The history of lunar bombardment inferred from 40Ar-39Ar dating of highland rocks.
Abstract
Ar-40-Ar-39 age determinations for some Apollo 16 and 17 highland rocks are reported, and the chronology of lunar highland samples is discussed. While basalt 75035 is found to have an age of 3.77 b.y., the argon release patterns from two plagioclase separates of 75035 both show high-temperature increases in apparent age to 3.85 b.y., for unknown reasons. Two models of the chronology are examined. One model assumes that the ages are dominated by basin-forming events; the alternative model, in which the chronology is dominated by cratering events of subbasin size, may be used to determine cratering as a function of time close to 4.0 b.y. The association of the ages of the Apollo 17 massif rocks with the Serenitatis event restricts the basin chronology within very narrow limits, regardless of model.
- Publication:
-
Lunar and Planetary Science Conference Proceedings
- Pub Date:
- 1975
- Bibcode:
- 1975LPSC....6.1509T
- Keywords:
-
- Argon Isotopes;
- Geochronology;
- Impact;
- Lunar Rocks;
- Radioactive Age Determination;
- Apollo 17 Flight;
- Basalt;
- Breccia;
- Cratering;
- Highlands;
- Lunar Geology;
- Metamorphism (Geology);
- Petrology;
- Lunar and Planetary Exploration