Part of the Mercurial Geologic Timescale
Calorian Period - Mansurian Period - Kuiperian Period
The Mansurian Period is the fourth period of the Mercurial Geologic Timescale. This period saw the end of planetary contraction, which had already taken its toll by the Calorian Period. A cooling in temperatures around the planet led to a thickening of the Mercurial lithosphere. The Mansurian was a time of decreased geologic activity, eventually leading to the "dead" planet that exists today, as crater formation lessened significantly during the period. The primary geologic events that mark this relatively inactive period are the formation of rayless craters, which would give way to rayed craters by the Kuiperian Period.
The Mansurian is not further subdivided into epochs.
Mansurian Timescale:
Mansurian Period - 3000-1000 MYA