Gravity-driven fold-thrust belt at the Martian dichotomy

The origin and evolution of the Martian dichotomy is one of the most enigmatic topics in Mars geological history. Its morphological variations suggest how it undergone different geological events, which reshaped the dichotomy differently. The eastern dichotomy, in the Nilosyrtis Mensae, is the only location where there is clear evidence of extensional structures in the highlands and parallel compressional structures in the adjacent southern lowlands. Both are roughly aligned parallel to the dichotomy and their origins are still debated. Here, we investigate the hypothesis that these faults are linked to gravity-driven deformation, occurred during the Late Noachian – Early Hesperian. Remote sensing geological mapping, integrated with 2D kinematic and numerical modeling, supports the possibility that extension in the highlands and along the dichotomy is kinematically linked to compression ∼800 km in the southern lowlands. The link occurs through a common basal detachment, which developed from the hard-link between a shallower frictional detachment in the highlands and a deeper viscous detachment in the lowlands. This hypothesis also provides insights into the origin and evolution of both the dichotomy and the lowlands, supporting the hypothesis of a giant Borealis northern impact. Such an impact promoted the formation of a magma pond followed by precipitation of evaporites from an ancient short-lasting shallow hypersaline sea, which was later reorganized by subsequent impacts and buried beneath volcanic deposits.