PALEOMAGNETISM OF THE CATOCTIN VOLCANIC PROVINCE - A NEW VENDIAN-CAMBRIAN APPARENT POLAR WANDER PATH FOR NORTH-AMERICA

The Vendian/Cambrian segment of the Lauretian apparent polar wander pa th (APWP) has been poorly constrained and the subject of some controve rsy. The Catoctin volcanic province in central Virginia is well-dated at 570 +/- 35 Ma (Rb-Sr) and 597 +/- 18 Ma (U-Pb) and therefore presen ted an excellent paleomagnetic target for resolving the Laurentian Ven dian-Cambrian APWP. A total of 206 samples from 32 sites were collecte d from the Catoctin basalts, feeder dikes and sills. The study reveale d three ancient directions of magnetization. The youngest, C component , fails the fold test and yielded a characteristic in situ direction o f D=147-degrees, I=+44-degrees (k=21, alpha95=9-degrees). The correspo nding paleopole falls along the Middle Ordovician segment of the Laure ntian APWP and we consider this component to be the result of a Taconi c remagnetization. The second component, the B component, is carried b y hematite, exhibits dual-polarities and passes a fold test. The tilt- corrected B component characteristic direction is D=92-degrees , I=+17 -degrees (k=16, alpha95=13-degrees). The corresponding paleopole at 4- degrees-S, 193-degrees-E falls near a well-established Late Cambrian ( 505 Ma) pole for Laurentia, and we consider this component to be a rem agnetization during a Late Cambrian tectonic event in the central Appa lachians. The third component isolated in the Catoctin basalts, the A component, yields a tilt-corrected mean of D=68-degrees, I=+84-degrees (k=59, alpha95=9-degrees). 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-degrees-S, 128-degrees-E falls significantly away f rom previously proposed Vendian poles for Laurentia. A reevaluation of previous paleomagnetic studies from coeval rock units reveals similar ly steep directions and leads us to propose a new APWP. This new APW t rack indicates that Laurentia was located near the pole during the int erval 615-580 Ma and drifted rapidly (16 cm yr-1) toward its Late Camb rian equatorial position.