Pre-folding magnetization reconfirmed for the Late Ordovician-Early Silurian Dunn Point volcanics, Nova Scotia

Abstract

Paleomagnetic results have been obtained for three new sites in steeply inclined subareal volcanic flows of the Dunn Point Formation from the Avalon terrane of Nova Scotia. Demagnetization analysis reveals a characteristic magnetization, carried by hematite, which is similar to that reported in previous studies of this unit. A new and improved fold test for the characteristic component, combining paleomagnetic and structural data from the present study with paleomagnetic data for vertically dipping flows (and laterites) studied previously by the authors, is significantly positive. The new fold test reconfirms the prefolding age of the characteristic component. A primary age of magnetization is inferred, based on field evidence for early oxidation of the flows. The overall mean direction for the characteristic component of D = 344°, I = −60°, k = 68.6, α 95 = 4.1° (paleopole at 2°N, 130°E) corresponds to a Late Ordovician-earliest Silurian paleolatitude for Avalon of 41° S. The latter is much higher than that predicted for the area on the basis of the cratonic North America apparent polar wander path, implying a substantial post-Ordovician displacement (⩾ 1700 km) of Avalon with respect to the craton. The Dunn Point result supports previous paleogeographic reconstructions that show Avalon together with the continental blocks of Hercynian Europe and northwestern Gondwana.