Sedimentation, distribution and diagenesis of organic matter in a recent carbonate environment, Abu Dhabi, U.A.E.

In the modern hypersaline carbonate lagoon and sabkha sedimentary environments of Abu Dhabi (United Arab Emirates), three types of organic matter originate respectively from microbial mat, Avicennia mangrove, and Halodule lagoonal seagrass. The study of recent sedimentary processes and cross sections through the sabkha sediments lead to the definition of organo-sedimentary facies based on geochemical and sedimentological criteria. This permits the construction of an organo-sedimentary sequence which expresses the Holocene sedimentary record involving a transgressive and a regressive sequence. The various organic facies occur in both sequences.Heterogeneity within the individual organic facies reflects several factors, including sedimentation dynamics, mineral matrix, oxidation and reduction, and selective organic and mineral diagenesis. These parameters are discussed in terms of depositional environment and location within the organo-sedimentary sequence. Changes in distribution, quantity, and preservation potential of the buried organic matter are discussed in terms of sea level changes and sedimentary accretion rates.     

Morphology and Immune-related activities of hemocytes of the mussel Mytilus coruscus (Gould, 1861) from East Sea of Korea

Ocean Science Journal - Mytilus coruscus is a cold water mussel commonly occurring on shallow subtidal rocky substrata along the east coast of Korea. Despite its abundance, there have only been a...     

Cosmogenic radionuclides and mineralogical properties of the Chelyabinsk (LL5) meteorite: What do we learn about the meteoroid?

On February 15, 2013, after the observation of a brilliant fireball and a spectacular airburst over the southern Ural region (Russia), thousands of stones fell and were rapidly recovered, bringing some extremely fresh material for scientific investigations. We undertook a multidisciplinary study of a dozen stones of the Chelyabinsk meteorite, including petrographic and microprobe investigations to unravel intrinsic characteristics of this meteorite. We also study the short and long‐lived cosmogenic radionuclides to characterize the initial meteoroid size and exposure age. Petrographic observations, as well as the mineral compositions obtained by electron microprobe analyses, allow us to confirm the classification of the Chelyabinsk meteorite as an LL5 chondrite. The fragments studied, a few of which are impact melt rocks, contain abundant shock melt veins and melt pockets. It is likely that the catastrophic explosion and fragmentation of the Chelyabinsk meteoroid into thousands of stones was in part determined by the initial state of the meteoroid. The radionuclide results obtained show a wide range of concentrations of ¹⁴C, ²²Na, ²⁶Al, ⁵⁴Mn, ⁵⁷Co, ⁵⁸Co, and ⁶⁰Co, which indicate that the pre‐atmospheric object had a radius >5 m, consistent with other size estimates based on the magnitude of the airburst caused by the atmospheric entry and breakup of the Chelyabinsk meteoroid. Considering the observed ²⁶Al activities of the investigated samples, Monte Carlo simulations, and taking into account the ²⁶Al half‐life (0.717 Myr), the cosmic‐ray exposure age of the Chelyabinsk meteorite is estimated to be 1.2 ± 0.2 Myr. In contrast to the other radionuclides, ¹⁴C showed a very large range only consistent with most samples having been exposed to anthropogenic sources of ¹⁴C, which we associate with radioactive contamination of the Chelyabinsk region by past nuclear accidents and waste disposal, which has also been confirmed by elevated levels of anthropogenic ¹³⁷Cs and primordial ⁴⁰K in some of the Chelyabinsk fragments.     

Single crystal U-Pb zircon age and Sr-Nd isotopic composition of impactites from the Bosumtwi impact structure, Ghana: Comparison with country rocks and Ivory Coast tektites

The 1.07?Myr old Bosumtwi impact structure (Ghana), excavated in 2.1-2.2?Gyr old supracrustal rocks of the Birimian Supergroup, was drilled in 2004. Here, we present single crystal U-Pb zircon ages from a suevite and two meta-graywacke samples recovered from the central uplift (drill core LB-08A), which yield an upper Concordia intercept age of ca. 2145?±?82?Ma, in very good agreement with previous geochronological data for the West African Craton rocks in Ghana. Whole rock Rb-Sr and Sm-Nd isotope data of six suevites (five from inside the crater and one from outside the northern crater rim), three meta-graywacke, and two phyllite samples from core LB-08A are also presented, providing further insights into the timing of the metamorphism and a possibly related isotopic redistribution of the Bosumtwi crater rocks. Our Rb-Sr and Sm-Nd data show also that the suevites are mixtures of meta-greywacke and phyllite (and possibly a very low amount of granite). A comparison of our new isotopic data with literature data for the Ivory Coast tektites allows to better constrain the parent material of the Ivory Coast tektites (i.e., distal impactites), which is thought to consist of a mixture of metasedimentary rocks (and possibly granite), but with a higher proportion of phyllite (and shale) than the suevites (i.e., proximal impactites). When plotted in a Rb/Sr isochron diagram, the sample data points (n?=?29, including literature data) scatter along a regression line, whose slope corresponds to an age of 1846?±?160?Ma, with an initial Sr isotope ratio of 0.703?±?0.002. However, due to the extensive alteration of some of the investigated samples and the lithological diversity of the source material, this age, which is in close agreement with a possible "metamorphic age" of ～?1.8-1.9?Ga tentatively derived from our U-Pb dating of zircons, is difficult to consider as a reliable metamorphic age. It may perhaps reflect a common ancient source whose Rb-Sr isotope systematics has not basically been reset on the whole rock scale during the Bosumtwi impact event, or even reflect another unknown geologic event.     

