Formation of the Layered Deposits in the Valles Marineris, Mars

Thick sequences of layered deposits are found in the Valles Marineris, Mars [I-31. They exhibit fine, nearly horizontal layering, and are present as isolated plateaus of what may once have been more extensive deposits. Individual sequences of layered deposits are as thick as 5 km. We have argued previously that the morphology of the deposits is most consistent with origin in standing bodies of water [3]. The rhythmic nature of the layering, their lateral continuity, horizontality, great thickness, and stratigraphic relationships with other units in the canyons all appear most consistent with deposition in a quiet aqueous environment. If standing bodies of water existed for any significant period of time in the Valles Marineris, they were almost certainly ice-covered. Here, we examine in detail the conditions necessary for the existence of ice-covered martian paleolakes, and consider mechanisms for sediment deposition in them.