Publication Date:
2019-07-13
Description:
An extension of a previous work on relative age mapping for the lunar nearside is presented. The ages were determined from Apollo (Hasselblad, metric, and panoramic) and Lunar Orbiter photographs; three major subdivisions were observed: maria and two older light plains units. The plains units center around 3.8 b.y. and 4.0 b.y., respectively. Ages of maria decrease westward. The oldest maria is 3.7 b.y.; it comprises Mare Tranquillitatis and two small areas in southeastern Mare Imbrium. Oceanus Procellarum, southwestern Mare Imbrium, northern Mare Humorum, and northwestern Mare Serenitatis contain the youngest maria; the youngest of these formed about 1.7 b.y. ago. Emplacement of all three subdivisions occurred over a 2.3 b.y. interval. The three-stage model of mare emplacement proposed by Soderblom (1970a) is confirmed. Thus the sequence is (1) high-Ti basalts in the eastern hemisphere, (2) low-Ti basalts filling circular ring-maria, and (3) high-Ti basalts in the western hemisphere.
Keywords:
LUNAR AND PLANETARY EXPLORATION
Type:
Lunar Science Conference; Mar 18, 1974 - Mar 22, 1974; Houston, TX
Format:
text
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