Influence of particle and surface quality on the vitrinite reflectance of dispersed organic matter: Comparative exercise using data from the qualifying system for reflectance analysis working group of ICCP

The development of a qualifying system for reflectance analysis has been the scope of a working group within the International Committee for Coal and Organic Petrology (ICCP) since 1999, when J. Koch presented a system to qualify vitrinite particles according to their size, proximity to bright components and homogeneity of the surface. After some years of work aimed at improving the classification system using photomicrographs, it was decided to run a round robin exercise on microscopy samples. The classification system tested consists of three qualifiers ranging from excellent to low quality vitrinites with an additional option for unsuitable vitrinites. This paper reports on the results obtained by 22 analysts who were asked to measure random reflectance readings on vitrinite particles assigning to each reading a qualifier. Four samples containing different organic matter types and a variety of vitrinite occurrences have been analysed. Results indicated that the reflectance of particles classified as excellent, good or poor compared to the total average reflectance did not show trends to be systematically lower or higher for the four samples analysed. The differences in reflectance between the qualifiers for any given sample were lower than the scatter of vitrinite reflectance among participants. Overall, satisfactory results were obtained in determining the reflectance of vitrinite in the four samples analysed. This was so for samples having abundant and easy to identify vitrinites (higher plant-derived organic matter) as well as for samples with scarce and difficult to identify particles (samples with dominant marine-derived organic matter). The highest discrepancies were found for the organic-rich oil shales where the selection of the vitrinite population to measure proved to be particularly difficult. Special instructions should be provided for the analysis of this sort of samples. The certainty of identification of the vitrinite associated with the vitrinite reflectance values reported has been assessed through a reliability index which takes into account the number of readings and the coefficient of variation. The same statistical approach as that followed in the ICCP vitrinite reflectance accreditation program for single seam coals has been used for data evaluation. The results indicated low to medium dispersion for 17 out of 22 participants. This, combined with data from other sets of comparative analyses over a long period, is considered an encouraging result for the establishment of an accreditation program on vitrinite reflectance measurements in dispersed organic matter.     

Diagnosis of Free and Convectively Coupled Equatorial Waves

A methodology for diagnosis of free and convectively coupled equatorial waves (CCEWs) is reviewed and illustrated for Kelvin and mixed Rossby–gravity (MRG) waves. The method is based on prefiltering of the geopotential and horizontal wind, using three-dimensional normal mode functions of the adiabatic linearized equations of a resting atmosphere, followed by space–time power and cross-spectral analysis applied to the normal-mode-filtered fields and the outgoing long-wave radiation (OLR) to identify spectral regions of coherence. The methodology is applied to geopotential and horizontal wind fields produced by European Centre for Medium-Range Weather Forecasts interim reanalysis and OLR data produced by the National Oceanic and Atmospheric Administration. The same type of data simulated by two climate models that participated in the fifth phase of the climate model intercomparison project are also used. Overall, simulation of free and CCEWs was achieved by the models with moderate success. Kelvin and MRG waves were identified in the space–time spectral domains, using both observationally based and climate model datasets. Other nonequatorial waves, classified as tropical depression and extratropical storm track activity, along with the Madden–Julian oscillation were also observed. However, significant deviations were also evident in the models, which may help identification of deficiencies in the models’ simulation schemes for some physical processes. Therefore, this diagnosis method should be a useful procedure for climate model validation and model benchmarking.     

New encoder–decoder convolutional LSTM neural network architectures for next-day global ionosphere maps forecast

GPS Solutions - In addition to traditional tide gauges, the ground-based global navigation satellite system reflectometry (GNSS-R) that utilizes signal-to-noise ratio data from a single GNSS...     

Advances in automated detection of sand dunes on Mars

This paper describes advances in an automatic approach for the detection of sand dunes of Mars, based on supervised learning techniques. A set of features (gradient histogram) is extracted from the remotely sensed images and two classifiers (Support Vector Machine and Random Forests) are trained from this data. The evaluation is conducted on 230 MOC‐NA images (spatial resolution between 1·45 and 6·80 m/pixel) leading to about 89% of correct detections. A detailed analysis of the detection results (dune/non‐dune) is performed by dune type or bulk shape, confirming high performances independently of the way the dataset is analysed. This demonstrates the robustness and adequacy of the automated approach to deal with the large variety of aeolian structures present on the surface of Mars. Copyright © 2012 John Wiley & Sons, Ltd.     

