Oceanographic processes and morphosedimentary products along the Iberian margins: A new multidisciplinary approach

Postprin

Structure of mud volcano systems and pockmarks in the region of the Ceuta Contourite Depositional System (Western Alboran Sea): from episodic focused to diffuse flow

New high-resolution seismic and swath bathymetry data reveal the detailed structure of nine mud volcanoes and two large fields of pockmarks at water depths of 400–1100 m in the western Alborán Sea. These features are related to episodes of focused fluid flow through Pliocene-Quaternary contourite deposits of the Ceuta Drift. We describe nine mud volcano systems, composed of two key structural elements: (i) extrusive edifices comprising cones, bicones and low-dip mudflows interfingering with adjacent drift sediments and (ii) intrusive feeder complexes comprising pipes and unstratified downward-tapering cones underlying the extrusive edifices. The mud volcano systems are grouped into four types: I: Complex edifices; II: Stacked single edifices; III: Single edifices fed by buried bicones and IV: Single edifices. All except the last record episodic extrusive activity since the Pliocene, the timing of which is constrained by correlation between the main mud extrusion episodes and dated unconformities within the Ceuta Drift. Complex mud volcanoes composed of twin to multiple seabed cones are the longest-lived systems, with at least six extrusive episodes since the mid-Pliocene; most of the mud volcanoes appear to have been reactivated in the mid-Pleistocene (~ 0.9 Ma, MPR discontinuity) and all at MIS12 (0.4 Ma). While the onset of focused fluid flow was triggered by mid-Pliocene tectonically-driven diapirism of Lower Miocene shales that form the rooting zone of the mud volcanoes, we suggest that some of the Pleistocene phases of mud extrusion might be related to erosion of the contourite drift during major sea-level falls. In addition to vertical focused fluid flow, we propose that leakages from the mud volcano feeder complexes into high-permeability contourite sediments may cause lateral fluid migration and form gas accumulations. Lateral fluid flow in the near surface sediments could be responsible of forming subsurface reservoirs and consequently, random pockmarks by fluidification and/or liquefaction of the non-consolidated shallow sediments. Stacked buried paleo-pockmarks indicate that this mechanism has been persistent along recent times, at least after the mid-Pleistocene.

Current-controlled evidence on the sedimentation of the Alboran Sea in the Pliocene and Quaternary. Palaeoceanographic implications

A seismic analysis of the Pliocene and Quaternary stratigraphy was conducted in the Alboran Sea (westernmost Mediterranean) using more than 1250 profiles consisting of single- and multi-channel seismic records. This allowed for the updating and renaming of the stratigraphic boundaries and the establishment of a new Pliocene and Quaternary seismic stratigraphy for the Alboran Sea, after the relocation of the base of the Quaternary from 1.8 to 2.6 Ma. The boundaries of the stratigraphic division are as follows: the Messinian (M at 5.96 to 5.33 Ma), the intra-lower Pliocene (P0 at ca. 4.5 Ma), the top of the Zanclean (P1 at ca.3.3 Ma), the base of the Quaternary (BQD at ca. 2.6 Ma), the top of the Gelasian (Q0 at ca. 1.8 Ma), the intra-lower Quaternary (Q1 at ca. 1.12 Ma), and the top of the Calabrian (Q2 at ca. 0.7 Ma). Additionally, for the first time, the seismic analysis allowed us to present and discuss the evidence of contourite features reaching the scale of the Alboran Basin. Contourite drifts (plastered, sheeted, elongated separated and confined monticular drifts) and erosive features (terraces, scarps, moats and channels) were developed under the continuous influence of Mediterranean water masses (light and dense), after the opening of the Strait of Gibraltar in the latest Miocene (5.46 Ma). There are at least two primary factors controlling the contourite features, based on the seismic analysis, as follows: i) tectonics, which has governed the relocation of the main Mediterranean flow pathways and their circulation patterns; and ii) climate, which has influenced both water mass conditions (interfaces) and hinterland sediment sources, conditioning the morpho-seismic expression and growth pattern of the drifts and terrace formation (dimensions). The distribution of contourite features through time and space has allowed us to propose the three following main scenarios for ocean circulation since the opening of the Strait of Gibraltar: Atlantic Zanclean flooding; the Pliocene sea, with two different stages for the dense circulation; and the Quaternary sea, with well-defined and stable interfaces for the Atlantic Waters (AW), light and dense Mediterranean waters

Significance of bottom currents in deep-sea morphodynamics: an example from the Alboran Sea

