Submarine Depositional Terraces at Salina Island (Southern Tyrrhenian Sea) and Implications on the Late-Quaternary Evolution of the Insular Shelf

Abstract

Abstract:The integrated analysis of high-resolution multibeam bathymetry and single-channel seismic profiles around Salina Island allowed us to characterize the stratigraphic architecture of the insular shelf. The shelf is formed by a gently-sloping erosive surface carved on the volcanic bedrock, mostly covered by sediments organized in a suite of terraced bodies, i.e. submarine depositional terraces. Based on their position on the shelf, depth range of their edge and inner geometry, different orders of terraces can be distinguished. The shallowest terrace (near-shore terrace) is a sedimentary prograding wedge, whose formation can be associated to the downward transport of sediments from the surf zone and shoreface during stormy conditions. According to the range depth of the terrace edge (i.e., 10-25 m, compatible with the estimated present-day, local storm-wave base level in the central and western Mediterranean), the formation of this wedge can be attributed to the present-day highstand. By assuming a similar genesis for the deeper terraces, mid-shelf terraces having the edge at depths of 40-50 m and 70-80 m can be attributed to the late and early stages of the Post-LGM transgression, respectively. Finally, the deepest terrace (shelf-edge terrace) has the edge at depths of 130-160 m, being thus referable to the lowstand occurred at ca. 20 ka. Based on the variability of edge depth in the different sectors, we also show how lowstand terraces can be used to provide insights on the recent vertical movements that affected Salina edifice in the last 20 ka, highlighting more generally their possible use for neo-tectonic studies elsewhere. Moreover, being these terraces associated to different paleo-sea levels, they can be used to constrain the relative age of the different erosive stages affecting shallow-water sectors.

Late Quaternary paleo sea level geomorphological markers of opposite vertical movements at Salina volcanic island (Aeolian Arc)

“…Going further back in time, the SDTs recognized above the insular shelves of Salina are associated with relative sea level stillstands during the post‐LGM transgressive stage (Casalbore et al, , ), but they cannot easily be matched with specific points of the eustatic curve in the absence of reliable age constraints. However, some SDTs associated with the LGM in the south‐eastern submarine sector of Salina Island suggest a localized subsidence during the last 20 ka (Casalbore et al, ). This subsidence is more likely related to tectonic activity along NE–SW striking normal and transtensive faults forming graben‐like structures along the channel separating Salina from the nearby Lipari Island (Ventura et al, ), and it thus does not influence the generalized uplift suggested for Salina during the last deglaciation.…”

“…Going further back in time, the SDTs recognized above the insular shelves of Salina are associated with relative sea level stillstands during the post‐LGM transgressive stage (Casalbore et al, , ), but they cannot easily be matched with specific points of the eustatic curve in the absence of reliable age constraints. However, some SDTs associated with the LGM in the south‐eastern submarine sector of Salina Island suggest a localized subsidence during the last 20 ka (Casalbore et al, ).…”

“…At Salina, the SDTs are recognized at different depth ranges with depositional edges (i.e. offlap breaks) typically located between −10 and −160 m (Casalbore et al, ). The shallowest (near‐shore) SDT has a depositional edge at depths between −10 and −25 m that is compatible with the estimated modern, local storm‐wave base level, and is thus related to the present‐day seaward transportation of sand from the surf zone and shoreface during storms (Chiocci and Romagnoli, ; Quartau et al, ; Mitchell et al, ).…”

Neogene marine sediments and biota encapsulated between lava flows on Santa Maria Island (Azores, north‐east Atlantic): An interplay between sedimentary, erosional and volcanic processes

“…Such Pliocene–Pleistocene calcarenites in the Mediterranean area are common on storm‐dominated steep‐gradient margins (Massari & Chiocci, 2006). In the Aeolian archipelago, clinoform bodies have been reported around all islands, likely formed by downwelling offshore currents formed during storms (Chiocci & Romagnoli, 2004; Casalbore et al , 2018). All of these examples show similar deposits to the wedges of this study.…”

“…Also on Oahu, Tsutsui et al (1987) reported offshore transport of shelf sand during the passage of a hurricane. Similarly, the presence of thick sand bodies on the bank margins of the Little and Great Bahama Bank is explained by offshore transport of carbonate sands during storms (Hine et al, 1981;Chabaud et al, 2016). Lower Pleistocene calcarenitic clinoform bodies in Rhodes, Greece, are referred to storms in a regressive regime of a highstand system tract or a forced regression (Hanken et al, 1996;Hansen, 1999).…”