Evidence for Folding of Layered Terrains in Candor Chasma, Mars

Milliken, Ralph E.¹, John Grotzinger² (1) Jet Propulsion Laboratory/California Institute of Technology, Pasadena, CA (2) California Institute of Technology, Pasadena, CA

The western region of Candor Chasma, a subsection of the Valles Marineris canyon system on Mars, contains layered deposits that exhibit fold structures with morphologies similar to anticline-syncline pairs found on Earth. The folds are 1-3 km in length with wavelengths on the order of hundreds of meters. High-resolution images reveal bedding planes spaced ~10-100 m apart and layers of alternating high and low albedo. When folded, these layers exhibit dip angles that range from sub-horizontal to nearly vertical in the limbs, with east-west trending fold axes. Folds also appear to plunge at gentle to steep angles and are commonly observed near the base of the canyon walls, which have a height on the order of several kilometers. In addition to the folds, several structural domes of layered materials are observed in adjacent canyons. Both folds and domes can have strongly disharmonic geometries. The materials that comprise the folds are morphologically similar to nearby deposits of flat lying, light-toned materials determined from orbital near-infrared reflectance measurements to be rich in sulfate salts. Upcoming high-spatial resolution reflectance spectra may help determine if light-toned layers within the folds are also sulfate-rich. We will present our findings of the physical, chemical, and structural properties of these layered materials as derived from datasets acquired by multiple spacecraft in order to determine the geologic origin of these fold and dome features. Several possible origins will be discussed: slumping or flow of layered bedrock down the canyon walls, localized tectonic activity, and salt diapirism.