Stratigraphy of upper Quaternary shallow-water contourite drifts and paleoceanographic modeling of the Gulf of Taranto (Ionian Sea, Southern Italy)

Shallow-water contourite drifts are sediments deposited in the water depth range where bottom currents may reflect not only basin-scale thermohaline circulation but also local processes that can be controlled by sea-level changes and morpho-bathymetry. We investigate these processes in the Gulf of Taranto (Ionian Sea) by integrating high-resolution reflection seismics, morpho-bathymetry data, and gravity core data with Coastal Modeling System Wave and CMS-M2D numerical models. Both geophysical-geological data and numerical modeling coherently indicate that Latest Quaternary shallow-water contourite drifts formed in the NW sector of the gulf in response to the eustatic fall of the sea-level that induced a severe impact on the bottom current system. The sea level drop caused subaerial exposure of the summit of the Amendolara Ridge that formed an island off the eastern coasts of Calabria and also created a narrow passageway between the island themselves and the northern Calabria coastline. Stratigraphic data indicate that the contourite drifts are bounded at the bottom and at the top by two major unconformities, and show that the sediments drifts formed between the onset of the last interglacial and the Early Holocene (~ 11.500 years BP). The analysis of the stratal architecture allows for the recognition of various contourite facies assemblages, depending on the local sea floor morphology, bottom currents and water depth. These are mostly represented by: a) Drift complex, along incision to the NE of the Amendolara Bank; b) Sheeted drifts, along the northeastern slope of the Amendolara Bank; c) Elongate drift along the northern Calabria continental shelf and upper slope. Numerical models predict that during the LGM the wave induced currents flow is driven roughly parallel to the northern Calabria paleo-coastline and counterclockwise around the north-eastern flank of the Amendolara Bank. The wave-induced hydrodynamics reaches the maximum velocity of ~ 0.1 m/s. According to Shields diagram, the minimum value of the flow velocity which allows the sediments to be mobilized is approximately 0.8 m/s for the considered grain sizes. Therefore, the additional contribution of the wave-induced hydrodynamics at the basin-scale thermohaline circulation of low Adriatic and Ionian created favorable conditions for the occurrence of the contourite drifts. Local erosional features coupled with a substantial lack of contourite deposits is also observed, until the present-day, on the south-eastern flank of the Amendolara Bank, where the LIW flows from the central Ionian Sea towards the Gulf of Taranto.