Conundrums in loading-driven salt movement

摘要

Salt evacuation and rise can be driven by differential loading. Even less-dense (siliciclastic) overburden can subside with adequate differences in pressure head due to lateral variations in overburden density and/or thickness. Although the base of the thickest load sinks into salt, the top remains a topographic high so that further sedimentation in the same area is unlikely and subsidence should cease. Yet there are numerous examples where subsidence of less-dense sediment has continued in the absence of accepted mechanisms such as extension or contraction.Here I summarize the theoretical framework and relevant analog and numerical models before addressing several related conundrums in our understanding of loading-driven salt movement. First, how do minibasins less dense than salt sink enough to accumulate more sediment and thereby keep subsiding? Second, what happens when the overburden thins in the direction opposite to the top-salt dip, as on the flank of any minibasin? I then offer some thoughts on possible solutions and suggest that further research is needed to solve these problems.