Caloris Basin
The Tolstoj Basin is centered in the Tolstoj quadrangle at –16°, 165° (Schaber and McCauley, 1980). It consists of three discontinuous rings; ejecta may be mapped as far as 350 km from the outermost ring. The density of superposed craters suggests an age older than the Caloris Basin, either late c1 or early c2. A small unnamed basin at –48°, 136° may also have formed in this time interval, but its age is uncertain due to its partial burial by ejecta from crater Delacroix (–44°, 129°).