Delta-Fed Turbidites Infilling Topographically Complex Basins: A New Depositional Model for the Annot Sandstones, SE France

Abstract

The Eocene-Oligocene Annot Sandstones of southeast France record the predominantly deep-water, siliciclastic infill of the early French Alpine foreland basin. They accumulated in a topographically complex basin as recorded by variable onlap relationships with the underlying Globigerina Marls. Onlap configurations and paleobathymetric data from the western outcrops of the Annot Sandstones enables a contour map of the pre-Annot Sandstone basin-floor topography to be reconstructed. The basin comprised a northern and a southern sub-basin, which were separated by a ridge, through which a trough was cut (the Coyer Trough) linking the two sub-basins during the latter stages of infilling. Data on provenance and paleocurrents suggest that the sandstones were sourced from two main feeder systems: an eastern source from the Alps fed the northern sub-basin, and a southern source fed the southern sub-basin. There is evidence of mixing of provenance in the lower parts of the southern sub-basin.Integration of the reconstructed basin-floor topography, sedimentdispersal data, and facies and stratal architectures suggests a depositional model comprising sand-rich, delta-fed submarine ramps and/or aprons whose development was strongly influenced by the basin-floor topography. The southern sub-basin initially had a steeper delta front, characterized by debris flows; this contrasted with the lower-gradient northern sub-basin. The southern sub-basin comprises approximately 800 m of thick-bedded sandstones interpreted as the deposits of sustained and possibly ponded turbidity currents. The upper part of the southern sub-basin records increased channeling and scour related to bypass of material after the basin was filled; these channels transported material northwards through the Coyer Trough, and capped the northern sub-basin. This development of the southern sub-basin is comparable to the ''fill and spill'' development of perched, intra-slope basins in the Gulf of Mexico.

Deep-water sedimentation in the Alpine Foreland Basin of SE France: New perspectives on the Grès d’Annot and related systems—an introduction

“…Following the first reinterpretation of the St Antonin conglomerates as a fan delta (Stanley 1980), the Gr~s d'Annot system is no longer considered as a classic canyon-fed submarine fan, but as a sand-rich turbidite submarine ramp fed by multiple-source fan deltas at the border of the Corsica-Sardinia massif (cf. Pickering & Hilton 1998;Joseph et al 2000;Sinclair 2000). 'Fill and spill' concepts, in conjunction with the new correlations linking the sub-basin fills (Du Fornel et al), have provided key insights into the mode of basin infilling.…”

Fill to spill stratigraphic evolution of a confined turbidite mini-basin succession, and its likely well bore expression: The Castagnola Fm, NW Italy

“…Conversely, the southern-south-eastern terminations of the Costa Grande Mb. turbidites consist of pinching and shaling out of turbidite beds (Felletti, 2002), thereby giving rise to an aggradational onlap (sensu Smith and Joseph, 2014; type 3 or 'apparent' onlap of Sinclair, 2000) with an average trajectory of less than 5°. The observed turbidite terminations styles and the position of the last documented onlap (i.e.…”

“…Ponded turbidite systems are common in a range of different geodynamic contexts (e.g. salt-withdrawal mini-basins of continental slopes in passive margins, structurally confined basins of rifted margins and foreland basin systems; Smith 2004) and are well documented from both the subsurface (McGee et al 1994;Holman and Robertson 1994;Winker 1996;Prather et al 1998;Lamers and Carmichael, 1999;Argent et al, 2000;Winker and Booth 2000), near seabed analogues (Beauboeuf and Friedman, 2000;Deptuck et al, 2012;Hay, 2012;Prather et al, 2012a, b) and outcrop (Pickering and Hiscott, 1985;Haughton, 1994;Pickering & Hilton 1998;Sinclair 2000;Tomasso 2001;Sinclair and Tomasso 2002;Amy et al, 2007;Felletti and Bersezio 2010). Flow stripping occurs when the most dilute upper part of a turbidity current suspension cloud is able to escape the basin spilling over the confining topography (Sinclair and Tomasso 2002).…”

Sedimentary filling of a wedge-top basin and relationship with the foredeep (Middle Miocene Marnoso-arenacea Formation, northern Apennines)

“…This suggests that the deposition occurred close to the source area, in the proximity of the feeding deltaslope system. In early papers (e.g., Heller and Dickinson 1985;Sinclair 2000) sand-rich deposits adjacent to a feeding delta system were termed delta-fed turbidites. Recently, Fig.…”

“…Geometric and genetic relationships between shallowmarine and deep-sea deposits are a topical issue in many papers describing both compressional (e.g., Chan and Dott 1983;Heller and Dickinson 1985;Mutti et al 2003;Sinclair 2000) and extensional settings (e.g., Falk and Dorsey 1998;Dreyer et al 1999;Young et al 2000;Piper and Normark 2001). However, such relationships are often diYcult to explore because tectonic deformation and the generally limited outcrop extension mask lateral relationships between proximal and related distal depositional settings.…”