Ice-rich landforms of the southern mid-latitudes of Mars: A case study in Nereidum Montes

Abstract

Mapping of Viscous Flow Features (VFFs), a general grouping of ice-rich flow features that includes Lobate Debris Aprons (LDA), Concentric Crater Fill (CCF), Lineated Valley Flow (LVF), small lobate flows (i.e., glacier-like flows, or GLFs), and arcuate ridges, in the southern hemisphere of Mars shows a dense concentration in Nereidum Montes, along the northern rim of Argyre basin. Further mapping within a subregion in northwest Nereidum Montes (45.3°–48.5° S, 307°–312° E) shows a large number of well-preserved VFFs and ice-rich mantling deposits. Processed SHARAD data across a VFF within the region indicates that it is composed of nearly pure water ice.Model ages obtained from crater counts and their associated size-frequency distributions (SFDs) on both ice-rich mantling deposits and small lobate VFFs suggest that the deposits stabilized several to tens of Ma ago in the Late Amazonian Epoch, and that small lobate VFFs likely formed due to the mobilization of mantling deposits. SFD for a larger VFF shows a model age of 100 s of Ma, consistent with ages for LDAs in eastern Hellas. Deposition of ice in Nereidum Montes that led to the formation of VFFs likely occurred during periods of high obliquity in the Late Amazonian.Our results show that VFFs have more complete and diverse preservation states in Nereidum Montes than similar features in other regions on Mars. This region contains uniquely well-preserved mantling deposits above arcuate ridges and beyond the margins of lobate VFFs and gully aprons. This key observation ties arcuate ridges to the flow of mantling deposits, part of a continuum model for mid-latitude ice-rich landforms.