Fault of Jus

The sharpness and quality of HiRISE images allows geologists to work out the detailed geometry and sequence of events that have shaped the landscape. For example, this area shows exposures of light- and dark-toned layers of rock that have been faulted and folded. These rocks formed out of sedimentary deposits that originally accumulated in thick horizontal sequences, like a layer cake.

These layers have since been tilted on-end and eroded, exposing the sequence of layers that we now see at the surface. A prominent dark layer extends through the center of the scene from the upper right to the lower left of the image. This dark layer is discontinuous and offset along a fault.

The thin grey zone that extends from the upper left to the lower right of the image delineates the fault plane. This fault was originally a thrust, or compressional fault, that formed prior to the aforementioned tilting event. Tilting of this fault and the surrounding rock reveals a series of drag folds adjacent to the fault plane. These drag folds formed as the layered rock bent in response to friction along the fault plane as the thrust fault formed, prior to the tilting event. This fault offsets the dark layer by a maximum of 70-75 m. Smaller secondary folds and faults are also visible in this scene. The smallest resolved fault offset of an individual rock layer is 1-1.5 m. Also visible in this image are numerous small 4-10-m-diameter impact craters that are surrounded by ejecta of meter-scale boulders.