The Character and Genesis of Submarine Mass-Transport Deposits: Insights from Outcrop and 3D Seismic Data

Abstract

Extensive deep-water mass-transport deposits are observed both in slope and basin-floor settings. A detailed understanding of mass-transport deposits, in terms of emplacement processes, depositional products, and their stratigraphic and geographic distribution, is vital because they can constitute a significant portion of the stratigraphic section in deep-water settings. In addition, mass-transport deposits can play a significant role in hydrocarbon exploration, inasmuch as they can constitute seal, reservoir, and possibly source facies under the right circumstances. Different data types bring to light different aspects of mass-transport deposits. This paper focuses on insights derived from seismic and outcrop data. Overall geometries and architecture of mass-transport deposits are readily observable in 3D seismic data; however, features below seismic resolution that are vital for process and lithologic understanding need to be observed in outcrop. Integrating observations across a broad range of scales by linking seismic and outcrop observations constitutes an effective way of improving our understanding of when and where mass-transport deposits are likely to form. In addition, this linkage sheds light on details of internal architecture that commonly characterizes these deposits. Mass-transport deposits can comprise sheets, lobes, and channels fills, and reach 150 m or more in thickness. Greater thicknesses are observed where successive flows are amalgamated. This paper documents both internal architectural/stratigraphic as well as external geomorphic attributes of such deposits, as expressed in outcrop and imaged by 3D seismic data. Recognition of mass-transport deposits in outcrop is based on identification of bedding deformed by synsedimentary processes, with deformation ranging from minimal redistribution of large slide blocks to complete disaggregation typical of debris-flow deposits. On seismic data, mass-transport deposits can be recognized by certain geomorphologic as well as stratigraphic distinguishing characteristics: basal linear grooved and scoured surfaces, hummocky relief at the top, and internal chaotic to transparent seismic facies, with internal thrust faulting common.

Seismic expression of depositional elements associated with a strongly progradational shelf margin: northern Santos Basin, southeastern Brazil

“…The sandy turbidites of the Eocene were previously recognized as good reservoirs (Moreira & Carminatti, 2004;Chang et al, 2008), and oil shows associated to these deposits were detected in some wells. However, Moreira & Carminatti (2004) do not consider the MTDs as good seals due to the presence of compressive structures such as thrust faults that reduce sealing capacity (e.g., Bull et al, 2009;Posamentier & Martinsen, 2011;Alves et al, 2014;Fig. 10).…”

“…Internally, this facies is strongly affected by sin-sedimentary deformation, more typically reverse faults pointing to a compressive regime ( Fig. 10; e.g., Posamentier & Kolla, 2003;Posamentier & Martinsen, 2011). Other compressive structures, such as open folds (Fig.…”

Role of sea-level change in deep water deposition along a carbonate shelf margin, Early and Middle Permian, Delaware Basin: implications for reservoir characterization

“…Mass-transport deposits (MTD) result from gravity-driven downslope movement of massive sediment particles where the main sediment support mechanism is non-fluid turbulence (thus excluding turbidity currents, fluidized flows, lique- fied flows, and other non-cohesive, frictional flows) (Lowe 1979;Nardin 1979;Cook & Mullins 1983;Mulder & Alexander 2001;Posamentier & Martinsen 2011). This kind of deposition generally occurred as a result of decrease of accommodation due to rapid sea level fall, hydraulic degradation and over-steepening of the shelf margin, oversaturation of unconsolidated slope deposits, and winnowing of sediment by strong bottom currents (Wiggins & Harris 1985;Gawloski 1986;Saller et al 1989).…”

“…High-density turbidity currents were defined by different criteria including current density and sediment concentration (sediment by weight and solids by volume) (Kuenen 1966;Lowe 1982;Shanmugam 1996;Posamentier & Martinsen 2011). The northwestern slope of the Delaware Basin exhibits plenty of amalgamated/isolated channels (Fig.…”

Fabric Development and Pore-Throat Reduction in a Mass-Transport Deposit in the Jubilee Gas Field, Eastern Gulf of Mexico: Consequences for the Sealing Capacity of MTDs

“…Although, for obvious industrial reasons, turbidites have received the most attention during the past decades, the more recent acquisition of high-resolution three-dimensional (3-D) seismic data has shown that many slope and abyssal systems comprise a very significant portion of MTCs. In some settings around the world, up to 70-90% of the entire slope and deepwater stratigraphic record is composed of MTCs and associated deposits (Canals et al, 2004;Newton et al, 2004;Moscardelli, 2007;Madof et al, 2009;Beaubouef and Abreu, 2010;Posamentier and Martinsen, 2011). Although numerous geoscientists use the terms MTDs and MTCs interchangeably, in this study we define a MTC as a depositional architectural complex comprised of several coeval or closely chronological-and genetically-related masstransport deposits (MTDs)-i.e.…”