Abstract

The nomenclature of the thick basaltic lavas at the top of the Unkar division of the Grand Canyon upper Precambrian is discussed. It is recommended that Keyes' (1938) name of Cardenas Lavas be retained for these flows in preference to Maxson's term of Rama Formation. A new K-Ar date of at least 845 ± 15 m.y. has been determined for these lavas.

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