Deep-water sand-fairway mapping as a tool for tectonic restoration: decoding Miocene central Mediterranean palaeogeography using the Numidian turbidites of southern Italy

Abstract

As turbidity currents are sensitive to the geometry of the substrate across which they flow, the sedimentology of turbidites can chart the development of submarine structures and reveal regional palaeobathymetric connections. This rationale is applied to understand the tectonic evolution of the central Mediterranean in the early Miocene, using the African-sourced, hyper-mature Numidian sandstones and their immature, orogen-derived time-equivalents. In both Sicily and the southern Apennines, the Numidian sequence displays characteristics of confined-uncontained turbidites: grain-size breaks and coarse bedload indicative of ubiquitous flow bypass; short-range grain-size fractionation across flow; stacked sandy bed-sets in the flow axes. We reconstruct sand fairways for over 300 km across the region and propose that their causative flows, axially fed from north Africa, were confined along sinuous corridors created by active submarine thrusting. In contrast, orogen-derived turbidites (e.g. Reitano flysch, confined-contained turbidites) were ponded in mini-basins higher on the thrust wedge. The composite Apennine-Calabrian-Maghrebian orogen with its submarine thrust belt had occluded deep-water Tethyan connections through the central Mediterranean by early Miocene times. Palaeobathymetry across the submarine thrust belt increased northwards into the future Apennines. This study illustrates the utility of turbidite sedimentology, especially reconstructing sand fairways, in building palaeogeographical reconstructions of complex tectonic regimes.

Depositional Model for Turbidite Lobes in Complex Slope Settings Along Transform Margins: The Motta San Giovanni Formation (Miocene—Calabria, Italy)

“…Numerous paleogeographic reconstructions of this part of the Mediterranean region have been proposed (e.g. Boullin et al, 1986;Dercourt et al, 1986;Dewey et al, 1989;Faccenna et al, 2001;Critelli et al, 2011Critelli et al, , 2017Vitale and Ciarcia, 2013;Critelli, 2018;Butler et al, 2020;Romagny et al, 2020;Milia et al, 2021) and controversies that go far beyond the scope of our work still exist. No matter what the paleo-reconstruction was, during Langhian to Messinian (Middle to Late Miocene), the CPT was localized to the NW of present-day Sicily (Figure 1), conforming to a transform margin setting sensu Type 2a of Wilson (1965).…”

Editorial: Source or sink? Erosional and depositional signatures of tectonic activity in deep-sea sedimentary systems

“…Consequently, sediment routing may be divided into discrete cells with different sedimentary behaviour, due to a variety of processes, some affecting the land and the shelf, some the slope, and others the basin-plain (e.g., Gamberi, 2020). Amongst those occurring in the deep-sea, a major role is played by tectonics, which modify seafloor topography; this in turn dictates where and when sediments are generated, stored, and remobilised in the deep-sea (e.g., Butler et al, 2020;McArthur et al, 2022).…”