SHRIMP U–Pb geochronological constraints on the timing of the intra-Alcudian (Cadomian) angular unconformity in the Central Iberian Zone (Iberian Massif, Spain)

Abstract

source areas verifies recent studies that point to the Cadomian foreland in the north Gondwana continent affected by the Pan-African orogeny: the West African Craton and/or the Saharan Metacraton. Furthermore, ongoing Cadomian arc-related magmatism in Iberia (c. 605-545 Ma) could have contributed as a local zircon source. The end of the Cadomian activity is marked by a transient stage (ephemeral Lower Cambrian platform) which preceded widespread Cambro-Ordovician rifting of north Gondwana.

Pistas fósiles y dubiofósiles del Ediacárico y Cámbrico del Anticlinal de Alcudia, España

“…If they were trace fossils of bilateral organisms, they would imply that at least some parts of the Lower Alcudian are younger than about 555 Ma, since this is the age of the oldest unambiguous bilateral traces (Jensen, 2003;Fedonkin et al, 2007). This age would be in agreement with the radiometric dating of this subunit (< 580-560 Ma according to Talavera et al, 2015).…”

“…5B) was found in the sole of a coarse-grained turbidite immediately below the intra-Alcudian unconformity of El Chorrillo (Solanilla del Tamaral, Fig. 1) described by Palero (1993) and dated by Talavera et al (2015), who found it to be younger than 580±7 Ma using detrital zircon radiometric geochronology. The disc is very similar to the holdfast of an Ediacaran frond such as Charniodiscus, but ultimate proofs of biogeneicity are lacking.…”

“…The axis of the valle de Alcudia is the Lower Alcudian subunit, a thick (4,000-6,000 m), generally subvertical, usually flysch-like alternation of greywackes and siltstones representing turbidites and gravitational breccias of probable late Ediacaran age, being younger than about 580-560 million years (Ma) according to radiometric geochronology using detrital zircons (Talavera et al, 2015). This subunit is considered to have been deposited on a continental slope (Pieren Pidal, 2000;.…”

“…Its rocks are weakly metamorphosed, corresponding to the low and occasionally high anchizone (Pieren Pidal, 2000;. This subunit is overlain by the Upper Alcudian, in angular unconformity (< 550-540 Ma according to Talavera et al, 2015).…”

Detrital zircons from the Ordovician rocks of the Pyrenees: Geochronological constraints and provenance

“…After the early works by Fernández-Suárez et al (2000) and Linnemann et al (2000), the age signatures of detrital zircons have been widely used in the European Variscan belt and in the basement rocks involved in the Mediterranean Alpine orogenic belt to determine the potential provenance areas for the metasediments and thus to assess Ediacaran-early Paleozoic paleogeographic models (see discussion in Avigad et al, 2012;Meinhold et al 2013). Zircon age spectra have also been used to determine the maximum depositional age of the thick unfossiliferous lowermost preVariscan series (Díez-Fernández et al, 2012;Talavera et al, 2012) and to determine the time gap involved in certain unconformities in the Iberian Massif (Talavera et al, 2015).…”