Carbon isotopes and geochemical processes in CO2-rich cold mineral water,N-Portugal

This paper summarizes a new outlook on the conceptual model of Melgaço–Messegães CO₂-rich cold (≈18 °C) mineral water systems, issuing in N of Portugal, based on their isotopic (²H, ³H, ¹³C, ¹⁴C and ¹⁸O) and geochemical features. Stable isotopes indicate the meteoric origin of these CO₂-rich mineral waters. Based on the isotopic fractionation with the altitude, a recharge altitude between 513 up to 740 m a.s.l. was estimated, corroborating the tritium results. The lowest ³H content (0 TU) is found in the groundwater samples with the highest mineralization. The mineral waters circulation are mainly related to a granitic and granodioritic environment inducing two different groundwater types (Ca/Na–HCO₃ and Na/Ca–HCO₃), indicating different underground flow paths. Calcium dissolution is controlled by hydrolysis of rock-matrix silicate minerals (e.g. Ca-plagioclases) and not associated to anthropogenic sources. The shallow dilute groundwaters exhibit signatures of anthropogenic origins (e.g. NO₃) and higher Na/Ca ratios. The stable isotopes together with the geochemistry provided no indication of mixing between the regional shallow cold dilute groundwater and mineral water systems. The heavy isotopic signatures identified in the δ¹³C data (δ¹³C = 4.7 ‰, performed on the total dissolved inorganic carbon (TDIC) of CO₂-rich mineral waters) could be derived from a deep-seated (upper mantle) source or associated to methanogenesis (CH₄ source). The negligible ¹⁴C content (≈2 pmC) determined in the TDIC of the mineral waters, corroborates the hypothesis of a mantle-derived carbon source to the mineral groundwater systems or dissolution of carbonate layers at depth.     

Significant variations in the productivity of green macroalgae in a mesotidal estuary: implications to the nutrient loading of the system and the adjacent coastal area

A spatially dynamic model for the productivity of spores and adults of green macroalgae (Enteromorpha sp.) was developed for a mesotidal estuary (Mondego estuary, Portugal). Many of the algal processes and parameters included in the model were experimentally obtained. Model predictions were compared to a real time series (1993-1997) of macroalgal biomass variation and the two sets show a good agreement (ANOVA, P<0.001). Results suggest that algal growth is highly sensitive to small changes in depth and exhibits different patterns of variation in different seasons. On a yearly basis, global calculations for the south channel of the estuary (137 ha) suggest that during bloom years, macroalgal biomass may reach about 21,205 ton DW compared to 240 ton DW in regular years. On a seasonal basis, the difference may be even more significant. The consequences of such variations on the nitrogen and phosphorus loading of the system and the adjacent coastal area are discussed.     

Vertical deformation partitioning across a collapsing large and hot orogen

Featuring 3 000-km-long large and hot orogen, the Mantiqueira Province provides a rare opportunity to study the process of gravitational collapse at mid to deep crustal levels. Distinct but contemporary (~500 Ma) post-collisional intrusions show structures and anisotropy of magnetic susceptibility (AMS) fabrics related to their emplacements, recording different flow patterns. In southern deep-seated intrusions, ellipsoidal-shaped roots with gabbroic-to-hybrid cores surrounded by granitic rocks show concentric patterns of AMS fabrics that cut across the NE-trending regional foliation. In contrast, northern intrusions, exposed as the upper sections of batholith-size bodies of coarse-grained granite emplaced at the shallow to mid-crust, show general NS-trending magnetic fabrics roughly parallel to strike of the orogen and the regional foliation of host rocks. These contrasting magnetic patterns from shallow to deeper crust suggest vertical magma migration from the overthickened orogenic core to be emplaced across its thinner stretched flanks during the gravitational collapse of the orogenic edifice.