Annotated record of the detailed examination of Mn deposits from the CLIMAX II (SCAN) Expedition stations aboard R/V Argo in the central North Pacific

A 0.25 m US Naval Electronics Lab box corer was used to take replicate samples from an oligotrophic bottom under the North Pacific Central Water Mass (approx. 28 degrees N, 155 degrees W). The bottom is a red clay with manganese nodules at a depth of 5500-5800 m. Macrofaunal density ranges from 84 to 160 individuals per m super(2) and is therefore much the same as in Northwest Atlantic Gyre waters. Of the macrofaunal taxa, polychaetes dominate (55 per cent), followed by tanaids (18 per cent), bivalves (7 per cent), and isopods (6 per cent). Meiofaunal taxa were only partially retained by the 297 micrometer screen used in washing. Even then, they are 1.5-3.9 times as abundant as the microfaunal taxa, with nematodes being numerically dominant by far. Foraminifera seem to comprise an important portion of the community, but could not be assessed accurately because of the inability to discriminate living and dead tests. Remains of what are probably xenophyophoridans are also very important, but offer the same problem. Faunal diversity is extremely high, with deposit feeders comprising the overwhelming majority. Most spp are rare, being encountered only once. The distributions of only 3 spp show any significant deviation from randomness. The polychaete fauna from box cores collected from 90 m to the north was not significantly different from that of the principal study locality. Concordance appeared at several taxonomic levels, from spp through microfaunal/ meiofaunal relationships. As a result, the variation in total animal abundance shows aggregation among cores. The authors discuss Sokolova's concept of a deep-sea oligotrophic zone dominated by suspension feeders, and reconcile it with our present findings. The high diversity of the fauna combined with the low food level contradict theories that relate diversity directly with productivity.

(Table 1, Page 1046-1047) Chemical composition of iron-manganese concretions from the Indian Ocean recovered by the R/V Vityaz and the R/V Ob

The data given in this and previous communications is insufficient to assess the quantitative role of these supplementary sources in the Indian Ocean, but they do not rule out their local significance. Elucidation of this problem requires further data on the characteristics of the composition and structure of nodules in various different metallogenic regions of the ocean floor. A study of the distribution of ore elements in nodules both depthwise and over the area of the floor together with compilation of the first schematic maps based on the results of analyses of samples from 54 stations) enables us to give a more precise empirical relation between the Mn, Fe, Ni, Cu, and Co contents in Indian Ocean nodules, the manganese ratio and the values of the oxidation potential, which vary regularly with depth. This in turn also enables us to confirm that formation of nodules completes the prolonged process of deposition of ore components from ocean waters, and the complex physico-chemical transformations of sediments in the bottom layer. Microprobe investigation of ore rinds revealed the nonuniform distribution of a num¬ber of elements within them, owing to the capacity of particles of hydrated oxides of manganese and iron to adsorb various elements. High concentration of individual elements is correlated with local sectors of the ore rinds, in which the presence of todorokite, in particular, has been noted. The appearance of this mineral apparently requires elevated Ca, Mg, Na, and K concentrations, because the stable crystalline phase of this specific mineral form of the psilomelane group may be formed when these cations are incorporated into a lattice of the delta-MnO2 type.

Annotated record of the detailed examination of Mn deposits from R/V Eltanin Cruise 5 stations

Cores, submarine photography and dredges described in this report were taken during the R/V Eltanin Cruise 5 in 1962 by the Department of Geology, Florida State University. Cores and dredges were recovered for 31 stations and are available at the Antarctic Research Facility, Florida State University for sampling and study.

Age of bottom sediments from the South Atlantic Rise as indicated by 14C data for stations of R/V Professor Shtokman

Sedimentation of pelagic biogenic coccolithic-foraminiferal sediments predominates in the section of the South Atlantic ridge between 20° and 30°S. Sedimentation rate and thickness of Late Quaternary sediments differ in the rift valley, the crestal section of the ridge, its flanks and transform faults. Holocene and layers representing the most recent and pen¬ultimate continental glaciations and the last interglacial are distinguishable in the late Quaternary profile. During their development, changes in the mean annual sea surface temperature in the tropical zone of the South Atlantic were minimal, i.e. 1-2°C.

Annotated record of the detailed examination of Mn deposits in the Atlantic Ocean from cruises from R/V Atlantis II, R/V Knorr, R/V Melvin and R/V James M. Gilliss in 1980-1981

This report is Volume 3 of Descriptions of WHOI rock dredge samples. This series represents a major effort to catalog the rock dredge samples in the WHOI Sea Floor samples collection, and to disseminate this information throughout the scientific community. Volume 3 contains sample descriptions and station data for the dredge stations from five cruises during the period September 1978 through December 1980. The material in this and subsequent volumes of rock descriptions was largely prepared onboard ship by the participating scientists. Volume 3 was printed prior to volumes 1 and 2 because of the excellent documentation of the samples represented in this volume.

