Mixed layers and surface ducts

In this investigation, we showed that high salinity promoted by hydrothermal inputs, reducing conditions of sediments with high content in organic matter, and the occurrence of an appropriate clay mineral precursor provide a suitable framework for low-temperature illitization processes. We studied the sedimentary illitization process that occurs in carbonaceous sediments from a lake with saline waters (Sochagota Lake, Colombia) located at a tropical latitude. Water isotopic composition suggests that high salinity was produced by hydrothermal contribution. Materials accumulated in the Sochagota Lake’s southern entrance are organic matter-poor sediments that contain detrital kaolinite and quartz. On the other hand, materials formed at the central segment and near the lake exit (north portion) are enriched in organic matter and characterized by the crystallization of Fe-sulfides. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM), and energy dispersive X-ray spectrometry (EDX) data allowed for the identification of illite and illite-dioctahedral vermiculite mixed layers (I-DV), which are absent in the southern sediments. High humidity and temperate climate caused the formation of small-sized metastable intermediates of I-DV particles by the weathering of the source rocks in the Sochagota Lake Basin. These particles were deposited in the low-energy lake environments (middle and north part). The interaction of these sediments enriched in organic matter with the saline waters of the lake enriched in hydrothermal K caused a reducing environment that favored Fe mobilization processes and its incorporation to I-DV mixed layers that acted as mineral precursor for fast low temperature illitization, revealing that in geothermal areas clays in lakes favor a hydrothermal K uptake.

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Variations in mixed-layer illite/smectite diagenesis in the rift and post-rift sediments of the Jeanne d'Arc Basin, Grand Banks offshore Newfoundland, Canada

Canadian Journal of Earth Sciences ◽

10.1139/e04-004 ◽

2004 ◽

Vol 41 (4) ◽

pp. 401-429 ◽

Cited By ~ 12

Author(s):

Iftikhar A Abid ◽

Reinhard Hesse ◽

John D Harper

Keyword(s):

Mixed Layer ◽

Fine Fraction ◽

Upper Jurassic ◽

Grand Banks ◽

Depth Profiles ◽

Jeanne D'arc Basin ◽

Central Ridge ◽

Jeanne D'arc ◽

Layer I ◽

Mixed Layers

Mixed-layer illite/smectite (I/S) clays were analyzed from 22 deep exploration wells from the Jeanne d'Arc Basin on the Grand Banks offshore Newfoundland, the host of large commercial hydrocarbon accumulations discovered in the last two and a half decades. The fine fraction of the clays (<0.1 µm) consists mainly of mixed-layer I/S with minor amounts of kaolinite, illite, and chlorite. Smectite and (or) smectite-rich I/S clays were supplied to the Jeanne d'Arc Basin from Upper Jurassic to Tertiary times. Smectite-rich I/S clays occur only in shallow samples irrespective of geologic age. The proportion of illite in I/S mixed-layers, as well as the degree of ordering, increase with depth and temperature indicating that smectite-rich I/S clays have been progressively illitized in both rift and post-rift sediments of the Jeanne d'Arc Basin during burial. The transition from random to R1-ordered I/S occurs between subsurface depths of 1940 and 3720 m and crosses major stratigraphic boundaries. The transition from R1- to R3-ordered I/S generally occurs below 4000 m depth. Variable shapes of I/S depth profiles reflect the influence of temperature, fluid migration, subsidence history, basin structure, lithology, and salt diapirism on I/S diagenesis. Based on these variations, the basin can be subdivided into 4 regions with different illitization gradients. In the Southern Jeanne d'Ac Basin, advanced I/S diagenesis probably reflects uplift and denudation and (or) higher paleogeothermal gradients. Rapid increase of percent illite in I/S with depth in the Trans-Basinal Fault area is most likely controlled by upward flow of hot, K+-bearing fluids along faults. The migration of hydrocarbons probably followed the same pathways as the illitizing fluids. Delayed illitization in the Northern Jeanne d'Arc Basin and Central Ridge area reflects insufficient K+ supply because of a lack of detrital K-feldspar in the host sediment, the absence of faulting, and the presence of thick shale intervals. These findings show that I/S depth profiles may vary within the same sedimentary basin due to a variety of geological factors. Single wells generally cannot be considered representative for the basin as a whole.

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Parameterization of Mixed Layer Eddies. Part I: Theory and Diagnosis

Journal of Physical Oceanography ◽

10.1175/2007jpo3792.1 ◽

2008 ◽

Vol 38 (6) ◽

pp. 1145-1165 ◽

Cited By ~ 353

Author(s):

Baylor Fox-Kemper ◽

Raffaele Ferrari ◽

Robert Hallberg

Keyword(s):

Mixed Layer ◽

Mixed Layer Depth ◽

Baroclinic Instability ◽

Finite Amplitude ◽

Climate Impacts ◽

Surface Mixed Layer ◽

Rotation Rates ◽

Wide Range ◽

Horizontal Density Gradient ◽

Mixed Layers

Abstract Ageostrophic baroclinic instabilities develop within the surface mixed layer of the ocean at horizontal fronts and efficiently restratify the upper ocean. In this paper a parameterization for the restratification driven by finite-amplitude baroclinic instabilities of the mixed layer is proposed in terms of an overturning streamfunction that tilts isopycnals from the vertical to the horizontal. The streamfunction is proportional to the product of the horizontal density gradient, the mixed layer depth squared, and the inertial period. Hence restratification proceeds faster at strong fronts in deep mixed layers with a weak latitude dependence. In this paper the parameterization is theoretically motivated, confirmed to perform well for a wide range of mixed layer depths, rotation rates, and vertical and horizontal stratifications. It is shown to be superior to alternative extant parameterizations of baroclinic instability for the problem of mixed layer restratification. Two companion papers discuss the numerical implementation and the climate impacts of this parameterization.

