Mass-transport deposits on Mediterranean continental margins

Extensive mass transport deposits and multiple slide scars testify widespread and recurrent submarine sediment failures occurring during the late Quaternary on the SW-Adriatic and SE-Sicilian margins. These mass movements and their consequences contributed to shape the continental slopes and fill the basins with characteristic signatures. Geomorphological, seismo-stratigraphic, sedimentological and biostratigraphic data provide clues to: 1) define distinct failure mechanisms investigating on factors that determine dissimilar organization of coeval displaced masses, 2) reconstruct successive phases of failure stressing on the same location where slide scars crosscut and mass-transport deposits overlap, 3) analyze regional setting and indicate the most suitable place where to calculate mass wasting frequency. Discussions on the role of fluid flow, currents activity and tectonic deformation determine a wider view on the construction of the studied continental margins.

Sedimentary and structural controls on seismogenic slumping within mass transport deposits from the Dead Sea basin

GIA acknowledges funding from the Carnegie Trust to undertake fieldwork for this project. SM acknowledges the Israel Science Foundation (ISF grant no. 1436/14) and the Ministry of National Infrastructures, Energy and Water Resources (grant no. #214-17-027). RW was supported by the Israel Science Foundation (ISF grant no. 1245/11). We thank Hugo Ortner and Pedro Alfaro for careful and constructive reviews.

Pleistocene Mass Transport Deposits Off Barbados Accretionary Prism (Lesser Antilles)

Two Pleistocene mass transport deposits (MTDs), with volumes of thousands of km(3), have been identified from multi-channel seismic data in the abyssal plain at the front of the Barbados accretionary prism. Estimated sediment volumes for these MTDs are likely underestimated due to limited seismic coverage. In this work, we suggest that these MTDs are comparable in size to large submarine landslides as reported in the literature. These MTDs lie on the vicinity of two major oceanic ridges, the Barracuda Ridge and the Tiburon Rise. It is also suggested in this work that the MTDs come from seismicity associated with the formation of the Barracuda Ridge or the Barbados accretionary prism; however, triggering mechanisms involved in their formation remain uncertain. The present study discusses the potential causal factors accounting for the formation of these MTDs.

Reactive mass transport modelling of a three-dimensional vertical fault zone with a finger-like convective flow regime

For a three-dimensional vertically-oriented fault zone, we consider the coupled effects of fluid flow, heat transfer and reactive mass transport, to investigate the patterns of fluid flow, temperature distribution, mineral alteration and chemically induced porosity changes. We show, analytically and numerically, that finger-like convection patterns can arise in a vertically-oriented fault zone. The onset and patterns of convective fluid flow are controlled by the Rayleigh number which is a function of the thermal properties of the fluid and the rock, the vertical temperature gradient, and the height and the permeability of the fault zone. Vigorous fluid flow causes low temperature gradients over a large region of the fault zone. In such a case, flow across lithological interfaces becomes the most important mechanism for the formation of sharp chemical reaction fronts. The degree of rock buffering, the extent and intensity of alteration, the alteration mineralogy and in some cases the formation of ore deposits are controlled by the magnitude of the flow velocity across these compositional interfaces in the rock. This indicates that alteration patterns along compositional boundaries in the rock may provide some insights into the convection pattern. The advective mass and heat exchanges between the fault zone and the wallrock depend on the permeability contrast between the fault zone and the wallrock. A high permeability contrast promotes focussed convective flow within the fault zone and diffusive exchange of heat and chemical reactants between the fault zone and the wallrock. However, a more gradual permeability change may lead to a regional-scale convective flow system where the flow pattern in the fault affects large-scale fluid flow, mass transport and chemical alteration in the wallrocks

Timing and emplacement dynamics of newly recognised mass flow deposits at ~ 8–12 ka offshore Soufrière Hills volcano, Montserrat : how submarine stratigraphy can complement subaerial eruption histories

This contribution describes two mass movement deposits (total volume ~0.5 km3) identified in seven marine cores located 8 to 15 km offshore southern Montserrat, West Indies. The deposits were emplaced in the last 35 ka and have not previously been recognised in either the subaerial or distal submarine records. Age constraints, provided by radiocarbon dating, show that an explosive volcanic eruption occurred at ca 8–12 ka, emplacing a primary eruption-related deposit that overlies a large (~0.3 km3) reworked bioclastic and volcaniclastic flow deposit, formed from a shelf collapse between 8 and 35 ka. The origin of these deposits has been deduced through the correlation of marine sediment cores, component analysis and geochemical analysis. The 8–12 ka primary volcanic deposit was likely derived from a highly-erosive pyroclastic flow from the Soufrière Hills volcano that entered the ocean and mixed with the water column forming a water-supported density current. Previous investigations of the eruption record suggested that there was a hiatus in activity at the Soufrière Hills volcano between 16 and 6 ka. The ca 8–12 ka eruptive episode identified here shows that this hiatus was shorter than previously hypothesised, and thus highlights the importance of obtaining an accurate and completemarine record of events offshore from volcanic islands and incorporating such data into eruption history reconstructions. Comparisons with the submarine deposit characteristics of the 2003 dome collapse also suggests that the ~8–12 ka eruptive episode was more explosive than eruptions from the current eruptive episode.

