This region of eastern Meridiani shows a fairly smooth texture where we can see the filling-in of small craters with aeolian (wind deposited) sand.
The sand is likely basaltic in origin. Some of the sand blown by the wind has eroded the local terrain, whereas other deposits have become trapped within small craters. The bedrock contains phyllosilicates (clay minerals), which form in the presence of water. Phyllosilicates have been detected in higher concentrations in other areas of Mars such as Mawrth Vallis and Nili Fossae, but detections of lesser abundance have been noticed in Meridiani as well.
Written by: Jennifer Griffes (3 August 2007)
More info and image formats at http://hirise.lpl.arizona.edu/PSP_004315_1815
Image: NASA/JPL/University of Arizona