Evidence for Late Tertiary Volcanic Activity in the Northern Black Hills, South Dakota

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Science  27 May 1977:
Vol. 196, Issue 4293, pp. 977
DOI: 10.1126/science.196.4293.977


Rhyolitic volcanic rock in the northern Black Hills has a potassium-argon isotopic age of 10.5 ± 1.5 million years. This is considerably younger than any previously reported igneous activity in this or adjacent areas and indicates that the renewed uplift of the Black Hills, which occurred after the Oligocene epoch, was also accompanied by some volcanism.