Multi‐scale analysis of a migrating submarine channel system in a tectonically‐confined basin: The Miocene Gorgoglione Flysch Formation, southern Italy

Abstract

The Miocene Gorgoglione Flysch Formation records the stratigraphic product of protracted sediment transfer and deposition through a long‐lived submarine channel system developed in a narrow and elongate thrust‐top basin of the Southern Apennines (Italy). Channel‐fill deposits are exposed in an outcrop belt approximately 500 m thick and 15 km long, oriented oblique to the palaeoflow, which was roughly south‐eastward. These exceptional exposures of channel‐fill strata allow the stacking architectures and the evolution of the channel system to be analyzed at multiple scales, enabling the effects of syn‐sedimentary thrust tectonics and basin confinement on the depositional system development to be deciphered. Two end‐member types of elementary channel architecture have been identified: high‐aspect‐ratio, weakly‐confined channels, and low‐aspect‐ratio, incisional channels. Their systematic stacking results in a complex pattern of seismic‐scale depositional architectures that determines the stratigraphic framework of the deep‐water system. From the base of the succession, two prominent channel complex sets have been recognized, namely CS1 and CS2, consisting of amalgamated incisional channel elements and weakly‐confined channel elements. These channelized units are overlain by isolated incisional channels, erosional into mud‐prone slope deposits. The juxtaposition of different channel architectures is interpreted to have been governed by regional thrust‐tectonics, in combination with a high subsidence rate that promoted significant aggradation. In this scenario, the alternating ‘in sequence’ and ‘out of sequence’ tectonic pulses of the basin‐bounding thrusts controlled the activation of coarse‐clastic inputs in the basin and the resulting stacking architectures of channelized units. The tectonically‐driven confinement of the depositional system limited the lateral offset in channel stacking, preventing large‐scale avulsions. This study represents an excellent opportunity to analyze the stratigraphic evolution of a submarine channel system in tectonically‐active settings from an outcrop perspective. It should find wide applicability in analogous depositional systems, whose stratigraphic architecture has been influenced by tectonically‐controlled lateral confinement and associated lateral tilting.

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

“…Our work is consistent with other studies indicating that structurally confined but uncontained turbidite systems leave sand-rich fairways comprising stacked bed-sets (e.g. Liu et al 2018;Casciano et al 2019). These turbidite sand fairways reflect not only the connectivity between arrays of basins but also the relative elevation of parts of the basin floor.…”

The evolution of submarine slope-channel systems: Timing of incision, bypass, and aggradation in Late Cretaceous Nanaimo Group channel-system strata, British Columbia, Canada

“…Submarine channels have multiphase evolutionary histories that include periods of erosion, sediment bypass, and deposition (e.g., Deptuck et al, 2003Deptuck et al, , 2007McHargue et al, 2011;Fildani et al, 2013;Hubbard et al, 2014;Hodgson et al, 2016;Covault et al, 2016;Casciano et al, 2018). These processes are recorded in deepwater deposits and result in stratigraphic products that are characterized by diachronous erosional surfaces and heterogeneous fill ( Fig.…”

Syndepositional tectonics and mass-transport deposits control channelized, bathymetrically complex deep-water systems (Aínsa depocenter, Spain)

“…A flow may be partially or fully confined by prominent basin-floor topography, or by a channel wall composed of incised substrate or overspill deposits. These overspill deposits (commonly referred to as terraces or internal levees; Hansen et al, 2015) may themselves be confined within larger external levees (Kane and Hodgson, 2011), a canyon wall (Kane et al, 2009a), or by confining structures (Casciano et al, 2019). At flow scale, substrate erosion (Eggenhuisen et al, 2011), construction of depositional topography (e.g., levees) from preceding flows (De Leeuw et al, 2016), or both (Hodgson et al, 2016), can progressively generate lateral confinement, increasing the velocity, and hence bypass potential of subsequent flows (Fig.…”

“…To help bridge the resolution gap between event-bed and seismic scale, outcrops from ancient structurally complex basins are commonly used as analogs (e.g., McCaffrey et al, 2002;Brunt et al, 2007;Leren et al, 2007;Janbu et al, 2007;Hubbard et al, 2008;Bernhardt et al, 2011Bernhardt et al, , 2012Casciano et al, 2019;McArthur and McCaffrey, 2019). One such "natural laboratory" is the Eocene Hecho Group, in the Aínsa depocenter (South Pyrenean Foreland Basin, Spain), where the effect of structures and mass-transport deposits on deepwater channels has been well documented (Pickering and Corregidor, 2005;Arbués et al, 2007aArbués et al, , 2007bPickering and Bayliss, 2009;Dakin et al, 2013;Bayliss and Pickering, 2015).…”