Reconnaissance Paleomagnetic Investigation in the Spider Lake-Woburn Area

Abstract

The paleomagnetic research presented is concerned with geological formations outcropping in the Spider Lake-Woburn area in the southern Appalachians of Quebec. The age of these formations ranges from Precambrian to Late Devonian. Experiments combining AF and thermal cleaning and analytical techniques such as end-points, vector subtraction and the method of great circles indicate different components of magnetization. Fold test and baked contact test on the hornfels are also included. In some rock types, up to five components may be distinguished and isolated. AF demagnetization is particularly effective for the serpentinites, hornfels and metasediments and only thermal cleaning is effective on the other formations. Many of the components are secondary and the baked contact test is still equivocal. A tentative explanation of the time and mode of emplacement of the Precambrian granite gneiss is proposed. This study shows that at the Early Ordovician age, the paleopole position was located at 163°E, 29°N (mixed polarities) and at the Late Devonian age in the vicinity of 138°E, 37°N (mixed polarities).