Terrane wrecks (coupled oroclines) and paleomagnetic inclination anomalies

Abstract

Three major orogenic belts that are host to coupled oroclines (terrane wrecks) are likewise characterized by or directly associated with paleomagnetic inclination anomalies: (1) the North American Cordillera, (2) the Western European Variscan belt, and (3) the Eastern European Alpine system. Implied paleolatitudinal discrepancies in each orogen are of similar magnitude to the translation required by orogen-parallel shortening during oroclinal formation. The Alaskan coupled oroclines accommodated >3000km of orogen-parallel shortening in the North American Cordillera, where primary remanent paleomagnetic inclinations in Late Cretaceous rocks require the bulk of the belt to have been translated 2000 to 3000km northward relative to cratonic North America. The Iberian coupled oroclines accommodated 1100km of orogen-parallel shortening in the Western European Variscan belt, within which mid-Paleozoic paleomagnetic inclinations are shallow with respect to stable Gondwana. The implied existence of a 3500km wide Paleotethys Ocean between the Variscan autochthon and the north Gondwana margin is seemingly at odds with paleontological constraints. The Carpathian–Balkan oroclines accommodated >1000km of orogen-parallel shortening in the Eastern Alpine system, directly north-northeast of an eastern Mediterranean region where primary remanent inclinations in Late Oligocene to Miocene rocks require northward translation between 500 and 1000km.Palinspastic restoration of the Alaskan and Carpathian–Balkan oroclines fully accounts for the translations recorded by the Cordilleran and Eastern Mediterranean inclination anomalies, respectively. Restoration of the Iberian coupled oroclines confirms the existence of Paleotethys, but only accounts for one third of the paleolatitudinal discrepancy recorded by the Variscan inclination anomaly. Fully resolving the Variscan inclination anomaly requires: (1) a paleomagnetic data set of greater temporal and spatial extent; (2) refinement of the geometric and geological continuity of the Variscan belt across Western Europe.