Early Tertiary Age of Pitchstone in the Northern Black Hills, South Dakota

See allHide authors and affiliations

Science  10 Jun 1983:
Vol. 220, Issue 4602, pp. 1153-1154
DOI: 10.1126/science.220.4602.1153


A block of pitchstone in the northern Black Hills, South Dakota, is Paleocene in age, according to potassium-argon dating of biotite and fission-track dating of zircon in the sample. These data invalidate published suggestions that the age is much younger. The pitchstone is not extrusive in its present position but instead is in a volcanic pipe with other fragments that came downward from as much as 1100 meters above the modern surface.