Further paleomagnetic results from the Bloomsburg formation

Abstract

Paleomagnetic observations have been obtained from 161 specimens from the Bloomsburg redbeds (Upper Silurian) collected at 13 localities along the tectonic arc in the Valley and Ridge province in the Appalachians. The purpose was to determine if the curvature was original, or if it was produced by bending in plan, during, say, the Appalachian orogeny. Observations were obtained from the eastern and southern limbs and from the hinge area of the arc. Components of very high magnetic stability and substantial uniformity (mean D, I is 001°, −32°, precision k = 35, pole 32°N, 102°E) were found in 9 localities in the eastern limb and in the hinge area in Pennsylvania, indicating that the arc was original. In the southern limb, in Maryland and Virginia, however, less stable secondary components probably of Permian age appear to have replaced much of the original magnetization, so that a rigorous test was unfortunately not possible. Heating experiments showed that these secondary components could have been acquired during a period of moderate heating during burial.