Search publications of the members of the Royal Belgian institute of natural Sciences
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Time-series analysis of SAR images for detecting ground subsidence in the Scheldt estuary
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Overview of the ground mouvements highlighted by the Persistent Scatterer Technique (PSI) in Belgium
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Genesis of the vein-type tungsten mineralization at Nyakabingo (Rwanda) in the Karagwe–Ankole belt, Central Africa
- The vein-type tungsten deposit at Nyakabingo in the central Tungsten belt of Rwanda is located in the eastern flank of the complex Bumbogo anticlinal structure. The host rock is composed of alternating sequences of sandstones, quartzites, and black pyritiferous metapelitic rocks. Two types of W-mineralized quartz veins have been observed: bedding-parallel and quartz veins that are at high angle to the bedding, which are termed crosscutting veins. Both vein types have been interpreted to have been formed in a late stage of a compressional deformation event. Both vein types are associated with small alteration zones, comprising silicification, tourmalinization, and muscovitization. Dating of muscovite crystals at the border of the veins resulted in a maximum age of 992.4 ± 1.5 Ma. This age is within error similar to the ages obtained for the specialized G4 granites (i.e., 986 ± 10 Ma). The W-bearing minerals formed during two different phases. The first phase is characterized by scheelite and massive wolframite, while the second phase is formed by ferberite pseudomorphs after scheelite. These minerals occur late in the evolution of the massive quartz veins, sometimes even in fractures that crosscut the veins. The ore minerals precipitated from a H2O–CO2–CH4–N2–NaCl–(KCl) fluid with low to moderate salinity (0.6–13.8 eq. wt% NaCl), and minimal trapping temperatures between 247 and 344 °C. The quartz veins have been crosscut by sulfide-rich veins. Based on the similar setting, mineralogy, stable isotope, and fluid composition, it is considered that both types of W-mineralized quartz veins formed during the same mineralizing event. Given the overlap in age between the G4 granites and the mineralized quartz veins, and the typical association of the W deposits in Rwanda, but also worldwide, with granite intrusions, W originated from the geochemically specialized G4 granites. Intense water–rock interaction and mixing with metamorphic fluids largely overprinted the original magmatic-hydrothermal signature.
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The map of the Brabant Massif for offshore Belgium
- The cartographic boundary of the Brabant Massif in the northwest is the North Sea, which is an observational limit. Nevertheless the Lower Palaeozoic rocks continue as part of a larger unit, referred to as the Anglo-Brabant Deformation Belt. Maps of the Brabant Massif largely rely on borehole data. The latest map of the Brabant Massif (Piessens et al., 2005) uses structural concepts and direct information, rather than geophysical information. Nevertheless, an aeromagnetic survey and gravimetric data corroborate the large scale distribution of the units. This map is extrapolated to the off-shore territory of Belgium. Direct information from drillings is not available for the off-shore region, and it is therefore not possible to draw this map at the same stratigraphic resolution. The formations are therefore grouped into Cambrian, Ordovician and Silurian units. Magnetic susceptibility is high for the Cambrian, which allows tracing their continuation from on-shore to off-shore. The formations at subcrop level along the central axis of the Brabant Massif are on-shore Cambrian in age, but young in a WNW direction. Also the magnetic pattern becomes less intense, likely corresponding to an increasing depth of the more magnetic lower Cambrian units. This trend continues off-shore, indicating that the Cambrian units disappears at subcrop level. Superimposed on this general trend an aeromagnetic anomaly about 15 km off-shore of Ostend marks the probable local reappearance of the Tubize Formation. A secondary and less continuous Cambrian axis passes near Diksmuide. A second isolated off-shore aeromagnetic anomaly, indicative of the Cambrian unit, lies along the trace of this secondary axis. The gravimetric map shows a low gravimetric anomaly of which the circular shape suggests a genetic link with the chain of gravimetric lows that underlie the southern part of the on-shore part of the Brabant Massif. The higher densities in the northern part of the off-shore territory confirm, in continuation of the on-shore formation boundaries, the presence of the Silurian unit. The validity of the inferred distribution of the stratigraphic units was verified with the structural 3D concept that was developed for the on-shore part of the Brabant Massif, concluding that the inferred distribution of the geological units is in agreement with the structural model derived on-shore. It for example explains the positions of the two magnetic anomalies relative to each another. A central element in the structural model is the Asquempont Detachment System of which a limited number of possible traces is possible.
