, Volume 13, Issue 1-3, pp 259-276

Cosmic ray exposure ages of features and events at the apollo landing sites

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Abstract

Cosmic ray exposure ages of lunar samples have been used to date surface features related to impact cratering and downslope movement of material. Only when multiple samples related to a feature have the same rare gas exposure age, or when a single sample has the same81Kr-Kr and track exposure age can a feature be considered reliably dated. Because any single lunar sample is likely to have had a complex exposure history, assignment of ages to features based upon only one determination by any method should be avoided. Based on the above criteria, there are only five well-dated lunar features: Cone Crater (Apollo 14) 26 m.y., North Ray Crater (Apollo 16) 50 m.y., South Ray Crater (Apollo 16) 2 m.y., the emplacement of the Station 6 boulders (Apollo 17) 22 m.y., and the emplacement of the Station 7 boulder (Apollo 17) 28 m.y. Other features are tentatively dated or have limits set on their ages: Bench Crater (Apollo 12) ⩽99 m.y., Baby Ray Crater (Apollo 16) ⩽2 m.y., Shorty Crater (Apollo 17) ≈ 30 m.y., Camelot Crater (Apollo 17) ⩽140 m.y., the emplacement of the Station 2 boulder 1 (Apollo 17) 45–55 m.y., and the slide which generated the light mantle (Apollo 17) ⩾50 m.y.