Formation of cryptomare in the Balmer-Kapteyn region: (a) formation of the Balmer Basin, ~4.2 Ga. (b) Ejecta coverage of large basins in the Nectarian and Pre-Nectarian after the formation of the Balmer Basin until the mare basalt filled. (c) Underplating or eruption of the mare basalt, where the mare basalt was exposed on the lunar surface and may have mixed with early basin ejecta, with the activity time between ~3.89 and 3.84 Ga. (d) Coverage of ejecta material, the mare basalt was covered with high-albedo ejecta materials. (e) Exposed mare basalt. The crater excavated the buried mare basalt, which formed the present stage of the cryptomare. The processes in(d) and (e) are interlaced and have a broad time span. For example, the ejecta of Crater Angraus were formed in the Imbrian while Crater Langrenus was formed in the Copernican.