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Beyond the current limits of Raman Spectroscopy: controlling fluorescence in solid bitumen with low thermal maturity
- Raman spectroscopy is an interesting tool to assess the thermal maturity of solid organic matter. For carbonaceous material with moderate to high maturities, several studies have found good correlations between Raman spectral parameters and thermal maturity, expressed as vitrinite reflectance (VR) or bitumen reflectance (BR). However, at low maturities a large part of the Raman peaks is lost under an intense background radiation, caused by fluorescence. This fluorescence problem mainly occurs at 0.4-1.0% VR (the oil window), and makes it difficult to recognize the original spectrum. In this study, Raman parameters that have been put forward in literature were tested on a low maturity, solid bitumen sample of approximately 0.61% BR. The investigated parameters include the peak’s full width at half maximum FWHM, peak position W, peak area A, area ratio AD/AG and intensity ratio ID/IG. Fluorescence in this sample is very high and covers Raman peaks. It was found that during consecutive measurements at a single location (i.e. irradiation with the Raman laser), fluorescence decreases with time and Raman peaks appear. This is in line with Quirico et al. (2005), who observed the same effect at coal measurements. An interesting observation is the behaviour of Raman parameters during ongoing irradiation. The full widths at half maximum do not change at all for every investigated peak in our spectra. Also peak positions remain the same. The peak areas do change with irradiation, and show a decrease with decreasing fluorescence. Comparison of areas under individual peaks and total spectrum area however suggests that A and fluorescence decrease at equal speeds. This is the case for most important Raman peaks at 1370 (D-band), 1600 (G-band) and 3200 cm-1, with correlation coefficients of 0.66, 0.97 and 0.92 respectively. Lastly, the area ratio AD/AG and intensity ratio ID/IG(approximation) show no trend with fluorescence, indicating that the shape of the spectrum remains the same with irradiation. This is a promising result, because it suggests that fluorescence can be controlled without changing spectral parameters. Although not all peak parameters in this study (FWHM and AD/AG) correspond to parameters from literature regarding maturity, the behaviour of the Raman peak parameters in combination with the decreasing fluorescence is an exciting outcome. If further research proves that the original parameters are not altered by irradiation, this will provide an answer to the problem of fluorescence at low maturity samples.
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Example of natural fracture patterns in Westphalian deposits: occurence and controls
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Het archeozoölogisch en carpologisch onderzoek van een afvalpakket op de site Eenmansstraat in de Brusselse beenhouwerswijk (BHG)
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Zaden en vruchten uit middeleeuws en post-middeleeuws Brussel (BHG)
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Rapport des activités et des résultats réalisés en 2015
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What if jellyfish were swimming?
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Are juveniles from mixed spawning populations or not? Tracing juvenile sole arriving at the Belgian nursery using genomics and otolith shape
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River-Ocean Models as Support to eutrophication management
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Short-term effects of fishery exclusion in offshore wind farms on macrofaunal communities in the Belgian part of the North Sea
- With the wide scale construction of offshore wind farms (OWFs) throughout the entire North Sea, largeareas are permanently being closed to beam trawl fisheries. Beam trawling has affected macrobenthicassemblages for centuries, especially the fragile and long-lived species. Due to the prohibition of beantrawling in many OWFs, opportunities are being provided to investigate the potential recovery of vulnera-ble species and the creation of de-facto Marine Protected Areas (MPAs). The soft-substrate macrobenthiccommunity was investigated from 2008 to 2012, before and after the construction of an OWF in theBelgian part of the North Sea, situated on the Bligh Bank. The fishery enclosed area (±21 km2) withinthe OWF (No Fishery area) was compared with a surrounding control area (±30 km2) where regularfishing activities were registered through vessel monitoring system (VMS) data throughout the period2010–2011. Three years after the exclusion of beam trawl fisheries, subtle changes within the macroben-thic community were observed in the No Fishery area. The benthic mysid shrimp Gastrosaccus spinifer(30 ± 15 ind m−2), tube-building polychaetes Terebellidae sp. (196 ± 151 ind m−2) and the echinodermEchinocyamus pusillus (73 ± 71 ind m−2), sensitive to trawling activities, showed increased abundanceswithin the No Fishery area. With an expansion of the wind farm concession area to 238 km2in the future,the likely increase of dense Terebellidae patches (e.g., Lanice conchilega reefs) within the No Fishery areacould create an ecological important large-scale refugium for higher trophic levels. This study creates abaseline for the evaluation of long-term changes due to the fishing impacts and effects related to the pres-ence of OWFs and highlights the importance of executing long-term monitoring programs in combinationwith targeted research.
