Gravimetric and Flexural Analysis of the Tharsis Province, Equatorial Region of Mars

Análisis Gravimétrico y Flexural de la Provincia de Tharsis, Región Ecuatorial de Marte

Abstract

The lithospheric flexure under the load of the volcanic structures located in the Tharsis region was analyzed, departing from the elaboration of a set of gravimetric maps which subsequently allowed to propose several geological models of the crustal structure beneath the mega-shield volcanoes present there. The isostatic compensation degree for each of the loads was studied according to their isostatic anomalies, determining that the compensation system in the region can’t be explained by means of local isostasy mechanisms. Through the application of the elastic flexure theory flexural models were proposed, supposing an anisotropic mechanical behavior of the lithosphere, to obtain the variations of the effective elastic thickness along the suggested profiles. The mean elastic thickness estimated over the preferential orientation of the structures was obtained with a value of 127 km, concluding that they were formed on a considerably rigid lithosphere. From these results, it was determined that, in its current static state, the mechanical strength of the plate decreases from North to South. A mechanical anisotropy zone was interpreted in the Southeastern region of Tharsis, and was manifested mainly due to the rheological processes that intervened in the past rather than due to the magnitude of the present loads. From an isostatic standpoint, this area with the highest degree of anisotropy, could be representative of the most recent volcanic activity within the evolutionary history of the province.