Paleomagnetism of devonian units from Miguasha, Gaspe, P.Q., Canada.

Abstract

The area investigated is located at longitude 66°30′W and latitude 48°N, on the northern shore of Chaleur Bay. Some 124 specimens (46 samples) were collected from 9 sites in the following geological formations: La Garde (10 samples, late Early to early Middle Devonian), Pirate Cove (11 samples, early Middle Devonian), Fleurant (15 samples, early Late Devonian) and Escuminac (10 samples, early Late Devonian). These formations are composed of conglomerates, silty and calcareous sandstones deposited in a continental environment. The Upper Devonian geological units are amongst a few found in Canada to the east of Alberta. The main goal of this study is a better definition of the Apparent Polar Wander Path of the Appalachians of North America. This study allowed the identification of geological formations favourable to paleomagnetic sampling. Remanent magnetizations and magnetic susceptibilities were measured; both alternating field and thermal demagnetizations were carried out. After demagnetization, 4 components (A, B, C and D) were isolated and several components were found in each formation. Fold and conglomerate tests were performed; the first is significantly negative except for component B and the second is positive in the Fleurant Formation. The mean direction of the components is: 156°, +31° for A, 52°, -46° for B, 167°, -21° for C and 223°, +25° for D. The corresponding paleopoles are 22°N 141°E, 6°S 77°E, 51°N 137°E and 17°N 83°E. Based on the fold test, degree of alteration and unblocking temperatures, it was found that components A, C and D are secondary. Component B is either primary or secondary. The relative age of acquisition of magnetization is the following: B>D>A>C. The paleolatitudes vary from 17°S to 10°N going from A to B (tilt corrected), to D and to C. The results are discussed in relation to the Devonian Apparent Polar Wander Path of North America.