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Neandertal cannibalism and Neandertal bones used as tools in Northern Europe
- Almost 150 years after the first identification of Neandertal skeletal material, the cognitive and symbolic abilities of these populations remain a subject of intense debate. We present 99 new Neandertal remains from the Troisième caverne of Goyet (Belgium) dated to 40,500–45,500 calBP. The remains were identified through a multidisciplinary study that combines morphometrics, taphonomy, stable isotopes, radiocarbon dating and genetic analyses. The Goyet Neandertal bones show distinctive anthropogenic modifications, which provides clear evidence for butchery activities as well as four bones having been used for retouching stone tools. In addition to being the first site to have yielded multiple Neandertal bones used as retouchers, Goyet not only provides the first unambiguous evidence of Neandertal cannibalism in Northern Europe, but also highlights considerable diversity in mortuary behaviour among the region’s late Neandertal population in the period immediately preceding their disappearance.
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Unequal contribution of native South African phylogeographic lineages to the invasion of the African clawed frog, Xenopus laevis, in Europe
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Pleistocene Mitochondrial Genomes Suggest a Single Major Dispersal of Non-Africans and a Late Glacial Population Turnover in Europe
- How modern humans dispersed into Eurasia and Australasia, including the number of separate expansions and their timings, is highly debated [ 1, 2 ]. Two categories of models are proposed for the dispersal of non-Africans: (1) single dispersal, i.e., a single major diffusion of modern humans across Eurasia and Australasia [ 3–5 ]; and (2) multiple dispersal, i.e., additional earlier population expansions that may have contributed to the genetic diversity of some present-day humans outside of Africa [ 6–9 ]. Many variants of these models focus largely on Asia and Australasia, neglecting human dispersal into Europe, thus explaining only a subset of the entire colonization process outside of Africa [ 3–5, 8, 9 ]. The genetic diversity of the first modern humans who spread into Europe during the Late Pleistocene and the impact of subsequent climatic events on their demography are largely unknown. Here we analyze 55 complete human mitochondrial genomes (mtDNAs) of hunter-gatherers spanning ∼35,000 years of European prehistory. We unexpectedly find mtDNA lineage M in individuals prior to the Last Glacial Maximum (LGM). This lineage is absent in contemporary Europeans, although it is found at high frequency in modern Asians, Australasians, and Native Americans. Dating the most recent common ancestor of each of the modern non-African mtDNA clades reveals their single, late, and rapid dispersal less than 55,000 years ago. Demographic modeling not only indicates an LGM genetic bottleneck, but also provides surprising evidence of a major population turnover in Europe around 14,500 years ago during the Late Glacial, a period of climatic instability at the end of the Pleistocene.
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Practical key to identify entire edible insects sold as foodstuff or feedstuff in central Europe
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Delafossite structure of heterogenite polytypes (HCoO2) by Raman and infrared micro-spectroscopy
- Heterogenite is commonly referred in mineralogy literature as a cobalt oxy-hydroxide CoO(OH). However, detailed analysis of Raman and infrared spectra acquired on particularly well-crystallized natural samples of heterogenite suggests that the mineral can be characterized by a delafossite-type structure, with a general chemical formula ABO2. Indeed, the Raman spectrum of heterogenite, along the one with grimaldiite (HCrO2), lacks visible free OH-group vibrational modes, while the infrared spectrum shows strong hydrogen bond absorption bands. HCoO2 is thus a better formulation of heterogenite that describes more clearly its vibrational behavior and avoids the confusion in literature. Electronic backscattered diffraction (EBSD) is then used to distinguish and map the 2H and 3R heterogenite natural polytypes for the first time. The comparison of EBSD and Raman mappings clearly indicates that the 2H polytype is characterized by an additional peak at 1220 cm− 1. It's presence/absence is therefore an efficient tool to distinguish both polytypes.
