Paleomagnetism of Paleozoic strata, Brabant and Ardennes Massifs, Belgium: Implications of prefolding and postfolding Late Carboniferous secondary magnetizations for European apparent polar wander

Abstract

Paleozoic carbonate rocks of the Brabant Massif, Namur Basin, and Dinant Synclinorium, Belgium, are characterized by two secondary Late Carboniferous magnetizations of uniform reverse polarity: a postfolding low unblocking temperature (300–375°C) component (LT) and a prefolding high unblocking temperature (400–550°C) component (HT). In the Namur Basin, LT magnetizations postdate late Westphalian deformation (∼305 Ma); in the Dinant Synclinorium, HT magnetizations predate early Westphalian deformation (∼316 Ma). LT magnetizations for the combined Brabant Massif and Namur Basin sites give a south paleopole at 42.3°S, 339.6°E (dp = 1.9°, dm = 3.8°), consistent with the European cratonic reference. The LT magnetizations in the Dinant Synclinorium give a paleopole at 36.2°S 321.0°E (dp = 2.4°, dm = 4.7°). The HT magnetization gives paleopoles at 34.1°S, 333.4°E (dp = 2.6°, dm = 5.1°; Brabant and Namur) and at 25.9°S, 321.5°E (dp = 3.5°, dm = 6.8°;, Dinant Synclinorium). Declinations indicate ∼15° clockwise rotation of the Dinant Synclinorium with respect to the Brabant Massif after acquisition of the LT magnetization. Devonian red beds yield near univectorial apparent synfolding magnetizations of distributed unblocking temperature that we interpret as artifacts of the remanence acquisition or deformation processes. The HT paleopole for the Brabant Massif is indistinguishable from other early Late Carboniferous European paleopoles and is similar to poles interpreted to be derived from remagnetizations in the British Isles. Age constraints on the time of remanence acquisition of secondary magetizations allow a refined calibration of the European apparent polar wander path. Inclinations of the LT and HT components indicate about 6–8° (∼700 km) northward motion during the Late Carboniferous.