Morpho-stratigraphic evolution of a tectonically controlled canyon-channel system in the Gioia Basin (Southern Tyrrhenian Sea)

Abstract

The Gioia-Mesima Canyon-Channel System (GMS) incises the northern part of the Gioia Basin, a post-Tortonian intra-slope basin located along the south-eastern Tyrrhenian margin. Integration of multibeam, side scan sonar and seismic reflection data allowed to reconstruct the morpho-stratigraphic evolution of the GMS and the main factors controlling its development and maintenance. The GMS drains the entire continental margin and displays a complex morphology consisting in two main courses: the Gioia-Petrace Canyon and the Mesima Canyon-Channel. These courses run parallel to each other, changing from narrow straight to meandering geometry until they merge into a single, relatively straight lower reach, which debouches in the Stromboli Valley. Seismic reflection profiles and morphometric analysis highlight a strong tectonic control on GMS location and morphology throughout its course. At large scale, tectonic structures cross cutting the GMS caused both the formation of a mini-basin in the upper slope and a larger confined sub-basin downslope. These features promote abrupt changes in slope gradients that in turn are reflected on the plan-view morphology and stratigraphic architecture (seismic facies and sediment depocenters) of the GMS. Particularly, the progressive infilling of the confined sub-basin caused changes in the GMS base level, determining a polyphased evolution of the system encompassing repeated erosional and depositional events. The complete infill of the sub-basin promoted a by-pass of turbiditic flows in the lower slope, leading to the development of the lower reach of the GMS and its connection with the Stromboli Valley. This connection favoured a base level lowering of the GMS, causing its rejuvenation by retrogressive upslope erosion. This stage was recorded only in the shelf-indenting Gioia Canyon, characterized by a narrow and entrenched course, with irregular longitudinal profile and multiple knickpoints. Based on these results, we propose an evolutionary architectural model of the GMS to point out how erosional and depositional processes of channel/canyon system in a tectonically controlled margin can rapidly change in space and time in relation to multiple factors.