This is a preview. Log in through your library . Abstract Isotopic age determinations (U-Th-Pb) on zircons from pegmatite and granophyre dikes in the western San Gabriel Mountains have yielded ...

The Journal of Geology, Vol. 72, No. 4 (Jul., 1964), pp. 381-399 (19 pages) Age determinations using the $Ar^{40}-K^{40}$ and $Sr^{87}-Rb^{87}$ methods were made on ...

JACKSON, Wyo. (KIFI) - The Wyoming State Geological Survey (WSGS) published a new map depicting the structural configuration of the Precambrian basement in Wyoming. "Basement" refers to very old ...