The critical role of stratification in submarine channels: Implications for channelization and long runout of flows

Abstract

Channelized submarine gravity currents travel remarkable distances, transporting sediment to the distal reaches of submarine fans. However, the mechanisms by which flows can be sustained over these distances remain enigmatic. In this paper we consider two shallow water models the first assumes the flow is unstratified whilst the second uses empirical models to describe vertical stratification, which effects depth averaged mass and momentum transfer. The importance of stratification is elucidated through comparison of modeled flow dynamics. It is found that the vertically stratified model shows the best fit to field data from a channelized field-scale gravity current in the Black Sea. Moreover, the stratified flow is confined by the channel to a much greater degree than the flow in the unstratified model. However, both models fail to accurately represent flow dynamics in the distal end of the system, suggesting current empirical stratification models require improvement to accurately describe field-scale gravity currents. It also highlights the limitations of weakly stratified small-scale experiments in describing field-scale processes. The results suggest that in real-world systems stratification is likely to enable maintenance of velocity and discharge within the channel, thus facilitating sediment suspension over distances of hundreds of kilometers on low seafloor gradients. This explains how flows can travel remarkable distances and transport their sediment to the distal parts of submarine fans.

Hybrid event bed character and distribution linked to turbidite system sub‐environments: The North Apennine Gottero Sandstone (north‐west Italy)

“…Flow volume and concentration control flow run‐out distance (Mutti, ; Dorrell et al ., ) and flow interaction with the sea floor (Stevenson et al ., ), shifting the area of flow bypass and deposition basinward or landward (Mutti et al ., ), and influencing the mechanism of mud entrainment. The Gottero system contains a wide spectrum of flow types, which deposited their sediment load in different locations (Fig.…”

The inherent instability of leveed seafloor channels

“…Although the fractionation of deposited material behaves as a function of the change in channel area, , different systems may have different characteristic sediment fractionation, E (0). For example, variation in E (0) will be partially controlled by topographic constraints, such as channel meandering [ Straub et al , ] and flow stratification (mass lost overbank decreases with increasing stratification [ Dorrell et al , ]; i.e., E decreases as stratification increases). Sediment fractionation‐dependent, late stage evolution of an aggradational channel‐levee system is depicted in Figure (geometry is assumed constant).…”

A simple model for vertical profiles of velocity and suspended sediment concentration in straight and curved submarine channels

“…outer channel bend levees being consistently higher than inner channel bend levees [e.g., Pirmez and Imran, 2003]. In addition, radial material fluxes will be significantly enhanced by any flow overspill at bends, which is thought to occur frequently in submarine channels [Peakall et al, 2000;Mohrig and Buttles, 2007;Dorrell et al, 2014], and from any variations from a uniform channel bathymetry [Dorrell et al, 2013;Sumner et al, 2014]. As a consequence of these factors, a three-dimensional framework with a nonzero flux condition at bend apices is required for realistic modeling.…”