External signal preservation in halokinetic stratigraphy: A Discrete Element Modeling (DEM) approach

Subsurface salt movement in the absence of external tectonic forces can affect contemporaneous sediment deposition, mask allocyclic signals, and can deform older strata. We use a Discrete Element Model to better understand salt-related modification of a sedimentary sequence with an increasing sedimentation rate. This permits quantification of thinning rates and analysis of the lateral extent of syn-kinematic layers. Results show realistic evolution of salt-related faults, defining two salt-withdrawal basins, beyond which strata are undeformed. Thinning of stratigraphy is four times greater between the salt flank and crest than between the undeformed zone and flank, confirming an intense zone of halokinetic modulation adjacent to the diapir. Early slowly-aggrading layers are isolated within the salt-withdrawal basin and strongly influenced by salt growth, whereas later quickly-aggrading layers are more laterally extensive, matching inferences made from subsurface and outcrop data. Halokinetic modulation reduces up-stratigraphy, mirroring observations around the Pierce diapirs, UK North Sea. Our DEM provides quantitative insights into the dynamic interplay of halokinetic and allocyclic controls on salt-stratigraphic relationships.