Structural study of graben within the Margaritifer Terra region of Mars

Abstract

The surface of Mars preserves a variety of structural and geomorphic features such as wrinkle ridges, graben, lobate scarps, impact basins, paleochannels etc., which owe their origin to endogenic processes of deformation as well as meteorite impacts. Graben, which form in extensional stress regimes, are one of the most common structural features identified on these planetary bodies. Many graben are observed in the Margaritifer Terra, a Noachian (4.1 Ga to 3.7 Ga) highland terrain in the southern hemisphere of Mars; but a detailed structural study of these graben have not been carried out so far. The diverse geomorphology of these graben such as their orientation, planform and disposition make the region interesting for structural geological studies. With an aim to unveil the causes behind the formation of these graben, detailed morphometric analyses, estimation of maximum displacement of the faults, and extension across them (ranging between ∼0.3 and ∼0.8 km), as well as age estimation (minimum ∼1 Ga to maximum ∼3.8 Ga) and correlation with the stratigraphic units are carried out on eleven prominent graben in the Margaritifer Terra. The graben belong to two age clusters: 1) late Noachian–early Hesperian and 2) Amazonian. The age-depth correlation, proximity to chaos and floor-fractured craters, absence of any dominant geographic trend and presence of circular graben together indicate that the graben were formed due to dike emplacement in the area in two distinct phases separated by about 2 Ga. Older graben were formed above dike tops at greater depth (>50 km below the surface) while dikes below the younger graben reached shallower levels (∼4 km below the surface) below the surface. The intrusive activities are local to the Margaritifer Terra region and were possibly not caused by Tharsis and Valles Marineris related deformation.