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A New "1201" Mercury-Based Cuprate with HgCe Mixed Layers: The Oxide Hg0.4Ce0.5Cu0.1Sr2-xLaxCuO4+δ

Journal of Solid State Chemistry ◽

10.1006/jssc.1995.1225 ◽

1995 ◽

Vol 116 (2) ◽

pp. 347-354 ◽

Cited By ~ 4

Author(s):

A. Maignan ◽

C. Martin ◽

C. Michel ◽

M. Hervieu ◽

B. Raveau

Keyword(s):

Mixed Layers

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Interfacial rheology of mixed layers of food proteins and surfactants

Current Opinion in Colloid & Interface Science ◽

10.1016/j.cocis.2013.04.002 ◽

2013 ◽

Vol 18 (4) ◽

pp. 302-310 ◽

Cited By ~ 49

Author(s):

Abhijit Dan ◽

Georgi Gochev ◽

Jürgen Krägel ◽

Eugene V. Aksenenko ◽

Valentin B. Fainerman ◽

...

Keyword(s):

Interfacial Rheology ◽

Food Proteins ◽

Mixed Layers

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Salinity-induced mixed and barrier layers in the southwestern tropical Atlantic Ocean off the northeast of Brazil

Ocean Science ◽

10.5194/os-7-63-2011 ◽

2011 ◽

Vol 7 (1) ◽

pp. 63-73 ◽

Cited By ~ 6

Author(s):

M. Araujo ◽

C. Limongi ◽

J. Servain ◽

M. Silva ◽

F. S. Leite ◽

...

Keyword(s):

Barrier Layer ◽

Austral Summer ◽

Late Winter ◽

Brazilian Coast ◽

Tropical Atlantic ◽

Austral Winter ◽

Surface Salinity ◽

Barrier Layer Thickness ◽

Near Surface ◽

Mixed Layers

Abstract. High-resolution hydrographic observations of temperature and salinity are used to analyze the formation and distribution of isothermal depth (ZT), mixed depth (ZM) and barrier layer thickness (BLT) in a section of the southwestern Atlantic (0°30´ N–14°00´ S; 31°24´–41°48´ W), adjacent to the northeastern Brazilian coast. Analyzed data consists of 279 CTD casts acquired during two cruises under the Brazilian REVIZEE Program. One occurred in late austral winter (August–October 1995) and another in austral summer (January–April 1997). Oceanic observations are compared to numerical modeling results obtained from the French Mercator-Coriolis Program. Results indicate that the intrusion of subtropical Salinity Maximum Waters (SMW) is the major process contributing to the seasonal barrier layer formation. These waters are brought by the South Equatorial Current (SEC), from the subtropical region, into the western tropical Atlantic boundary. During late austral winter southeastern trade winds are more intense and ITCZ precipitations induce lower surface salinity values near the equator. During this period a 5–90 m thick BLT (median = 15 m) is observed and BLT > 30 m is restricted to latitudes higher than 8° S, where the intrusion of salty waters between 8°–12.3° S creates shallow mixed layers over deep (ZT ≥ 90 m) isothermal layers. During austral summer, shallow isothermal and mixed layers prevail, when northeasterly winds are predominant and evaporation overcomes precipitation, causing saltier waters at the surface/subsurface layers. During that period observed BLT varies from 5 to 70 m and presents thicker median value of 35 m, when comparing to the winter. Furthermore, BLT ≥ 30 m is observed not only in the southernmost part of the study area, as verified during late winter, but in the latitude range 2°–14° S, where near-surface salty waters are transported westward by the SEC flow. These results indicate that the inclusion of salinity dynamics and its variability are necessary for studying mixed and barrier layer behaviors in the tropical Atlantic, where ocean-atmosphere coupling is known to be stronger.

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Ultramicrosensors based on transition metal hexacyanoferrates for scanning electrochemical microscopy

Beilstein Journal of Nanotechnology ◽

10.3762/bjnano.4.72 ◽

2013 ◽

Vol 4 ◽

pp. 649-654 ◽

Cited By ~ 4

Author(s):

Maria A Komkova ◽

Angelika Holzinger ◽

Andreas Hartmann ◽

Alexei R Khokhlov ◽

Christine Kranz ◽

...

