How Fast Can Minibasins Translate Down a Slope? Observations from 2D Numerical Models

Abstract

Minibasins are important features in salt-bearing basins and are abundant in salt-detached continental slopes where the salt and the overlying sedimentary cover (including minibasins) undergo seaward translation due to gravity. One question which is relevant for understanding the structural evolution of salt-detached slopes is what controls the translation velocity of the salt layer and of overlying minibasins. The aim of this study is three-fold: 1) to compare minibasin downslope translation velocity with salt translation velocity; 2) to understand what controls minibasin translation velocity and 3) to understand how minibasins translating at different velocities can kinematically interact and modify strain patterns around them. To address these questions, we present a 2D numerical modelling study. In addition to parameters that control salt velocity, we show that minibasin thickness is the main factor controlling minibasin velocity in the numerical models. If the minibasin is far from the base-of-salt, its velocity can be estimated by a 1D analytical solution of salt flowing on a slope. Specifically, thicker minibasins translate slower than thinner minibasins. If the minibasin is close to the base-of-salt, viscous drag slows it further, and the numerical results deviate from the 1D analytical solution. Finally, we assess how several minibasins of differing thicknesses and translation velocities, may diverge or converge as they translate downslope, resulting in varying strain patterns around them. Findings from our numerical modelling provide additional conceptual understanding of structural evolution of salt-detached continental slopes that have significant implications for understanding minibasin behaviour, and interpreting strain patterns around them.