The northeastern coastal plain of Belgium was a well-developed region during the late medieval period when Bruges and a series of smaller harbours became connected to the North Sea via the Zwin tidal channel. Yet, ecological data related to the evolution of the regional environment of the former Zwin region are still lacking. Diatoms, pollen, and macrobotanical remains have been studied for the first time from two cores drilled in the surroundings of the lost harbour of Hoeke. The sediments in both cores were deposited in four successive tidal channel systems spanning the pre-Roman to late medieval periods. Marine tychoplanktonic and planktonic diatoms were dominant and confirmed the presence of open marine tidal channels, while marine epipsammic diatoms were specific to channel deposits (systems 1 and 4) and marine epipelic diatoms characterised channel and accretion deposits (systems 2 and 3). The sediments of the late medieval Zwin main channel and tributary (system 4) are both characterised by marine tychoplanktonic and epipsammic species. The palynomorphs were typical of marine tidal deposits and (reworked) peat, while macroremains pointed to freshwater plants growing in the vicinity. The palynomorphs (system 4) suggest a more open landscape associated with the extensive reclamation and embankment of the Zwin region. Diatoms in the superjacent tidal deposits indicate that the late medieval Zwin silted up rapidly. Keywords : Late Holocene, palynology, diatom analysis, tidal channel system, medieval harbour
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RBINS Staff Publications 2024
This study presents a first assessment of the Top-Of-Atmosphere (TOA) radiances measured in the visible and near-infrared (VNIR) wavelengths from PRISMA (PRecursore IperSpettrale della Missione Applicativa), the new hyperspectral satellite sensor of the Italian Space Agency in orbit since March 2019. In particular, the radiometrically calibrated PRISMA Level 1 TOA radiances were compared to the TOA radiances simulated with a radiative transfer code, starting from in situ measurements of water reflectance. In situ data were obtained from a set of fixed position autonomous radiometers covering a wide range of water types, encompassing coastal and inland waters. A total of nine match-ups between PRISMA and in situ measurements distributed from July 2019 to June 2020 were analysed. Recognising the role of Sentinel-2 for inland and coastal waters applications, the TOA radiances measured from concurrent Sentinel-2 observations were added to the comparison. The results overall demonstrated that PRISMA VNIR sensor is providing TOA radiances with the same magnitude and shape of those in situ simulated (spectral angle difference, SA, between 0.80 and 3.39; root mean square difference, RMSD, between 0.98 and 4.76 [mW m−2 sr−1 nm−1]), with slightly larger differences at shorter wavelengths. The PRISMA TOA radiances were also found very similar to Sentinel-2 data (RMSD 3.78 [mW m−2 sr−1 nm−1]), and encourage a synergic use of both sensors for aquatic applications. Further analyses with a higher number of match-ups between PRISMA, in situ and Sentinel-2 data are however recommended to fully characterize the on-orbit calibration of PRISMA for its exploitation in aquatic ecosystem mapping.
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