Tectono-sedimentary processes shaping the West Sardinian margin and adjacent oceanic basin during the Plio-Quaternary (Western Mediterranean Sea)

Abstract

A seismic analysis of the Plio-Quaternary stratigraphy of the West Sardinian continental margin and adjacent oceanic basin was conducted using single- and multi-channel seismic profiles. Two main chronostratigraphic boundaries have been used: i) the Ms. horizon, marking the base of the Pliocene and corresponding to the top of the Messinian evaporites on the lower continental slope and deep basin, and the Messinian erosional truncation on the upper slope and shelf; and ii) the newly identified A0 horizon, marking the base of the Quaternary (2.6 Ma). This study reveals key geological features affecting the Pliocene and Quaternary deposits: a) salt tectonic structures, b) normal faults, c) volcanic structures, d) pockmarks, e) canyon systems, and f) regressive clinoform system. These features are linked to tectono-sedimentary processes such as vertical movements, magmatic activity, halokinesis and sediment dynamics. Vertical movements are associated with the thermal subsidence of the Oligo-Miocene basin opening, water and sediment loading/unloading during and after the Messinian Salinity Crisis, and Pleistocene uplift onshore. These movements resulted in the tilting of the margin, which influenced normal faulting through reactivation of Oligo-Miocene faults, and the Plio-Quaternary depositional patterns. Several normal faults acted as conduits for lower Pliocene magmatic activity and gas migration, forming volcanoes and pockmarks on the continental shelf and upper slope. Salt tectonics in the lower slope and deep basin produced diapirs and rollover structures, significantly impacting the thickness and distribution of Pliocene and, to a lesser extent, Quaternary deposits. Canyons system formation seems to be controlled by the interplay of the Quaternary sea-level fluctuations with the margin's ongoing tilting. Similarly, the regressive clinoform system also results from these two factors, but is further influenced by erosion of uplifted Sardinian onshore areas.