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,
bottom loading (crustal thinning or density increase), 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 bottom loading, and 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 Hesperian mantle plumes could be at the origin
of the volcanic ridged plains.