Tectonic evolution of Juventae Chasma, Mars, and the deformational and depositional structural attributes of the four major light-toned rock exposures therein

Abstract

Juventae Chasma, a canyon peripheral to the Valles Marineris trough system, is the product of a unique merger of a Martian chaotic terrain depression and an extensional (tectonic) chasm. The chaotic terrain portion is set along a NNE-SSW axis, while a linear trough (the chasm component) is present along a WNW-ESE axis. Within the chasm are four discrete bodies of layered, light-toned rocks of sedimentary origin, Features A–D. The chaotic terrain component formed during the Early Hesperian as a result of expulsion of liquid water along pre-existing planes of weaknesses resulting from a WNW-ENE compression. The chasm component formed in response to NE-SW extension during the Middle to Late Amazonian. The light-toned Features A–D are layered at <2 m scale. A dark-toned material, previously interpreted as interstratified with the light-toned layers, is a secondary accumulation deposited after the light-toned rocks were lithified and exposed at the Martian surface. The bedding configurations within Features A, C, and D indicate eolian sand deposition; whereas a lacustrine or low-energy eolian origin is more fitting for Feature B. Features A–D also record Early Hesperian compressional events in the form of joints. Bedding joints, formed in response to release of an overburden, are also found. In addition, closed, elliptical outcrop patterns of inward dipping layers are also identified; these are either folds (structural basins) or erosional surfaces cutting three-dimensional eolian cross-beds.