Abstract

Results in the potassium-argon dating program at Berkeley are reported. Geologically well-classified authigenic sediments ranging from Miocene (12 m.y.) to Givetian (285 m.y.) have been analyzed utilizing equipment designed to date materials of low radiogenic argon content. Age determinations of seven glauconites from the Oligocene (30 m.y.), Eocone (45 m.y.), and Paleocene (55 m.y.) of New Zealand are consistent with the stratigraphy and correspond to the few previous U-Pb and K-A dates for that segment of the geological time scale. Ages of three Miocene glauconite samples from New Zealand are anomalously high compared to those of the Oligocene samples, which may be too low. The age for an Albian glauconite from Canada is too high compared to that of other samples dated. Dating of a Cenomanian feldspar and a Givetian sylvite from Canada is consistent with the Holmes B time scale. Possible explanations are offered for the discrepancies, and further experiments are suggested.

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