An Integrated Geologic Map of the Rembrandt Basin, on Mercury, as a Starting Point for Stratigraphic Analysis

Abstract

Planetary geologic maps are usually carried out following a morpho-stratigraphic approach where morphology is the dominant character guiding the remote sensing image interpretation. On the other hand, on Earth a more comprehensive stratigraphic approach is preferred, using lithology, overlapping relationship, genetic source, and ages as the main discriminants among the different geologic units. In this work we produced two different geologic maps of the Rembrandt basin of Mercury, following the morpho-stratigraphic methods and symbology adopted by many authors while mapping quadrangles on Mercury, and an integrated geo-stratigraphic approach, where geologic units were distinguished also on the basis of their false colors (derived by multispectral image data of the NASA MESSENGER mission), subsurface stratigraphic position (inferred by crater excavation) and model ages. We distinguished two different resurfacing events within the Rembrandt basin, after the impact event, and four other smooth plains units outside the basin itself. This provided the basis to estimate thicknesses, volumes, and ages of the smooth plains inside the basin. Results from thickness estimates obtained using different methodologies confirm the presence of two distinct volcanic events inside the Rembrandt basin, with a total thickness ranging between 1–1.5 km. Furthermore, model ages suggest that the volcanic infilling of the Rembrandt basin is among the ones that extended well into the mid-Calorian period, when Mercury’s effusive volcanism was previously thought to be largely over.