Fluvial sediments, accumulations of remains
from boulder disintegration or volcanic ash ?
Apart from the detected stratified
deposits in the delta or in remnants of it, apparently stratified deposits
were found on the previous path of the rover along the distinctive linear
elevation between or downward the massive ultramafic rocks in the elevation.
An identification has not yet been successful.
The first stratified deposits were probably seen at sol 155-158. Other amazing sightings were made at sol 168-169 and sol 173-176: