Geological map of Tolstoj quadrangle (H08) of Mercury

Tolstoj quadrangle is located in the equatorial area of Mercury, between 22.5°N and 22.5°S of latitude and 144° and 216°E of latitude. In this work we present the geological map (1:3M scale) performed on the quadrangle. The main basemap used for the mapping is the MDIS (Mercury Dual Imaging System) 166 m/pixel BDR (map-projected Basemap reduced Data Record) monochrome mosaic compiled using NAC (Narrow Angle Camera) and WAC (Wide Angle Camera) 750 nm-images. Moreover, to distinguish spectral characteristics and topography of the surface, MDIS global color mosaics [Denevi et al., 2016)] and the MDIS global DEM [Becker et al., 2009), have been taken into account. Then, the quadrangle has been mapped using ArcGIS at an average scale of 1:400k for a final out-put of 1:3M. The mapping highlights as Caloris basin related features dominate the geology of H08. Indeed, the southern half of the basin is located in the upper left corner of quadrangle. Inside and outside the basin extended smooth plains were emplaced and they represent the most extended volcanic deposits in the quadrangle. Also structural framework is mainly linked with the basin with radial and concentric grabens located in its floor and wrinkle ridges widespread both on the interior and exterior Caloris smooth plains. Further, lobate scarps have been detected in the quadrangle: they are located outside the Caloris basin but they are absent within its floor. These thrusts show a preferential orientation in the smooth plains located outside the basin whereas they are more randomly oriented in the intercrater plains. Besides smooth plains, products of effusive volcanism, features related to explosive volcanism have also been frequently detected. Interestingly, several volcanic vents have been identified in the inner Caloris smooth plains, aligned with the rim of Caloris basin, suggesting a correlation between these two features. However, vents are not clustered only inside Caloris basin, but other crater floors are affected by this type of features. The vents are surrounded by extended pyroclastic deposits appearing in bright yellow in MDIS enhanced global color mosaics. Finally, hollow fields have also been mapped, although they are not very frequent. Some of them are associated to the pyroclastic deposits located along Caloris rim, the others are detected within floors or peaks of a few craters in the intercrater plains.

The geological map will be integrated into the global 1:3M geological map of Mercury (Galluzzi et al., 2021), which is being prepared in support to ESA/JAXA (European Space Agency, Japan Aerospace Agency) BepiColombo mission.

 

Acknowledgements:  We gratefully acknowledge funding from the Italian Space Agency (ASI) under ASI-INAF agreement 2017-47-H.0 and from the GMAP, Europlanet RI 20-24 grant n.: 871149-GMAP

References:

Becker K. J., et al. AGU, Fall Meeting, ab-stract#P21A-1189, 2009

Denevi et al.:LPS XLVII. Abstract#1264, 2016

Galluzzi V. et al.:. Planetary Geologic Mappers 2021, LPI #2610, 2021