Lunar chronology and evolution inferred from the radiometric age data of Appollo and Luna rocks and soils

Radiometric ages have been determined over the samples of Apollo 11, 12, 14, 15, 16 and 17 and Luna 16 and 20 rocks and soils. From the agedating data of the lunar materials it is attempted to initiate a framework for lunar chronology. The basalts from mare regions have not undergone shock metamorphism and brecciation caused by the impact events. The ages of mare basalts from Apllo 11, 12, 14, 15, and 17 and Luna 16 data the period of flooding by basaltic lava on mare basins. The highland samples from Apollo 14, 15, 16, and 17 and Luna 20 abound with breccias-rock fragments and soils that have adhered because of the heat and pressure of impacts. Ejecta thrown up by the mare basin impacts formed the highlands. The highland rock samples (anorthositic gabbro composition but breccia texture) give a data for the cataclysm of mare basin excavation and highland formation. The ages for the mare volcanism are: Oceanus Procellarum 3.16-3.36 b.y.; Mare Imbrium 3.28-3.44 b.y.; Mare Fecunditatis 3.4-3.5 b.y.; Mare Tranquillitatis 3.56-3.83 b.y.; Mare Serenitatis 3.71-3.79 b.y.; pre-Mare Imbrium 3.95-4.0 b.y. For the highland formation: Cayley Plains --3.84 b.y.; Fra Mauro Hills --3.88 b.y.; Apennine Mountains --3.88 b.y.; Apollonius Mountains --3.90 b.y. Descartes Mountains --3.93 b.y.; Taurus-Littrow Highlands --3.98 b.y. For the impact mare basin formation: Orientale Basin --3.84 b.y.; Imbrium Basin --3.88 b.y.; Crisium Basin --3.90 b.y.; Nectaris Basin --3.93 b.y.; Serenitatis Basin --3.98 b.y. (JPN)