Present morphology and depositional architecture of a sandy confined submarine system: the Golo turbidite system (eastern margin of Corsica)

Abstract

Abstraet:The modern sandy Golo turbidite system (500 km 2) is located in a confined basin on the eastern margin of Corsica. The Golo turbidite system is fed by a single river, which supplies coarse sand derived from active weathering of the neighbouring mountains. The late Quaternary deposits have been imaged using a closely spaced grid of 1000 km of sparker seismic-reflection profiles (line spacing close to 1.6 km, vertical resolution of 2 m). The turbidite system is composed of four non-coalescent fans that were at times active simultaneously and of two small deposits onto the slope. The resulting sedimentation pattern is characterized by stacked turbidite deposits. At a regional scale, there is a continuum of fan morphologies and geometries from south to north. The use of both seismic and sedimentary facies, together with mapped seismic geometry of sedimentary bodies, allowed definition of four architectural elements: (1) submarine valley (canyon and gully), (2) sandy channel, (3) muddy levee, and (4) sandy lobe. Some of these architectural elements can be recognized at a scale that is comparable to outcrop examples. Features such as progressive lateral migration and avulsion, or complex longitudinal evolution (progradation and retrogradation), can also be accurately described. Despite the active tectonics along the studied margin, the main variations in sedimentation appear to be controlled by eustatic changes, pre-existing seafloor topography, and sediment source characteristics. The general pattern of sedimentation is controlled by the influence of a confining slope, leading to the predominance of aggradation and to specific morphology and architecture of sedimentary bodies.

Two fundamentally different types of submarine canyons along the continental margin of Equatorial Guinea

“…Commonly, Type I canyons are associated with high sediment supply, either a fluvial system or longshore drift cell that supplies sand and gravel to the shallow canyon heads (Fig. 12;Inman et al 1976;O'Connell et al, 1987;Weaver et al, 2000;Covault et al 2007;Green and Uken, 2008;Yu et al, 2009 Gervais et al, 2004;Bertoni and Cartwright, 2005;Cunningham et al, 2005;Arzola et al, 2008;Lastras et al, 2009). The morphology and evolution of Type I canyons is controlled by sand-rich, erosive turbidity currents and mass wasting processes (Table 1; Ericson et al, 1952;Field and Gardner, 1990;Pratson et al, 1994;Pratson and Coakley, 1996;Weaver et al, 2000;Bertoni and Cartwright, 2005;Yu et al, 2009).…”

“…1; Shepard and Emery, 1973;Shepard, 1981;Gervais et al, 2004;Bertoni and Cartwright, 2005;Cunningham et al, 2005;Antobreh and Krastel, 2006;Lastras et al, 2009;Mountjoy et al, 2009;Armitage, et al, 2010). Many are associated with areas of high sediment supply (Weaver et al, 2000), such as coastal mountain belts (Gervais et al, 2004), large fluvial systems (Burke, 1972;Shepard and Emery, 1973;Shepard, 1981;McGregor et al, 1982;McHargue and Webb, 1986;O'Connell et al, 1987;Green and Uken, 2008;Yu et al, 2009) or vigorous longshore drift cells (Moore, 1969;Burke, 1972;Inman et al, 1976;Paull et al, 2005;Covault et al, 2007). These high sediment supply areas commonly have sharply defined shelf edges, steep upper slopes, and numerous shelf-indenting canyons (Fig.…”

Erosional sculpting of the Caprera confined deep-sea fan as a result of distal basin-spilling processes (eastern Sardinian margin, Tyrrhenian Sea)

“…sediments to the heads of the tributary canyons of the CDF could thus come from longshore currents flowing from the northern Corsica shelf (Millot, 1987;Artale et al, 1994;Millot, 1999). A similar disconnection of canyons from river-fed sediment supply during high stand periods of sea level has been proved for the fans of the nearby Corsica margin (Gervais et al, 2004). In the same area however, rivers supply sediment to the canyon heads during low sea level periods (Gervais et al, 2004).We thus assume that a comparable feeding system is active during low stand of sea levels in the CDF.…”

“…However, a detailed stratigraphic framework has been established for the recent depositional history of the nearby fans of the Corsica margin (Gervais et al 2004). The Corsica margin has a physiographic setting and a nature of the feeding hinterland similar to the study area that thus presumably share analogue variations in sediment supply mechanisms during the different sea level stands.…”

“…Thus in the upper part of the CDF it runs along the channel axis and does not show the associated levee wedge. smaller lobes develop during rising sea level trajectories and result in a backstepping of the systems (Gervais et al, 2004). Finally, hemipelagic deposition is prevailing during the present-day high stand conditions (Gervais et al, 2004).…”