Antarctic free-air and complete Bouguer gravity anomaly grid

Gravity surveying is challenging in Antarctica because of its hostile environment and inaccessibility. Nevertheless, many ground-based, airborne and shipborne gravity campaigns have been completed by the geophysical and geodetic communities since the 1980s. We present the first modern Antarctic-wide gravity data compilation derived from 13 million data points covering an area of 10 million km**2, which corresponds to 73% coverage of the continent. The remove-compute-restore technique was applied for gridding, which facilitated levelling of the different gravity datasets with respect to an Earth Gravity Model derived from satellite data alone. The resulting free-air and Bouguer gravity anomaly grids of 10 km resolution are publicly available. These grids will enable new high-resolution combined Earth Gravity Models to be derived and represent a major step forward towards solving the geodetic polar data gap problem. They provide a new tool to investigate continental-scale lithospheric structure and geological evolution of Antarctica.

Magnetic extracts of three gravity cores located at the Ceará Rise, the Mid-Atlantic Ridge and the Sierra Leone Rise

The magnetic microparticle and nanoparticle inventories of marine sediments from equatorial Atlantic sites were investigated by scanning and transmission electron microscopy to classify all present detrital and authigenic magnetic mineral species and to investigate their regional distribution, origin, transport, and preservation. This information is used to establish source-to-sink relations and to constrain environmental magnetic proxy interpretations for this area. Magnetic extracts were prepared from sediments of three supralysoclinal open ocean gravity cores located at the Ceará Rise (GeoB 1523-1; 3°49.9'N/41°37.3'W), the Mid-Atlantic Ridge (GeoB 4313-2; 4°02.8'N/33°26.3'W), and the Sierra Leone Rise (GeoB 2910-1; 4°50.7'N/21°03.2'W). Sediments from two depths corresponding to marine isotope stages 4 and 5.5 were processed. This selection represents glacial and interglacial conditions of sedimentation for the western, central, and eastern equatorial Atlantic and avoids interferences from subsurface and anoxic processes. Crystallographic, elemental, morphological, and granulometric data of more than 2000 magnetic particles were collected by scanning and transmission electron microscopy. On basis of these properties, nine particle classes could be defined: detrital magnetite, titanomagnetite (fragmental and euhedral), titanomagnetite-hemoilmentite intergrowths, silicates with magnetic inclusions, microcrystalline hematite, magnetite spherules, bacterial magnetite, goethite needles, and nanoparticle clusters. Each class can be associated with fluvial, eolian, subaeric, and submarine volcanic, biogenic, or chemogenic sources. Large-scale sedimentation patterns are delineated as well: detrital magnetite is typical of Amazon discharge, fragmental titanomagnetite is a submarine weathering product of mid-ocean ridge basalts, and titanomagnetite-hemoilmenite intergrowths are common magnetic particles in West African dust. This clear regionalization underlines that magnetic petrology is an excellent indicator of source-to-sink relations. Hematite encrustations, magnetic spherules, and nanoparticle clusters were found at all investigated sites, while bacterial magnetite and authigenic hematite were only detected at the more oxic western site. At the eastern site, surface pits and crevices were seen on the crystal faces indicating subtle early diagenetic reductive dissolution. It was observed that paleoclimatic signatures of magnetogranulometric parameters such as the ratio of anhysteretic and isothermal remanent magnetizations can be formed either by mixing of multiple sources with separate, relatively narrow grain size ranges (western site) or by variable sorting of a single source with a broad grain size distribution (eastern site). Hematite, goethite, and possibly ferrihydrite nanoparticles occur in all sediment cores studied and have either high-coercive or superparamagnetic properties depending on their partly ultrafine grain sizes. These two magnetic fractions are generally discussed as separate fractions, but we suggest that they could actually be genetically linked.

(Table 1) Heat flow measurements in the Central Pacific during Cruise 48 of R/V Vityaz

Eight measurements of heat flow in the Pacific floor were made during Cruise 48 of R/V Vityaz; four on the Manihiki Plateau, three - on the Marcus-Necker Rise, and one - in the Hawaiian Trough. Higher than average heat flows, up to 3.2 HFU, were recorded on submarine uplifts.

Annotated record of the detailed examination of Mn deposits from R/V Tokaidaigaku Maru II Cruise GDP-1 stations

The present paper, deals with the results of the bottom sampling. Sampling devices were a gravity corer for heat flow measurement and dredges of bucket type.

Annotated record of the detailed examination of Mn deposits from the R/V Argo ZETES Expedition in the Pacific Ocean

The cores and dredges described are taken during the R/V Argo ZETES Expedition from March until August 1966 by the Scripps Institute of Oceanography. A total of 53 cores and dredges were recovered and are available at Scripps Institute of Oceanography for sampling and study.

