Editing Pre-Nectarian (section)

==Description==
Pre-Nectarian rocks are rare in the lunar sample suite; they are mostly composed of lunar highlands material which have been heavily churned, brecciated, and thermally affected by subsequent impacts, particularly during the Heavy Bombardment Eon<ref>Fernandes V. A., Fritz J., Weiss B., Garrick-Bethel and Shuster D. (2013) The bombardment history of the Moon as recorded by 40Ar-39Ar chronology. Meteor. and Planet. Sci. 48, 241–269. DOI: 10.1111/maps.12054.</ref><ref>Fritz J., Bitsch B., Kührt E., Morbidelli A., Tornow C., Wünnemann K., Fernandes V.A., Grenfell L.J., Rauer H., Wagner R. and [[Stephanie C. Werner|Werner S.C.]] (2014) Earth-like habitats in planetary systems. Planetary and Space Science 98, 254–267. https://dx.doi.org/ 10.1016/j.pss.2014.03.003i</ref> (HBE; a period of 0.6-1 Gy from the formation of the Moon until at least the formation of the Imbrium Basin ~3.9 Ga, or even later with the formation of Orientale Basin) that marks the approximate beginning of the [[Nectarian]] period.  The primary pre-Nectarian lunar highland material is dominated by the rock type [[anorthosite]], which suggests that the early stage of lunar crustal formation occurred via mineral crystallization of a global [[magma]] ocean.

This geologic period has been informally subdivided into the ''Cryptic Era'' (4.533 - 4.172 Ga ago) and Basin Groups 1-9 (4.172 - 3.92 Ga ago),<ref name="W87">{{cite book | title =Geologic History of the Moon  | url =http://ser.sese.asu.edu/GHM/ | last = Don Wilhelms | publisher =  U.S. Geological Survey Professional Paper 1348 | year = 1987}}</ref> but these divisions are not used on any geologic maps. Similarly the later period has also been called the ''Aitkenian'' period.

{{Timeline_Lunar_Geological_Timescale}}