Geological mapping and structural analysis of the Michelangelo (H-12) quadrangle of Mercury

Geological cartography and structural analysis are essential for understanding Mercury’s geological history and tectonic processes. This work focuses on the Michelangelo quadrangle (H-12), located at latitudes 22.5°S-65°S and longitudes 180°E-270°E. We present the preliminary results derived from the photointerpretation of the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) Mercury Dual Imaging System (MDIS) imagery. The first geological map of this quadrangle was produced by [1] at 1:5M scale using Mariner 10 data. The Authors identified and mapped five classes of craters and four main plain units. The present study is a contribution to the 1:3M geological map series, planned to identify targets to be observed at high resolution during the ESA-JAXA BepiColombo mission [2]. Geologic contacts and linear features were drawn at a mapping scale between 1:300,000 and 1:600,000.

We mapped tectonic structures and geological contacts using the MDIS derived basemaps, with an average resolution of 166 m/pixel. Linear features are subdivided into large craters (crater rim diameter > 20 km), small craters (5 km < crater rim diameter < 20 km), subdued or buried craters, certain or uncertain thrusts, certain or uncertain faults, wrinkle ridges and irregular pits. Geological contacts, mapped as certain or approximate, delimit the geological units grouped into three classes of crater materials (c1-c3) based on degradation degree, and plains (smooth, intermediate and intercrater plains).

We identified two main regional thrust systems with a NW-SE strike. The presence of old impact basins influenced the arrangement of faults because of the frequent reactivation of crater rims. Beethoven basin (20.8°S–236.1°E) and Vincente-Yakovlev basin (52.6°S–197.9°E) represent clear examples of tectonic inversion. The reactivation structures [3] are the result of previous impact-related normal faults that were reactivated due to the compressive tectonic regime deriving from the global contraction. Similarly to the Victoria quadrangle (H-02) [4], in the Michelangelo quadrangle the NW-SE system borders the southwestern edge of the high-Mg region, although the accuracy of XRS data at these latitudes is much lower than the accuracy of data acquired in the Northern hemisphere. We noted the frequent interaction between volcanic vents and thrusts, as already suggested by [5]. These vents are often located along lobate scarps or in soft-linkage zones between thrust segments. Indeed, as also observed on Earth, curved thrust surfaces or linkage areas between fault segments represent weakness zones acting as preferential pathways for magma uprising.

 

Acknowledgements: We gratefully acknowledge funding from the Italian Space Agency (ASI) under ASI-INAF agreement 2017-47-H.0.

 

References:

[1] Spudis P. D. and Prosser J. G., (1984). U.S. Geological Survey, IMAP 1659.

[2] Galluzzi et al. (2021). LPI Contrib., 2610.

[3] Fegan E. R. et al., (2017). Icarus, 288, 226-234.

[4] Galluzzi et al. (2019). Journal of Geophysical Research Planets, 124, 2543-2562.

[5] Thomas R. J. et al., (2014). Journal of Geophysical Research Planets, 119, 2239-2254.