Geologic map of the Byrgius Quadrangle of the Moon

The Byrgius quadrangle, at the western edge of the near side, lies in the terra southwest of Oceanus Procellarum between the Humorum and Orientale basins. Structures and deposits related to the Orientale basin, which is younger than the Humorum basin (Hartmann and Kuiper, 1962), dominate the southwestern half of the quadrangle. The northeastern half is dominated by mantling deposits that are older than Orientale (Imbrian) and younger than Humorum (pre-Imbrian), which lies mostly outside the zone of recognizable Orientale-related deposits or structures. These main subdivisions are visible on the albedo map of the Moon (Pohn and Wildey, 1970), the northeastern one having generally the lower albedo. The older units throughout the quadrangle have complex topography, probably formed mostly intersecting, degraded craters.