Potential sources of Ediacaran strata of Iberia: a review

Abstract

Advances in stratigraphy, geochemistry and U-Pb detrital zircon geochronology from Ediacaran strata of Iberia allow for the improved characterisation of crustal growth in the North Gondwana active margin. The formation of Cadomian magmatic arcs and associated back-arc basins that took place in the North Gondwana active margin was a long-term process. Iberia has been placed in the Cadomian belt in currently accepted palaeogeography reconstructions at c. 570–560 Ma, based on the characteristics of Ediacaran strata. The Ediacaran strata of Iberia with outstanding geochemical homogeneity are distributed across three zones of Iberia: (1) Narcea Slates in the Cantabrian and West Asturian Leonese zones (maximum depositional age of c. 600 and 553 Ma); (2) Schist–Greywacke Complex (Lower Series) in the Central Iberian Zone (maximum depositional age of c. 578 to 550 Ma); and (3) Série Negra in the Ossa-Morena Zone (maximum depositional age of c. 590–545 Ma). Pre-Cryogenian detrital zircons found in the Ediacaran strata of Iberia seem to be related to distal sources distributed across three main areas of North Gondwana inland. The oldest detrital zircons probably derive from distal sources such as the West African craton, the Trans-Saharan belt and the Arabian–Nubian Shield, in view of the increase in distance from sedimentary basins. The West African craton is the most likely source for Archean and Palaeoproterozoic detrital zircons, while the Trans-Saharan belt and the Arabian–Nubian shield could provide a source for Tonian and Mesoproterozoic grains. The youngest zircon ages (c. 630–545 Ma), which make up the dominant population in the Ediacaran strata of Iberia, are probably derived from proximal sources as would be the Cadomian magmatic arc system, not excluding the contribution of the Pan-African orogen.