Submarine mass‐transport facies: new perspectives on flow processes from cores on the eastern North American margin

Abstract

No comprehensive scheme yet exists to describe the depositional products of submarine sediment failures at the scale of piston cores, resulting in misinterpretation of failure deposits and overuse of the genetic term ‘debris flow’. Ninety‐nine sediment cores (0·5 to 20 m in length), from offshore eastern Canada and the Gulf of Mexico, are used to propose a descriptive sedimentary facies scheme with genetic implications for mass‐transport deposits. Seven facies are distinguished: (i) allochthonous stratified sediment; (ii) distorted stratified sediment; (iii) clast‐supported hard‐mud‐clast conglomerate; (iv) matrix‐supported mud‐clast conglomerate; (v) thin mud‐clast conglomerate (<0·8 m thick); (vi) diamicton; and (vii) sorted sand‐gravel deposits (≥0·05 m thick). Seven genetic types of deposits are recognized. (i) Slumping of coherent sediment blocks (facies I). (ii) Slump and slide deposits (facies I and II). (iii) Debris‐avalanche deposits (hard sediment of facies I and II overlain by facies III). (iv) Low‐viscosity or large‐scale, high‐viscosity, cohesive debris flow deposits (facies IV, may have I, II, and III). (v) Very low‐viscosity debris flow deposits (facies V). (vi) Cohesionless debris flow deposits (facies VI). (vii) High‐density turbidity currents (facies VII). Vertical transitions between the genetic types were analysed by Markov chain analysis. Although sedimentological transitions are inferred between deposits of slides and cohesive debris flows, their spatial distribution indicates that a cohesive debris flow forms principally in the initial stages of a sediment failure, suggesting that transformation depends mostly on the strength of the sediments. A genetic link is suggested for cohesionless debris flow deposits, which originate from the disintegration of sandy sediment on the upper continental slope, and the closely related turbidity current deposits. Debris avalanches are common in sedimentary marine environments with steep slopes (>10°). In many cases, geometrical and seismic characteristics of debris avalanche, slide and debris flow are similar, requiring core data to verify transport process.

Owen Ridge deep-water submarine landslides: implications for tsunami hazard along the Oman coast

“…Because the speed of the failed mass strongly affects the amplitude of the out-going wave (Trifunac and Todorovska, 2002), it is important to determine the kinematics of the landslide, i.e., whether the mass movement is a slump or a debris flow. Based solely on multibeam bathymetry and echosounder data, it is ambiguous to solve the latter problem as mass movement type is usually assessed by rigorous core analyses (Mulder and Cochonat, 1996;McAdoo et al, 2000;Tripsanas et al, 2008). Nevertheless, mapping the architecture of sediment failures using subsurface data provides fundamental constraints on numerical models of tsunami generation (Tappin, 2010).…”

Are great Cascadia earthquakes recorded in the sedimentary records from small forearc lakes?

“…Turbidites can also be ( ( very complex resulting in classic Bouma sequences (Bouma, 1962) or multi-pulsed or stacked turbidites (e.g. Tripsanas et al, 2008;Gutiérrez-Pastor et al, 2013). Unsorted coarse material may sometimes precede gravity flow deposits, resulting in a linked debrite when a debris-flow deposit is overlain by graded sediment as finer material settles out of suspension (Tripsanas et al, 2008).…”

“…Tripsanas et al, 2008;Gutiérrez-Pastor et al, 2013). Unsorted coarse material may sometimes precede gravity flow deposits, resulting in a linked debrite when a debris-flow deposit is overlain by graded sediment as finer material settles out of suspension (Tripsanas et al, 2008). Wide areal extent and thickness (and therefore mass) of density flow deposits have been used as criteria along with sedimentological criteria to differentiate earthquake-generated deposits, however it is difficult to infer earthquake triggering without additional information.…”

Investigations on the Peach 4 Debrite, a Late Pleistocene Mass Movement on the Northwest British Continental Margin

“…Oscillating mean grain size and sorting values (see Fig. 3), supports a debris flow hypothesis for the formation of this unit; potentially through as succession of slurries or as a low-viscosity cohesive debris flow (see Tripsanas et al 2008). …”