Geologic map of the Grimaldi quadrangle of the Moon
The Grimaldi quadrangle lies at the southwest margin of Oceanus Procellarum about 1,000 km east of Orientale, the youngest o f the lunar multi-ringed basins. The distal ends of the ejecta blanket surrounding the Orient al e basin partly covers the western third of the quadrangle. The relatively small, two-ring Grimaldi basin is in the northwest corner of the quadrangle, and the Humorum basin l ies about 750 km to the southeast. A vestigial multi-ring basin mostly engulfed by mare appears to control the distribution of terra and mare along the southwest margin of Oceanus Procellarum ; the craters Hansteen and Billy are on a northwe s t-trending topographic high which represents part of the ring system of this basin. Terra materials of distinctive texture, apparently unrelated to multi-ring basins and probably of volcanic origin, occupy the central parts of the quadrangle.