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Manganese layered oxides (asbolane, lithipophorite and intermediates) identification and characterization by Raman and infrared spectroscopy
- In this study, Raman and infrared spectroscopy is applied to investigate two manganese oxide phases: lithiophorite [(Al,Li)Mn4+O2(OH)2] and asbolane [(Ni,Co)xMn4+(O,OH)4.nH2O], along with their intermediates (“Asbolane-Lithiophorite Intermediates”: ALI). These oxides typically incorporate variable concentrations of Co, Ni, Cu and Li. They represent a group of economically interesting phases that are difficult to identify and characterize with classical X-ray diffraction techniques. They were described in many places around the world, including the oxidized horizon of large ore deposits in New-Caledonia, Australia, the Democratic Republic of the Congo (DRC) amongst others. They also represents phases encountered as Ni-Co enriched manganese nodules of the deep ocean floors. Our results show that Lithium-bearing manganese oxides with typical X-ray diffraction lines of lithiophorite can exhibit two different Raman responses, namely the one of a typical lithiophorite and the one of ALI. This difference of reaction between X-ray and Raman methods strengthen the model developed in literature [2] that the X-ray diffraction lines of these oxides result primarily from one component of the structure, the MnO6 octahedra layers. In the same way, the reflectors associated with the unstructured Ni-Co oxide layers in asbolane are too weak to be visible on X-ray diffraction patterns. By contrast, the Raman responses are also driven by the chemical composition of the samples, allowing a more precise characterization. We propose reference Raman spectroscopic signatures for lithiophorite, asbolane and ALI phases. These spectra are mainly composed of two spectral domains, the first one is located between 370-630 cm-1 and the second one between 900-1300 cm-1. We then assess the impact of their highly variable chemistry on their Raman peak positions, intensities and FWHM using a semi-systematic curve-fitting method profiled for these phases. The strong affinities observed between the Raman spectral content of asbolane, lithiophorite and their intermediates, combined with the progressive trend observed for some peak parameters indicate that the studied phases represent probably a solid solution.
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Aerial imagery from an high-altitude drifting balloon platform : applications in geohazards monitoring (Sierra Arana, Spain and Mons Province, Belgium)
- A new type of untethered balloon based mapping platform allows affordable remote sensing applications from higher altitudes and with a greater range and payload capacity than common motorized UAV’s. The airborne device, called « Stratochip » is based on a dual helium balloons configuration. At a defined altitude (comprised between 500 and 30000m), the first balloon is released, drastically reducing the platform climbing rate. The payload (up to 10kg) can then drift in a sub-horizontal trajectory until it leaves a pre-defined area of interest. Leaving the pre-defined area, the second balloon is released and the payload is recovered after a parachute landing. The predicted flight path of the Stratochip, launch site and surveyed area are calculated using both forecasted (NOAA model) and real-time (inborne instruments) meteorological data, along with the physical parameters of the balloons and parachute. The predicted recovery area can also be refined in real-time to secure and facilitate equipment retrieval. In this study, we present the results of two cartographic campaigns made in Belgium (Ground collapse near Mons) and Spain (karstic field in the Eastern part of Sierra Arana, Granada region). Those campaigns aimed to test the usability of the Stratochip to survey a large area (up to 900km² for Spain) at medium and low altitudes (8000m - 500m) and produce an updated Digital Elevation Model and orthophoto mosaic of those regions. For that purpose, the instrument installed in the Stratochip payload was constituted of a digital camera stabilized with two IMU’s and two brushless motors. An automated routine then tilted the camera at predefined angles while taking pictures of the ground. This technique allowed to maximize the photogrammetric information collected on a single pass flight, and improved the DEM reconstruction quality, using structure-from-motion algorithms. The quality of produced DEM were then evaluated by comparing the level and accuracy of details and surface artefacts between available topographic data (LIDAR, SRTM, topographic maps) and the Stratochip sets. This evaluation showed that the models were in good correlation with existing data, and can be readily be used in geomorphology, structural and natural hazard studies.
