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Sedimentary dynamics on the southern insular shelf of Madeira Island : insights from geophysical and sediment sampling data
Publication . BELVISI, VIVIANA; Madeira, José Eduardo De Oliveira; Quartau, Rui Manuel do Amaral Branco de Oliveira; Romagnoli, Claudia
This work focuses on the sedimentary dynamics surrounding the southern shelf of Madeira Island (Atlantic Ocean) through the analysis of recent submarine clinoform bodies (SCBs) and bedforms using geophysical and sedimentological data. Geophysical data consist of multi-temporal bathymetries and seismic profiles. Bathymetries have been used to characterize the features from a morphological and morphometric point view. Seismic profiles have been used to investigate the architectures of SCBs. Sediment samples were used to characterize the sedimentary cover of the shelf and to understand sediment sources. The final aim of this work is to characterize the depositional and erosional features and to infer the processes behind their origin. Results allowed dividing the shelf in four sectors, which differ in terms of width and steepness, sedimentary cover, erosive and depositional features, and exposure to the energetic wave regime. The most exposed area is Sector 1. The shelf is very wide, has low gradients and the sedimentary cover is coarse. Sediments come mostly from cliff dismantling because stream discharge is low. SCBs are more extended, locally reaching the shelf edge and bedforms fields are oblique to the coastline. Sectors 2 and 3 are still influenced by the main wave regime but less. The shelf is narrower and steeper, and the sediment cover is fine. These areas are mainly influenced by stream discharge. SCBs are thicker but narrower in comparison to sector 1 and bedform fields are perpendicular to the coastline. Sector 4 is even narrower with higher gradients characterized by small and narrow SCBs and small perpendicular bedforms fields. The sediment is coarse but related to biogenic production except offshore the main streams where it is fine. The understanding of these shelf processes is relevant for the management of coastal risks, location of telecommunication cables and aquaculture infrastructures and the extraction of marine aggregates.
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Fundação para a Ciência e a Tecnologia
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OE
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SFRH/BD/146942/2019