Structural characterization of Juventae Chasma, Mars, and its four light-toned stratified rock occurrences

Juventae Chasma, an isolated trough NE of Valles Marineris, hosts four large bodies of layered, light-toned, sedimentary rocks that we refer to as Features A, B, C, and D. Juventae Chasma is a merger of a chaos and a chasm. However, the time and progress of the events leading to the current configuration of the chasm and the light-toned rocks are unknown. Moreover, the depositional processes forming the light-toned rocks are also uncertain. This study uses high-resolution panchromatic images (HiRISE and CTX) and DEMs derived from HiRISE stereo-pairs. The objectives are: (a) to assess the progression of events leading to the current configuration of the chasm, (b) to identify any signatures of the depositional mechanism within the Features A-D, and (c) to evaluate the structural attributes of the Features A-D.

Key results are: (1) The chaotic terrain in the N of Juventae Chasma formed due to the expulsion (catastrophic and/or non-catastrophic) of liquid water along pre-existing planes of weaknesses created by conjugate strike-slip faults resulting from a WNW-ENE compression during Early Hesperian. The exact timing and duration of the chaos formation is uncertain, and could have happened at any time following this compressional event. (2) The canyon in the S of Juventae Chasma is related to extensional faulting in response to NE-SW extension during Middle/Late Amazonian. (3) The light-toned Features A-D consist of fine layers (thickness <1.5 m). The dark-toned material, often interpreted as interstratified with the light-toned layers is actually a secondary deposit that accumulated after the light-toned Features were deposited and lithified. (4) Bedding configuration in Features A, C, and D represent cross-beds and bounding surfaces (Fig. 1). The meter-scale cross-beds, absence of fluvial features, and a uniformity of materials suggest these to be eolian deposits. (5) The light-toned Features A-D show brittle deformations, mostly joints—some related to the Early Hesperian compressional event, and some formed in response to release of an earlier overburden-induced stress. (6) Closed elliptical outcrop patterns of inward dipping layers are also identified and are either folds (structural basins) or erosional surfaces cutting three-dimensional cross-beds.