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The area around the Tidra Island is a complex and highly dynamic clastic tidal flat system. The character of the northern part of this area is outlined, together with its sedimentary changes through time and the different depositional environments that shaped this coastal area in the last centuries are reconstructed. The multi-proxy approach together with 14 C-dating has led to the identification of four main types of deposits using the modern facies distribution as an analogue: (a) A ∼800–440 cal yr BP old sandy shoreface, (b) different types of tidal flats (sand to mudflat) that discontinuously developed on top of this older shoreface deposit, (c) seagrass stands in the most recent part of the sedimentary succession and (d) at least two storm deposits of various ages within the record. The interpretation of the cores’ highly non-continuous succession allows the postulation of a constructive sandy shoreface that covered large parts of the area. The in most cases erosive boundary between this older deposit and the overlying tidal flat deposits indicates that a short-lived event eroded parts of this sandy shoreface deposit. According to the latest studies, recent sea-level fluctuations can be excluded so it is suggested that a major storm event eroded parts of the sandy shoreface to about 2–2.5 m below the modern mean low water. This erosive storm event possibly produced accommodation space in the water column for the renewed accumulation of sediments so that tidal flat sediments could evolve on top of the sandy shoreface deposits. At least one other storm event led to further reshaping of the area and finally the modern tidal flats and seagrass stands in the proximity of Tidra Island formed. As shown in current research [e.g. Barusseau, J.P., Vernet, R., Saliege, J.F., Descamps, C., 2007. Late Holocene sedimentary forcing and human settlements in the Jerf el Oustani – Ras el Sass region (Banc d’Arguin, Mauritania). Geomorphologie-Relief Processus Environnement 1, 7–18], these observations are in contrast to the overall constructive coastline evolution the Golfe d’Arguin. This is probably linked to the exceptional position of the Tidra Island area that represents a morphological protrusion in the coastline and is thus also exposed to erosive processes rather than sediment accumulation. |
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