Deze samenvatting is niet beschikbaar in het Nederlands. Résumé L'analyse sédimentologique des couches de transition Eifelien-Givetien dans la région de Wellin montre le passage d'un sytème de rampe mixte siliciclastique et carbonatée à une plate-forme carbonatée de faible pente et sans barrière récifale vraie. L'évolution de la sédimentation est celle d'une mégaséquence d'accrétion littorale au cours de laquelle les corps sédimentaires s'empilent sous forme d'unités progradantes d'épaisseurs décamétriques. L'analyse du contenu de la macrofaune corallienne et de la microflore algaire révèle en premier lieu une très grande diversité et abondance des organismes. Plusieurs assemblages sont reconnus et leur extension verticale est précisée. Ces assemblages reflètent souvent les zonations de faciès au sein de la rampe et ne peuvent donc être utilisés à des fins stratigraphiques qu'avec prudence. La comparaison avec d'autre données du Synclinorium de Dinant montre que le domaine sédimentaire était déjà structuré en "blocs" ou panneaux au sommet de l'Eifelien, préfigurant la situation au Givetien inférieur où plusieurs blocs d'extension plurikilométrique sont connus. Dans ce contexte, la mise en évidence d'une nouvelle formation (dénommée provisoirement Formation X) entre les Formations de Jemelle et d'Hanonet, dans la partie supérieure de l'Eifélien, prend toute son importance: cette formation, épaisse d'environ 120 m et constituée de calcaires crinoïdiques et construits, souligne la présence d'un bloc dans la région de Wellin. Abstract The sedimentology of the Eifelian-Givetian boundary beds in the Wellin area indicates a transition frorn a siliciclastic-carbonate ramp to a gently sloping carbonate platform lacking a true reefal barrier. Prograding decametric sedimentary units form a littoral accretion megasequence. Corallian megafauna and algal microflora are highly diverse and abundant. Several communities are recognized in the ramp but they cannot be used for precise chronostratigraphic correlations. Comparison with other regions of the Dinant Synclinorium shows that the basin was already partitioned into blocks in Late Eifelian time. In Early Givetian several blocks of plurikilornetric extension are identified. In this context, recognition of a new formation, provisionnally called "Formation X", between the Jemelle and Hanonet Formations, is significant. This local unit, some 120 meters thick, is composed of crinoidal and reefal limestones and indicates the existence of a sharply subsiding block in the Wellin area.
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The performance of the dark spectrum fitting (DSF) atmospheric correction algorithm is evaluated using matchups between metre- and decametre-scale satellite imagery as processed with ACOLITE and measurements from autonomous PANTHYR hyperspectral radiometer systems deployed in the Adriatic and North Sea. Imagery from the operational land imager (OLI) on Landsat 8, the multispectral instrument (MSI) on Sentinel-2 A and B, and the PlanetScope CubeSat constellation was processed for both sites using a fixed atmospheric path reflectance in a small region of interest around the system&\#x2019;s deployment location, using a number of processing settings, including a new sky reflectance correction. The mean absolute relative differences (MARD) between in situ and satellite measured reflectances reach <20&\#x0025; in the Blue and 11&\#x0025; in the Green bands around 490 and 560 nm for the best performing configuration for MSI and OLI. Higher relative errors are found for the shortest Blue bands around 440 nm (30&\#x2013;100&\#x0025; MARD), and in the Red-Edge and near-infrared bands (35&\#x2013;100&\#x0025; MARD), largely influenced by the lower absolute data range in the observations. Root mean squared differences (RMSD) increase from 0.005 in the NIR to about 0.015&\#x2013;0.020 in the Blue band, consistent with increasing atmospheric path reflectance. Validation of the Red-Edge and NIR bands on Sentinel-2 is presented, as well as for the first time, the Panchromatic band (17&\#x2013;26&\#x0025; MARD) on Landsat 8, and the derived Orange contra-band (8&\#x2013;33&\#x0025; MARD for waters in the algorithm domain, and around 40&\#x2013;80&\#x0025; MARD overall). For Sentinel-2, excluding the SWIR bands from the DSF gave better performances, likely due to calibration issues of MSI at longer wavelengths. Excluding the SWIR on Landsat 8 gave good performance as well, indicating robustness of the DSF to the available band set. The DSF performance was found to be rather insensitive to (1) the wavelength spacing in the lookup tables used for the atmospheric correction, (2) the use of default or ancillary information on gas concentration and atmospheric pressure, and (3) the size of the ROI over which the path reflectance is estimated. The performance of the PlanetScope constellation is found to be similar to previously published results, with the standard DSF giving the best results in the visible bands in terms of MARD (24&\#x2013;40&\#x0025; overall, and 18&\#x2013;29&\#x0025; for the turbid site). The new sky reflectance correction gave mixed results, although it reduced the mean biases for certain configurations and improved results for the processing excluding the SWIR bands, giving lower RMSD and MARD especially at longer wavelengths (>600 nm). The results presented in this article should serve as guidelines for general use of ACOLITE and the DSF.
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RBINS Staff Publications 2020