Sequential assimilation of soil moisture and streamflow data in a conceptual rainfall–runoff model

Soil moisture is a key hydrological variable in flood forecasting: it largely influences the partition of rain between runoff and infiltration and thus controls the flow at the outlet of a catchment. The methodology developed in this paper aims at improving the commonly used hydrological tools in an operational forecasting context by introducing soil moisture data into streamflow modelling. A sequential assimilation procedure, based on an extended Kalman filter, is developed and coupled with a lumped conceptual rainfall–runoff model. It updates the internal states of the model (soil and routing reservoirs) by assimilating daily soil moisture and streamflow data in order to better fit these external observations. We present in this paper the results obtained on the Serein, a Seine sub-catchment (France), during a period of about 2 years and using Time Domain Reflectivity probe soil moisture measurements from 0–10 to 0–100 cm and stream gauged data. Streamflow prediction is improved by assimilation of both soil moisture and streamflow individually and by coupled assimilation. Assimilation of soil moisture data is particularly effective during flood events while assimilation of streamflow data is more effective for low flows. Combined assimilation is therefore more adequate on the entire forecasting period. Finally, we discuss the adequacy of this methodology coupled with Remote Sensing data.     

Financial market actors as urban policy-makers: the case of real estate investment trusts in Brazil

Focusing on the growth of Real Estate Investment Trusts in Brazil, the paper explores how financializing policy instruments intertwine financial markets and the urban built environment. It studies the career of REITs and questions the role of financial market capital and actors in urban dynamics. The paper uncovers three processes usually considered separately: i) how a network of public and private financial market actors coaxes state bodies into using their regulatory powers and financial resources to transform real estate into an asset class; ii) how the government-run financial market authority and banks lure urban households into liquid real estate through marketing and education campaigns; and iii) how asset managers are “applied economic geographers” insofar as they channel households’ capital into a selected cities and properties. The active role played by financial actors in the design, enhancement and implementation of such a policy instrument leads us to conclude on their role as urban policy-makers.     

Vertical accuracy evaluation of freely available latest high-resolution (30 m) global digital elevation models over Cameroon (Central Africa) with GPS/leveling ground control points.

Digital Elevation Models (DEMs) contain topographic relief data that are vital for many geoscience applications. This study relies on the vertical accuracy of publicly available latest high-resolution (30?m) global DEMs over Cameroon. These models are (1) the ALOS World 3D-30?m (AW3D30), (2) the Shuttle Radar Topography Mission 1 Arc-Second C-Band Global DEM (SRTM 1) and (3) the Advanced Spaceborne Thermal Emission and Reflection Global DEM Version 2 (ASTER GDEM 2). After matching their coordinate systems and datums, the horizontal positional accuracy evaluation was carried out and it shows that geolocation errors significantly influence the vertical accuracy of global DEMs. After this, the three models are compared among them, in order to access random and systematic effects in the elevation data each of them contains. Further, heights from 555 GPS/leveling points distributed all over Cameroon are compared to each DEM, for their vertical accuracy determination. Traditional and robust statistical measures, normality test, outlier detection and removal were used to describe the vertical quality of the DEMs. The test of the normality rejected the hypothesis of normal distribution for all tested global DEMs. Overall vertical accuracies obtained for the three models after georeferencing and gross error removal in terms of Root Mean Square (RMS) and Normalized Median Absolute Deviation (NMAD) are: AW3D30 (13.06?m and 7.75?m), SRTM 1 (13.25?m and 7.41?m) and ASTER GDEM 2 (18.87?m and 13.30?m). Other accuracy measures (MED, 68.3% quantile, 95% quantile) supply some evidence of the good quality of AW3D30 over Cameroon. Further, the effect of land cover and slope on DEM vertical accuracy was also analyzed. All models have proved to be worse in the areas dominated by forests and shrubs areas. SRTM 1 and AW3D30 are more resilient to the effects of the scattering objects respectively in forests and cultivated areas. The dependency of DEMs accuracy on the terrain roughness is evident. In all slope intervals, AW3D30 is performing better than SRTM 1 and ASTER GDEM 2 over Cameroon. AW3D30 is more representative of the external topography over Cameroon in comparison with two others datasets and SRTM 1 can be a serious alternative to AW3D30 for a range of DEM applications in Cameroon.     

The Phase A study of the ESA M4 mission candidate ARIEL

ARIEL, the Atmospheric Remote sensing Infrared Exoplanet Large survey, is one of the three M-class mission candidates competing for the M4 launch slot within the Cosmic Vision science programme of the European Space Agency (ESA). As such, ARIEL has been the subject of a Phase A study that involved European industry, research institutes and universities from ESA member states. This study is now completed and the M4 down-selection is expected to be concluded in November 2017. ARIEL is a concept for a dedicated mission to measure the chemical composition and structure of hundreds of exoplanet atmospheres using the technique of transit spectroscopy. ARIEL targets extend from gas giants (Jupiter or Neptune-like) to super-Earths in the very hot to warm zones of F to M-type host stars, opening up the way to large-scale, comparative planetology that would place our own Solar System in the context of other planetary systems in the Milky Way. A technical and programmatic review of the ARIEL mission was performed between February and May 2017, with the objective of assessing the readiness of the mission to progress to the Phase B1 study. No critical issues were identified and the mission was deemed technically feasible within the M4 programmatic boundary conditions. In this paper we give an overview of the final mission concept for ARIEL as of the end of the Phase A study, from scientific, technical and operational perspectives.