper focuses on the establishment of the first detailed stratigraphy of the levee, which is used to analyze the timing of overbank deposition throughout the last deglaciation. Main results indicate that high variability in turbidite frequencies and deposition rates along the Var Sedimentary Ridge are determined by two main parameters: 1) the progressive decrease of the levee height controlling the ability of turbidity currents to spill out from the channel onto the levee, and 2) climatic variations affecting the drainage basin, in particular changes in glacial condition since late Last Glacial Maximum to early Holocene. Compared to other deep-water areas, this study confirms the ability of turbiditic systems to record past climatic events on millennial timescales, and underlines the influence of European deglaciation on the observed decrease in turbidite activity in the Var canyon. The presence of a very narrow continental shelf and a single, large channel-levee system makes the Var Sedimentary Ridge a unique example of climate-controlled turbiditic accumulations. 相似文献
20.
K.O. Buesseler C.R. Benitez-Nelson S.B. Moran A. Burd M. Charette J.K. Cochran L. Coppola N.S. Fisher S.W. Fowler W.D. Gardner L.D. Guo
. Gustafsson C. Lamborg P. Masque J.C. Miquel U. Passow P.H. Santschi N. Savoye G. Stewart T. Trull 《Marine Chemistry》2006,100(3-4):213
Thorium-234 is increasingly used as a tracer of ocean particle flux, primarily as a means to estimate particulate organic carbon export from the surface ocean. This requires determination of both the 234Th activity distribution (in order to calculate 234Th fluxes) and an estimate of the C / 234Th ratio on sinking particles, to empirically derive C fluxes. In reviewing C / 234Th variability, results obtained using a single sampling method show the most predictable behavior. For example, in most studies that employ in situ pumps to collect size fractionated particles, C / 234Th either increases or is relatively invariant with increasing particle size (size classes > 1 to 100s μm). Observations also suggest that C / 234Th decreases with depth and can vary significantly between regions (highest in blooms of large diatoms and highly productive coastal settings). Comparisons of C fluxes derived from 234Th show good agreement with independent estimates of C flux, including mass balances of C and nutrients over appropriate space and time scales (within factors of 2–3). We recommend sampling for C / 234Th from a standard depth of 100 m, or at least one depth below the mixed layer using either large volume size fractionated filtration to capture the rarer large particles, or a sediment trap or other device to collect sinking particles. We also recommend collection of multiple 234Th profiles and C / 234Th samples during the course of longer observation periods to better sample temporal variations in both 234Th flux and the characteristic of sinking particles. We are encouraged by new technologies which are optimized to more reliably sample truly settling particles, and expect the utility of this tracer to increase, not just for upper ocean C fluxes but for other elements and processes deeper in the water column. 相似文献