Paleomagnetism of the Catoctin volcanic province: A new Vendian‐Cambrian apparent polar wander path for North America

Abstract

The Vendian/Cambrian segment of the Lauretian apparent polar wander path (APWP) has been poorly constrained and the subject of some controversy. The Catoctin volcanic province in central Virginia is well‐dated at 570±35 Ma (Rb‐Sr) and 597±18 Ma (U‐Pb) and therefore presented an excellent paleomagnetic target for resolving the Laurentian Vendian‐Cambrian APWP. A total of 206 samples from 32 sites were collected from the Catoctin basalts, feeder dikes and sills. The study revealed three ancient directions of magnetization. The youngest, C component, fails the fold test and yielded a characteristic in situ direction of D = 147°, I = +44° (k = 21, α95 = 9°). The corresponding paleopole falls along the Middle Ordovician segment of the Laurentian APWP and we consider this component to be the result of a Taconic remagnetization. The second component, the B component, is carried by hematite, exhibits dual‐polarities and passes a fold test. The tilt‐corrected B component characteristic direction is D = 92°, I = +17° (k = 16, α95 = 13°). The corresponding paleopole at 4°S, 193°E falls near a well‐established Late Cambrian (505 Ma) pole for Laurentia, and we consider this component to be a remagnetization during a Late Cambrian tectonic event in the central Appalachians. The third component isolated in the Catoctin basalts, the A component, yields a tilt‐corrected mean of D = 68°, I = +84° (k = 59, α95 = 9°). This component passes a fold and reversal test. A suite of samples was collected from two Catoctin feeder dikes and surrounding country rocks that yield a positive baked contact test. The A pole at 43°S, 128°E falls significantly away from previously proposed Vendian poles for Laurentia. A reevaluation of previous paleomagnetic studies from coeval rock units reveals similarly steep directions and leads us to propose a new APWP. This new APW track indicates that Laurentia was located near the pole during the interval 615–580 Ma and drifted rapidly (16 cm yr−1) toward its Late Cambrian equatorial position.