K analyzed by G. Edsall, Kristina Ahlnas, and Diane Duvall with a digital flame photometer (Instrumentataion Laboratories, model 343) using the LiBO2 flux fusion technique and mineral calibration standards. Ar analyzed and ages calculated by Donald Turner, Wilfred Davis and Diane Duval using isotopic dilution, using 38Ar tracers, and a mass spectrometer (152.4-cm radius) (Nuclide Corporation) equipped with automated peak stepping and a digital data-acquisition system.