Relationships between shelf-edge trajectories and sediment dispersal along depositional dip and strike: a different approach to sequence stratigraphy

Abstract

Analysis of shelf-edge trajectories in prograding successions from o¡shore Norway, Brazil,Venezuela and West Africa reveals systematic changes in facies associations along the depositional dip.These changes occur in conjunction with the relative sea-level change, sediment supply, inclination of the substratum and the relief of the margin. Flat and ascending trajectories generally result in an accumulation of £uvial and shallow marine sediments in the topset segment. Descending trajectories will generally result in erosion and bypass of the topset segment and deposition of basin £oor fans. An investigation of incised valley ¢lls reveals multiple stages of ¢lling that can be linked to distinct phases of deepwater fan deposition and to the overall evolution of the margin. In the case of high sediment supply, like the Neogene Niger and Orinoco deltas, basin £oor fans may develop systematically even under ascending trajectory styles. In traditional sequence stratigraphic thinking, this would imply the deposition of basin £oor fans during a period of relative sea-level highstand. Facies associations and sequence development also vary along the depositional strike.The width and gradient of the shelf and slope show considerable variations from south to north along the Brazilian continental margin during the Cenozoic. During the same time interval, the continental shelf may display high or low accommodation conditions, and the resulting stacking patterns and facies associations may be utilized to reconstruct palaeogeography and for prediction of lithology. Application of the trajectory concept thus reveals nuances in the rock record that would be lost by the application of traditional sequence stratigraphic work procedures. At the same time, the methodology simpli¢es the interpretation in that less importance is placed on interpretation and labelling of surface boundaries and systems tracts.Given su⁄cient sediment supply and water depths, the basinward progradation of coastal prisms and clastic wedges

Clinoforms and clinoform systems: Review and dynamic classification scheme for shorelines, subaqueous deltas, shelf edges and continental margins

“…As previously pointed out, although both shelf-edge and continental-margin clinoforms are developed at the outer edge of a bathymetric "shelf" or "plateau", several authors differentiate these two categories on the basis that they correspond to statistically different clinoforms, associated to distinct structural styles and bathymetry Henriksen et al, 2011;Patruno et al, 2015a). Diagnostic characteristics for continental-margin clinoforms over shelfedge clinoforms include significantly slower progradation rate, lower progradation/aggradation ratios (Fig.…”

“…Sloping depositional units occur at scales ranging from ripple-(centimetres), dune-and bar-foresets (decimetres to metres), delta and shoreface slopes (1-100 m) and up to sloping units formed by accretion of shelf edges (100's m) and continental margins (> 1000 m) (Larue and Martinez, 1989;Thorne, 1995;Henriksen et al, 2011) (Figs. 1, 2).…”

“…In cases of very high sediment supply, however, deep-water sand transport may take place even during normal regressions and/or highstands, through un-channellized slumping, mass transport complexes and low-density turbidites Steel, 2006, 2009;Steel et al, 2008;Kertznus and Kneller, 2009;Henriksen et al, 2011;Dixon et al, 2012aDixon et al, , 2012b. A key example in this respect is the Neogene lacustrine shelf-edge scale clinoform succession in the Pannonian shelf-edge lacustrine basins Sztanó et al, 2013), where each phase of rising base-level corresponded to a time of climate-driven high sediment supply, when large volumes of sediments bypassed the aggrading topsets onto the slope and basin-floor.…”

Contrasting slope channel styles on a prograding mud-prone margin

“…Weimer and Davies, 1996;Helland-Hansen and Hampson, 2009;Kertznus and Kneller, 2009;Henriksen et al, 2010).…”

Shelf-edge trajectories and stratal stacking patterns: Their sequence-stratigraphic significance and relation to styles of deep-water sedimentation and amount of deep-water sandstone

“…It therefore offers an objective and dynamic approach to investigate the stratigraphy and sedimentology of sedimentary basins (Steel and Olsen, 2002;Hampson et al, 2009;Helland-Hansen and Hampson, 2009;Henriksen et al, 2009). In the past 15 yr or so, many authors have used concepts of shelf-edge trajectories to investigate the stratigraphy and sedimentology of deep-water siliciclastic systems (e.g., Plink-Björklund et al, 2001;PlinkBjörklund and Steel, 2002;Steel and Olsen, 2002;Pyles and Slatt, 2007;Uroza and Steel, 2008;Henriksen et al, 2011;Pyles et al, 2011). Previous work has enhanced our understanding of many aspects of shelf-edge trajectories, including trajectorial behavior, controlling factors, and relation to deep-water sands and to sediment-volume partitioning (e.g., Steel and Olsen, 2002;Carvajal and Steel, 2006;Pyles and Slatt, 2007;Hampson et al, 2009;Helland-Hansen and Hampson, 2009;Henriksen et al, 2011;Pyles et al, 2011).…”