Scaliger Crater Region on the Moon: Evidence for Prolonged Volcanic Activity in the Australe North Basin

Australe North (35.5°S, 96°E), first identified using GRAIL, is a ~880 km pre-Nectarian impact basin [1], lying to the north of the Mare Australe (38.9°S, 93°E). The basin does not show any visible topographical signatures and its boundary does not coincide with the earlier proposed boundary of the Australe Basin defined on the basis of near circular arrangement of basalt ponds [2]. Thus, the extent of the basin and its relationship with the volcanism in the region is not well understood. The Scaliger Crater (27.1°S, 108.9°E), is a ~87 km diameter complex crater on the north-eastern flank of the Australe North Basin. The crater lies at the intersection of the outer rims of the Australe North and the pre-Nectarian Milne Basin. The effective profiling by these large-scale impacts makes it a unique site for understanding the geological evolution of the region. In this study, high resolution remote-sensing datasets have been used to decipher the geological evolution of the Scaliger Crater Region, which comprises of the Scaliger Crater and surrounding areas up till ~6 crater radii. The topographical and geomorphological evidences such as, the presence of near-concentric linear rille, lower than expected basal area of the Scaliger Crater central peak, and presence of other volcanism associated features reveal that the ring of the Australe North Basin indeed passes through the region, supporting the evidences from GRAIL. The mafic nature of the Scaliger Crater central peak and the presence of Mg-Olivine indicates the possible existence of a mafic pluton and/or lower crustal/mantle rocks in the sub-surface prior to 3.8 Ga. The basaltic units in the region i.e. mare and cryptomare also show a diversity in composition and prolonged volcanism has been observed in the region. CSFD reveal an age of ~1.7 Ga for the youngest basalts in the region. The study suggests the possibility of prolonged magmatism even in one of the oldest basins on the Moon.

Citations: [1] Neumann et al. 2015 [2] Whitford-Stark 1979