Oroclines of the Iberian Variscan beltpaleocurrent analysis, U-Pb detrital zircon age dating, and paleogeographic implications

Abstract

Paleocurrent and U-Pb detrital zircon age data from the Lower Ordovician Armorican Quartzite of the Cantabrian, West Asturian-Leonese and Central Iberian zones define the geometry and paleogeography of the Iberian Variscan belt. Paleoflow directions oriented at high angles to structural strike reveal the Cantabrian Orocline of northwest Iberia to be continuous with a second, the Central Iberian Orocline. The two oroclines form an s-shaped fold pair of continental scale. Palinspastic restoration to a paleomagnetically constrained Late Variscan (Carboniferous) N-S trend yields a linear orogenic ribbon (The Cantabrian – Central Iberian Ribbon) >1500 km long characterized by passive margin strata (presumably Gondwanan) that display an offshore paleoflow towards a westerly oceanic domain (presumably the Rheic). Detrital zircons suggests that the Cantabrian-Central Iberian ribbon formed part of the L. Paleozoic Gondwanan margin that stretched east-west along the northern limits of the Saharan Metacraton and Arabian-Nubian Shield. A 90° counterclockwise rotation is required to reorient the ribbon to an Early Variscan N-S trend, suggesting post-Lower Ordovician, pre-Variscan separation from Gondwana.