Differential subsidence and rebound in response to changes in water loading on Mars: Possible effects on the geometry of ancient shorelines

If large liquid or solid water bodies existed in the past in Martian basins such as Argyre, Hellas, and the northern lowland plains, they would have represented massive surficial loads. Earth analogs suggest that the magnitudes of crustal displacements related to water loading and unloading would have varied spatially within and around affected basins. It is likely that the effects of bathymetric irregularities on lithospheric flexure would have caused shoreline areas proximal to deep regions to be depressed (and, subsequently, to rebound) to a greater extent than shoreline areas located near shallow regions. Crustal and mantle inhomogeneities would have likely further contributed to spatial variation in water-related subsidence and rebound. Simple two-dimensional elastic flexure models suggest that Martian shoreline features of common age and formed in association with a large ancient water body could vary in elevation today by hundreds of meters as a result of these differential effects. Examples of similar shoreline offsets on Earth suggest that sets of Martian strandline features will reflect the changing nature of loading through time.