Recent volcanism and tectonism in the pre-Nectarian basins Grimaldi and Crüger-Sirsalis: Shreds of evidence from LRO, Chandrayaan-1, and Kaguya

Abstract

Datasets from remote sensing missions such as Kaguya, LRO, GRAIL, and Chandrayaan-1 have substantially improved our understanding of the geology of the Moon by revealing new details about impact cratering, volcanism, and tectonism. Most of the late-stage (< 2.8 Ga) volcanic activities on the Moon occurred in the Procellarum KREEP Terrain (PKT). It is understood that the heat energy required to drive these internal activities can be accounted for by the enrichment of radioactive elements in the PKT. However, some of these activities have also been reported far from the PKT, such as in the Orientale Basin, Moscoviense Basin, and SPA Basin, which indicates that the radioactive heating may not be the only driving force for their occurrences. Also, recent tectonic activities, primarily manifested in the form of fresh lobate scarps, have been revealed from several locations across the Moon with the help of LROC-NAC high-resolution images. In view of the above, to understand the driving force, it is vital to investigate the global distribution of such geologically young volcanic and tectonic formations and study their geological context in detail. Here, we have carried out a comprehensive geological investigation of the area situated near the western boundary of the PKT between the Oceanus Procellarum and the Orientale Basin. The region is comprised of two pre-Nectarian aged old degraded impact basins Grimaldi and Crüger-Sirsalis. Surface topography, geomorphology, spectral reflectance studies, and crater chronology have been carried out to decipher the geological evolution of these basins especially focusing on their volcanic and tectonic history. It has been found that both these basins experienced unexpectedly prolonged volcanism and tectonism. Whereas the volcanism continued from approximately 4.2 Ga to 1.4 Ga in the older Crüger-Sirsalis Basin, it extended from about 3.5 Ga to 700 Ma in the Grimaldi Basin. Also, shreds of evidence of Copernican aged tectonic features have been found in both these basins suggesting that the Moon is geologically active and has a much more complex geological evolution than previously understood.