Gravity collapse structures in the Central Precordillera fold-andthrust belt, Argentina

Several landforms found in the fold-and-thrust belt area of Central Precordillera, Pre-Andes of Argentina, which were often associated with tectonic efforts, are in fact related to non-tectonic processes or gravitational superficial structures. These second-order structures, interpreted as gravitational collapse structures, have developed in the western flank of sierras de La Dehesa and Talacasto. These include rock-slides, rock falls, wrinkle folds, slip sheets and flaps, among others; which together constitute a monoclinal fold dipping between 30º and 60º to the west. Gravity collapse structures are parallel to the regional strike of the Sierra de la Dehesa and are placed in Ordovician limestones and dolomites. Their sloping towards the west, the presence of bed planes, fractures and joints; and the lithology (limestone interbedded with incompetent argillaceous banks) would have favored their occurrence. Movement of the detached structures has been controlled by lithology characteristics, as well as by bedding and joints. Detachment and initial transport of gravity collapse structures and rockslides in the western flank of the Sierra de la Dehesa were tightly controlled by three structural elements: 1) sliding surfaces developed on parallel bedded strata when dipping >30° in the slope direction; 2) Joint’s sets constitute lateral and transverse traction cracks which release extensional stresses and 3) Discontinuities fragmenting sliding surfaces.  Some other factors that could be characterized as local (lithology, structure and topography) and as regional (high seismic activity and possibly wetter conditions during the postglacial period) were determining in favoring the steady loss of the western mountain side in the easternmost foothills of Central Precordillera.

Idealized modeling of the role of stability and shear on mesoscale gravity wave evolution

Mesoscale Gravity Waves (MGWs) are large pressure perturbations that form in the presence of a stable layer at the surface either behind Mesoscale Convective Systems (MCSs) in summer or over warm frontal surfaces behind elevated convection in winter. MGWs are associated with damaging winds, moderate to heavy precipitation, and occasional heat bursts at the surface. The forcing mechanism for MGWs in this study is hypothesized to be evaporative cooling occurring behind a convective line. This evaporatively-cooled air generates a downdraft that then depresses the surface-based stable layer and causes pressure decreases, strong wind speeds and MGW genesis. Using the Weather Research and Forecast Model (WRF) version 3.0, evaporative cooling is simulated using an imposed cold thermal. Sensitivity studies examine the response of MGW structure to different thermal and shear profiles where the strength and depth of the inversion are varied, as well as the amount of wind shear. MGWs are characterized in terms of response variables, such as wind speed perturbations (U'), temperature perturbations (T'), pressure perturbations (P'), potential temperature perturbations (Θ'), and the correlation coefficient (R) between U' and P'. Regime Diagrams portray the response of MGW to the above variables in order to better understand the formation, causes, and intensity of MGWs. The results of this study indicate that shallow, weak surface layers coupled with deep, neutral layers above favor the formation of waves of elevation. Conversely, deep strong surface layers coupled with deep, neutral layers above favor the formation of waves of depression. This is also the type of atmospheric setup that tends to produce substantial surface heating at the surface.

Analyse des données de la mission Gravity Recovery And Climate Experiment (GRACE) sur des bassins versants choisis au Canada pour la caractérisation des eaux souterraines.

Résumé : Les eaux souterraines ont un impact majeur sur la vie terrestre, les besoins domestiques et le climat. Elles sont aussi un maillon essentiel du cycle hydrologique. Au Canada par exemple, plus de 30 % de la population est tributaire des eaux souterraines pour leur alimentation en eau potable. Ces ressources subissent de nombreuses pressions sous l’influence de certains facteurs comme la salinisation, la contamination et l’épuisement. La variabilité du climat et la demande croissante sur ces ressources imposent l'amélioration de nos connaissances sur les eaux souterraines. L’objectif principal du projet de recherche est d’exploiter les données d’anomalies (TWS) de la mission Gravity Recovery And Climate Experiment (GRACE) pour localiser, quantifier et analyser les variations des eaux souterraines à travers les bassins versants du Bas-Mackenzie, du Saint-Laurent, du Nord-Québec et du Labrador. Il s’agit aussi d’analyser l’influence des cycles d’accumulation et de fonte de neige sur les variations du niveau des eaux souterraines. Pour estimer les variations des eaux souterraines, la connaissance des autres paramètres du bilan hydrologique est nécessaire. Ces paramètres sont estimés à l’aide des sorties du modèles de surface CLM du Système Global d’Assimilation des Données de la Terre (GLDAS). Les données GRACE qui ont été utilisées sont celles acquises durant la période allant de mars 2002 à août 2012. Les résultats ont été évalués à partir d’enregistrements de niveaux piézométriques provenant de 1841 puits localisés dans les aquifères libres du bassin des réseaux de suivi des eaux souterraines au Canada. Les valeurs de rendements spécifiques des différents types d’aquifères de chaque puits et celles des variations mensuelles du niveau d’eau dans ces puits ont été utilisées pour estimer les variations des anomalies des eaux souterraines in-situ. L’étude de corrélation entre les variations des anomalies des eaux souterraines estimées à partir de la combinaison GRACE-GLDAS et celles issues de données in-situ révèle des concordances significatives avec des valeurs de