We present an interdisciplinary study of the geomorphology, sedimentology and physical oceanography of the Alboran Sea (south-western Mediterranean Sea) to evaluate the potential role of bottom currents in shaping the Spanish and Moroccan continental margins and adjacent basins. Bathymetric and seismic data have allowed the recognition of the contourite deposits, including depositional (plastered, sheeted, channel-related, mounded confined, elongated and separated drifts), erosive (moats, channels and furrows) and mixed (terraces and scarps) features. Hydrographic data offer new insights into the distribution of the Mediterranean water masses, and reveal that bottom circulation of the Western Intermediate Water (WIW) and the Levantine Intermediate Water (LIW) interact with the Spanish slope, and the Western Mediterranean Deep Water (WMDW) on the Moroccan slope, Spanish base-of-slope and deep basins. The integration of distinct datasets and approaches allows a proposal of a new sedimentary model for the Alboran Sea that details the significance of bottom current processes in shaping deep-sea morphology. This model considers the bottom circulation of water masses governs physiography, that interface positions of water-masses with contrasting densities sculpt terraces on a regional scale, and that the morphologic obstacles play an essential role in the local control of processes and water-mass distributions. Our findings demonstrate the pivotal role of bottom water circulation in seafloor shaping and sedimentary stacking patterns for continental margins, establishing a new outlook for future studies of deep marine sedimentation

Structure, Dynamics, and Phase Behavior of Water in TiO2 Nanopores

Mesoporous titania is a highly studied material due to its energy and environment-related applications, which depend on its tailored surface and electronic properties. Understanding the behavior of water in titania pores is a central issue for practical purposes in photocatalysis, solar cells, bone implants, or optical sensors. In particular, the mechanisms of capillary condensation of water in titania mesopores and the organization and mobility of water as a function of pore filling fraction are not yet known. In this work, molecular dynamics simulations of water confined in TiO2-rutile pores of diameters 1.3, 2.8, and 5.1 nm were carried out at various water contents. Water density and diffusion coefficients were obtained as a function of the distance from the surface. The proximity to the interface affects density and diffusivity within a distance of around 10 Å from the walls, beyond which all properties tend to converge. The densities of the confined liquid in the 2.8 and the 5.1 nm pores decrease, respectively, 7% and 4% with respect to bulk water. This decrease causes the water translational mobility in the center of the 2.8 nm pore to be appreciably larger than in bulk. Capillary condensation takes place in equilibrium for a filling of 71% in the 2.8 nm pore and in conditions of high supersaturation in the 5.1 nm pore, at a filling of 65%. In the former case, the surface density increases uniformly with filling until condensation, whereas in the larger nanopore, a cluster of water molecules develops on a localized spot on the surface for fillings just below the transition. No phase transition is detected in the smaller pore. For all the systems studied, the first monolayer of water is strongly immobilized on the interface, thus reducing the accessible or effective diameter of the pore by around 0.6 nm. As a consequence, the behavior of water in these pores turns out to be comparable to its behavior in less hydrophilic pores of smaller size.Fil: Gonzalez Solveyra, Estefania. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Inorgánica, Analítica y Quimica Fisica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía; ArgentinaFil: de la Llave, Ezequiel Pablo. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Inorgánica, Analítica y Quimica Fisica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía; ArgentinaFil: Molinero, Valeria. University of Utah; Estados UnidosFil: Soler Illia, Galo Juan de Avila Arturo. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Inorgánica, Analítica y Quimica Fisica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía; Argentina. Comision Nacional de Energia Atomica. Centro Atomico Constituyentes; ArgentinaFil: Scherlis Perel, Damian Ariel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de Los Materiales, Medioambiente y Energía; Argentina. Universidad de Buenos Aires; Argentin

Sorption Isotherms of Water in Nanopores: Relationship Between Hydropohobicity, Adsorption Pressure, and Hysteresis

The motivation of this study is to elucidate how the condensation and desorption pressures in water sorption isotherms depend on the contact angle. This question is investigated for cylindrical pores of 2.8 nm diameter by means of molecular dynamics simulations in the grand canonical ensemble, in combination with the mW coarse-grained model for water. The contact angle is characterized for different sets of water–surface interactions. First, we show that desorption in open-ended pores with moderate or low water affinity, with contact angles greater or equal than 24°, is a nonactivated process in which pressure is accurately described by the Kelvin equation. Then, we explore the influence of hydrophobicity on the capillary condensation and on the width of the hysteresis loop. We find that a small increase in the contact angle may have a significant impact on the surface density and consequently on the nucleation free energy barrier. This produces a separation of the adsorption and desorption branches, exacerbating the emerging hysteresis. These results suggest that the contact angle is not as relevant as the adsorption energy in determining condensation pressure and hysteresis. Finally, we consider nonequilibrium desorption in pores with no open ends and describe how homogeneous and heterogeneous cavitation mechanisms depend on hydrophilicity.Fil: Factorovich, Matias Hector. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; ArgentinaFil: Gonzalez Solveyra, Estefania. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; ArgentinaFil: Molinero, Valeria. University of Utah; Estados UnidosFil: Scherlis Perel, Damian Ariel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; Argentin