Compatibility between Continental Shelf Deposits and Sediments of Adjacent Beaches along Western Sardinia (Mediterranean Sea)

Abstract

The compatibility of sediments in terms of grain size, composition and colour among beaches and strategic sediment deposits (SSD) along Western Sardinia (Western Mediterranean Sea) were assessed to explore management strategy in the protection and adaptation to counteract the beach erosion and the effect of sea level rise along sandy shores. Twelve beaches, mainly conditioned by geological control, due to the presence of extensive rocky outcrops in the sea, enclosed in seven sedimentary cells (defined by the continuity of sediment transport pathways and by identification of boundaries where there are discontinuities), were characterised in terms of sediment composition and grain size. One hundred ninety-three beach sediments and one hundred sediments from SSDs were collected and analysed for sediment grain size, carbonate content and sediment colour. The beach sediments are composed by gravel to fine sands (D50: from 81 µm to 4986 µm) with siliciclastic and biogenic carbonate sediments mixed in different proportions (0–100% in CaCO3). The SSDs sediments are gravels to medium-fine sand (D50: from 96 µm to 1769 µm) composed by biogenic carbonate sands mixed with siliciclastic grains (0–100% in CaCO3). To be able to evaluate the compatibility between the beaches and SSDs, a multivariate statistical procedure was applied to grain size dataset. Our results show that 8 beaches have strategic deposits of compatible grain size and composition, whereas only 2 beaches have compatible strategic deposits of both grain size and colour. This may be related to the different sediment sources and depositional processes of sediment along the coastal cells and the continental shelf.