Thrust faults along the dichotomy boundary in the eastern hemisphere of Mars

[1] Mars Orbiter Laser Altimetry (MOLA) data have been used to characterize lobate scarps along the dichotomy boundary in the eastern hemisphere of Mars. These structures are the surface expression of thrust faulting of the southern highlands. Displacement on the thrust faults is generally less than 1 km except in the case of the Amenthes Rupes thrust fault, where the maximum displacement is on the order of 3 km. The ratio of maximum displacement to fault length g of the population of thrust faults is 6.2 10 3 (n = 26), consistent with previous estimates for Martian thrust faults based on photoclinometrically derived topography, and other planetary thrust fault populations. Thrust faulting is roughly coincident with Late Noachian to Early Hesperian fracturing and normal faulting along the dichotomy boundary. This suggests that the formation of the present-day dichotomy boundary involved compressional and extensional deformation. The long-wavelength topography suggests that the dichotomy boundary in the eastern hemisphere may have been formed by flexure of the southern highlands lithosphere. Lithospheric flexure alone cannot account for the thrust faulting of the highlands along the dichotomy boundary. A combination of stresses due to bending, erosion, and global contraction may have formed the lobate scarp thrust faults.