This highly tectonized terrain (meaning it possesses many faults) has its low-lying areas filled with some form of younger material. This particular fill is what geologists call “embayment.”
This observation helps scientists unravel the relative timing of the emplacement of the younger material and the numerous tectonic faults that run through this area.
Written by: HiRISE Science Team (audio: Tre Gibbs) (22 April 2015)
More info and image formats at http://hirise.lpl.arizona.edu/ESP_039658_1425
Image: NASA/JPL/University of Arizona