Sedimentary rocks of early Mars

Layered and massive outcrops on Mars, some as thick as 4 kilometers, displa y the geomorphic attributes and stratigraphic relations of sedimentary rock . Repeated beds in some locations imply a dynamic depositional environment during early martian history. Subaerial (such as eolian, impact, and volcan iclastic) and subaqueous processes may have contributed to the formation of the layers. Affinity for impact craters suggests dominance of lacustrine d eposition; alternatively, the materials were deposited in a dry, subaerial setting in which atmospheric density, and variations thereof mimic a subaqu eous depositional environment. The source regions and transport paths for t he materials are not preserved.