Dating long thrust systems on Mercury: New clues on the thermal evolution
of the planet
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Abstract
The global tectonics of Mercury is dominated by contractional features mainly represented by lobate scarps, high
relief ridges, and wrinkle ridges. These structures are the expression of thrust faults and are linear or arcuate
features widely distributed on Mercury. Locally, these structures are arranged in long systems characterized by a
preferential orientation and non-random spatial distribution. In this work we identified five thrust systems,
generally longer than 1000 km. They were named after the main structure or crater encompassed by the system
as: Thakur, Victoria, Villa Lobos, Al-Hamadhani, and Enterprise. In order to gain clues about their formation, we
dated them using the buffered crater counting technique, which can be applied to derive the ages of linear
landforms such as faults, ridges and channels. To estimate the absolute age for the end of the thrust system’s
activity, we applied both Le Feuvre and Wieczorek Production Function and Neukum Production Functions.
Moreover, to further confirm the results obtained with the buffered crater counting method, the classic stratigraphic
approach has been adopted, in which a faulted and an unfaulted craters were dated for each system. The
results gave consistent ages and suggested that the most movements along major structures all over Mercury most
likely ended at about 3.6–3.8 Ga. This gives new clues to better understand the tectonics of the planet and,
therefore, its thermal evolution. Indeed, the early occurrence of tectonic activity in the planet’s history, well
before than predicted by the thermophysical models, coupled with the orientation and spatial distribution of the
thrust systems, suggests that other processes beside global contraction, like mantle downwelling or tidal despinning,
could have contributed to the first stage of the planet’s history.
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