Keyword(s):

Hydrogen Peroxide ◽

Detection Limit ◽

Transition Metal ◽

Prussian Blue ◽

Electrochemical Deposition ◽

Mixed Layer ◽

Scanning Electrochemical Microscopy ◽

The Stability ◽

Mixed Layers ◽

Electrochemical Microscopy

We report here a way for improving the stability of ultramicroelectrodes (UME) based on hexacyanoferrate-modified metals for the detection of hydrogen peroxide. The most stable sensors were obtained by electrochemical deposition of six layers of hexacyanoferrates (HCF), more specifically, an alternating pattern of three layers of Prussian Blue and three layers of Ni–HCF. The microelectrodes modified with mixed layers were continuously monitored in 1 mM hydrogen peroxide and proved to be stable for more than 5 h under these conditions. The mixed layer microelectrodes exhibited a stability which is five times as high as the stability of conventional Prussian Blue-modified UMEs. The sensitivity of the mixed layer sensor was 0.32 A·M−1·cm−2, and the detection limit was 10 µM. The mixed layer-based UMEs were used as sensors in scanning electrochemical microscopy (SECM) experiments for imaging of hydrogen peroxide evolution.

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Oceanic wave-balanced surface fronts and filaments

Journal of Fluid Mechanics ◽

10.1017/jfm.2013.348 ◽

2013 ◽

Vol 730 ◽

pp. 464-490 ◽

Cited By ~ 40

Author(s):

James C. McWilliams ◽

Baylor Fox-Kemper

Keyword(s):

Mixed Layer ◽

Stokes Drift ◽

Surface Gravity Wave ◽

Initial Flow ◽

Coriolis Forces ◽

Flow Perturbation ◽

Front Shape ◽

Oceanic Wave ◽

Mixed Layers ◽

Layer Deformation

AbstractA geostrophic, hydrostatic, frontal or filamentary flow adjusts conservatively to accommodate a surface gravity wave field with wave-averaged, Stokes-drift vortex and Coriolis forces in an altered balanced state. In this altered state, the wave-balanced perturbations have an opposite cross-front symmetry to the original geostrophic state; e.g. the along-front flow perturbation is odd-symmetric about the frontal centre while the geostrophic flow is even-symmetric. The adjustment tends to make the flow scale closer to the deformation radius, and it induces a cross-front shape displacement in the opposite direction to the overturning effects of wave-aligned down-front and up-front winds. The ageostrophic, non-hydrostatic, adjusted flow may differ from the initial flow substantially, with velocity and buoyancy perturbations that extend over a larger and deeper region than the initial front and Stokes drift. The largest effect occurs for fronts that are wider than the mixed layer deformation radius and that fill about two-thirds of a well-mixed surface layer, with the Stokes drift spanning only the shallowest part of the mixed layer. For even deeper mixed layers, and especially for thinner or absent mixed layers, the wave-balanced adjustments are not as large.

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Clay Minerals Variations in Quaternary Sediments of Basrah City-Iraq

Earth Science Research ◽

10.5539/esr.v6n2p41 ◽

2017 ◽

Vol 6 (2) ◽

pp. 41

Author(s):

Mohanad Hamid Al-Jaberi

Keyword(s):

Clay Minerals ◽

Mineralogical Composition ◽

Silty Sand ◽

Recent Sediment ◽

Quaternary Sediments ◽

Marine Transgression ◽

Fine Grain ◽

Clayey Silt ◽

Marine Facies ◽

Mixed Layers

Mineralogical and chemical analysis of two well cutting in quaternary sediments at Basrah city. This study have been focused on the quaternary clay minerals variations which give a clear indication to marine transgression and or / regression in Hammar formation. Kaolinite, Illite, Palygoreskite, Illite-Palygorestike mixed layer, Chlorite, Montmorillonite, Vermiculte, and mixed layers of Illite- Smectite are the most quantitatively important phyllosilicates in soil studies in both boreholes. The mineralogical composition of cutting sediments shows significant variability in the different size fractions and depth distribution. Chlorite and kaolinite minerals were increase in the fine grain size especially in the clayey silt, whereas montmoriolllinite and vermiculite minerals were increase in coarse grains especially in silty sand texture. Kaolinite decrease in abundance with depth, which give indicative of a transition from non-marine in quaternary recent sediment ( fresh or brackish water silt) to marine facies in quaternary Hammar formation ( marine shelly silt) during last transgression of quaternary. Palygoreskite mineral percentages increasing at depths 27 and 28 meter , after decreased at 30, 32, 35 , and 40 m respectively , which give data indication that early quaternary marine transgression happened in 32m , and center of quaternary marine transgression detected in 27 and 28 meters , while late marine transgression detected in 17 m , and all of these represent by Hammar formation. Soil ageing also caused to downward increase of montmorillonite suggest to climate became more arid during the early quaternary. Variations ratio of montmorillonite versus kaolinite can be indicated to climatic fluctuation. Illite-Semectite featured indicates changes in both sediment source and paleoclimate. Illite transformation for Illite-Palygoreskite mixed layers with ageing. Vermiculite has strong susceptibility to increase with age. SiO₂, Al₂O₃, CaO, MgO, K₂O, and Fe₂O₃ were the major oxides that identified in present study and used as indicated of clay minerals in studied sediments.

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