lunabasen.

1944 J. E. Spurr Geol. applied to Selenol. II. iv. 20 The differently colored formations which largely make up the marking of the lunar ‘map’ have, in the Imbrian study (volume I), been interpreted as probably corresponding to two main types of terrestrial rock: the light-gray ‘uplands’ as siliceous, the dark mare as basic or basaltic... In future descriptions the light-colored rocks may be called lunarite. The dark-gray mare..may be called imbase... In the mare formations south of the Mare Imbrium, a later, darker phase of presumably basic rock..may safely, and briefly, be called novabase (later lunar basaltic rock). And the inclusive term for both would be lunabase (lunar basaltic rock).

1966 Earth Sci. Rev. I. 231 Spurr (1944) gave the name ‘lunarite’ to the more highly reflective parts [of the moon's surface], and the name ‘lunabase’ to the darker parts. Large areas of lunarite are referred to as ‘continents’, and specific areas of lunabase are called ‘maria’.

1967 New Scientist 2 Feb. 263/2 The mountains [on the moon] end with steep terminal slopes of 20° or so, which cannot be due to erosion as a result of melting by subsequent lavas from the mare region (the dark lunabase).