Glauconite from the Precambrian Belt Series, Montana

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Science  26 Apr 1963:
Vol. 140, Issue 3565, pp. 390-391
DOI: 10.1126/science.140.3565.390


Glauconite from the upper part of the Missoula Group of the Belt Series, Flathead County, Montana, has been dated at 1070 million years by potassium-argon and rubidium-strontium analyses. This is the first glauconite of Precambrian age reported in North America.