Plume-Induced Flood Basalts on Hesperian Mars: An Investigation of Hesperia Planum

Abstract

Hesperian Mars was characterized by a unique style of geodynamic activity that left crucial volcano-tectonic records in the form of extensive flood lavas covered by wrinkle ridges. Yet, little is known about the context of their formation. Here, we perform a tectonic and geophysical investigation of Hesperia Planum, a 1700-km- diameter volcanic plain covered by wrinkle ridges. Our tectonic analysis reveals that the planum has the highest density of wrinkle ridges on the planet and a characteristic compressional peak strain of about 3.20×10-3, almost 2 times larger than typical Hesperian compressional strains. We invert gravity and topography data and find that simple crustal loading and volcanism cannot explain the tectonic record. An additional source of deformation is thus required. We demonstrate that a loading sequence of plume-induced uplift, volcanism, and subsidence, following an evolutionary path similar to flood basalt provinces on Earth better fits the observations. This plume model is able to explain the peak strain, crustal thinning, and low relief of Hesperia Planum. The inferred plume head size (~1400 km) and temperature anomaly (~320 K) are consistent with large terrestrial plumes. Based on a fit to the tectonic record, we determine a plume center location that correlates with a cluster of wrinkle ridges, local crustal thinning, and a circular magnetic low, where the latter could be the result of a thermal demagnetization of the lithosphere in the presence of the ascending plume. Our analysis suggests that scattered mantle plumes could be at the origin of Hesperia Planum and other late Noachian to early Hesperian volcanic provinces within the highlands.