Development of banded terrain in an active salt diapir: potential analog to Mars

Abstract

Banded terrain is a planetary enigma that may be associated with salt diapirs. We study such features in Mount Sedom diapir, which is one of the few places on Earth where rock-salt is partly exposed and well-preserved because of the extreme aridity of its setting. The relief and surface features of the diapir generally reflect its parent-rock geological structure, stratigraphy and lithology on one hand, and recent erosion and dissolution on the other hand. We show that these features are commonly aligned along parallel strike-oriented lines forming banded terrain. We measure the surface deformation, demonstrating an absolute uplift rate reaching ~7–8 mm/yr. The extruded volume rate of Mt. Sedom bedrock is estimated to be 48,000 ± 12,000 m3/yr. Subtracting erosion and dissolution, the ridge mass increases by 70,000 ± 20,000 metric tons per year, inducing a young (Holocene) and steep landscape. We compare surface landforms with subsurface geology exposed in caves. They include lines of sliding faults, dissolution furrows, sinkholes of dissolution and collapse origin, karstic shafts, and an irregular disrupted drainage system dominated by blind valleys. The diapir rock-salt is covered by residual caprock, in its turn partly overlain by less consolidated hardly-soluble sediments and gravels. Terraces of abrasion and regressing lakeshore of the Dead Sea appear along the ridge margins. Exposed salt outcrops are relatively rare and undergo rapid dissolution, demonstrated by karst features which range from ponors to the longest salt caves known globally. The extreme solubility of the underlying salt influences the surface and subsurface landscape, inducing high permeability along fractures, and promoting runoff capture into the underlying salt. All studied landforms contribute to the banded relief of Mount Sedom, which can be used to analyze banded or closely-related honeycomb terrain across other terrestrial and planetary diapirs.