STUDY ON MASS-TRANSPORT IN EASTMAN-AQ POLYMER FILM BY USING NON-STEADY-STATE CHRONOAMPEROMETRY AT AN ULTRAMICRODISK ELECTRODE

Non-steady-state chronoamperometry of ultramicroelectrodes is a powerful method for the study of mass transport in polymer films. This method has many advantages over the conventional methods at a macroelectrode and the steady state method at an ultramicroelectrode, which yield the most information. The apparent diffusion coefficient, D(app), and the concentration of reactant in the film, c(f), can be determined from a single experiment without knowing the thickness of the film. We studied the transport of several species such as Ru(NH3)63+, Ru(bpy)3(2+), NR and MV2+ in Eastman-AQ polymer film coated ultramicroelectrodes by using this method.

Mud mass transport due to waves based on an empirical rheology model featured by hysteresis loop

A vertical 2-D water-mud numerical model is developed for estimating the rate of mud mass transport under wave action. A nonlinear semi-empirical rheology model featured by remarkable hysteresis loops in the relationships of the shear stress versus both the shear strain and the rate of shear strain of mud is applied to this water mud model. A logarithmic grid in the vertical direction is employed for numerical treatment, which increases the resolution of the flow in the neighborhood of both sides of the interface. Model verifications are given through comparisons between the calculated and the measured mud mass transport velocities as well as wave height changes. (C) 2006 Elsevier Ltd. All rights reserved.

Mass Transport In The Equatorial Indian Ocean

In the equatorial oceans, the meridional currents are far less energetic than their zonal counterparts. The response of the Equatorial Indian Ocean to the seasonal reversals in the zonal wind field. is quite interesting and unique. A modest attempt, considering the shortcomings in the hydrographic data availability and distribution, is made to evaluate the variability in the zonal transport of mass. in_ both space and time. The peculiarities in its hydrological regime imposed upon by the seasonally varying winds is best appreciated when compared with the quasi permanent circulation characteristics of the Pacific and Atlanti'c.The major features of the tequatorial mass transport is outlined in the introductory chapter of this thesis for the Pacific and Atlantic Mass transport studies in the Indian Ocean, as can be seen from the earlier studies, gis“ the least known and understood, though could have captured the attention of both the experimentalist and the theoretician alike. owing to its complexity. Since in the Indian Ocean, the studies on the zonal mass transport are limited and are confined to the equator only, an attempt has been made to compute the mass transport extending from 5 N to 20 S.

Mass transport effects in the borohydride oxidation reaction-Influence of the residence time on the reaction onset and faradaic efficiency

The borohydride oxidation reaction (BOR) was studied on Pt and Au electrodes by cyclic voltammetry in dilute alkaline borohydride solutions (0.1 M NaOH + 10(-3) mol L(-1) NaBH(4)). More specifically, the electrodes were considered as either Vulcan XC72-supported Pt or Au (noted as Pt/C and Au/C, respectively) active layers or smooth Pt or Au surfaces, the latter possibly being covered by a layer of (non-metalized) Vulcan XC72 carbon powder. The BOR onset potential and the number of electrons (n(e-)) exchanged per BH(4)(-) anion (faradaic efficiency) were investigated for these electrodes, to determine whether the residence time of reaction intermediates (at the electrode surface or inside the porous layer) does influence the overall reaction pathway/completion. For the carbon-supported platinum, n(e-) strongly depends on the thickness of the active layer. While thin (ca. 0.5 mu m-thick) Pt/C active layers yield n(e-) < 4, thick layers (approximately 3 mu m) yield n(e-)approximate to 8, which can be ascribed to the sufficient residence time of the molecules formed within the active layer (H(2), by heterogeneous hydrolysis, or BOR intermediates) enabling further (near-complete) oxidation. This puts into evidence that not only the nature of the electrocatalyst is important to reach high BOR efficiency, but also the structure/thickness of the active layer. The same trend applies for Au/C active layers and for smooth Pt or Au surfaces covered with a layer of (inactive) Vulcan XC72. In addition, the BOR onset usually shifts negative when the reaction intermediates are trapped, which suggests that some of the intermediates are more easily oxidized than BH(4)(-) itself; based on literature data, BH(3)OH(-) species is a likely candidate. (C) 2011 Elsevier B.V. All rights reserved.

Process-based modelling of mass transport in the subsurface

Modern societies rely on natural water pathways that include subsurface flow of water and dissolved chemicals. The thesis presents a range of numerical and analytical models for simulating physical, chemical and biological processes in the subsurface, including coastal aquifers, the near-surface vadose zone, and solute transport in biogeochemically active aquifers.