Fluid Expulsion in Terrestrial Sedimentary Basins: A process providing potential analogs for giant polygons and mounds in the martian lowlands

Abstract

On Earth, burial of fine-grained sediments in offshore passive margins (e.g., underwater fans and deltas) commonly results in fluid expulsion features including large-scale polygonal fractures, mud volcanoes, and pockmarks. Comparison of resulting offshore polygons and mud volcanoes with giant polygons and high-albedo mounds in the Chryse–Acidalia region of Mars shows the terrestrial and martian features to be similar in size, morphology, geologic context, and general co-occurrence within the same basin. These similarities suggest that the process of terrestrial fluid expulsion may provide an analog that could link the giant polygons and mounds in Chryse and Acidalia to a single process. Moreover, while the terrestrial offshore polygons and mud volcanoes commonly develop in the same basins, these features do not necessarily occur in exactly the same locations within those basins, as they are independent responses to compaction and dewatering. Thus, the fluid expulsion analog does not require that the martian giant polygons and mounds have identical distributions. This is the situation in Chryse and Acidalia where the giant polygons and mounds are extensively developed and generally have overlapping distributions, but where each set of features may occur in places without the other. This fluid expulsion analog is enhanced by the fact that giant polygons and mounds in Chryse and Acidalia cooccur in a regional sense and in a geologic setting that is consistent with a fluid expulsion model of formation. Implications of this analog may impact our view of the role of water in the depositional history of the martian lowlands.