First record of Anisian deposits in the Betic External Zone of southern Spain and its paleogeographical implications

Abstract

In the External Zones of the Betic Cordillera (S Spain), upper Muschelkalk (Ladinian) facies have been known for decades; however, so far there is no stratigraphic record of Anisian deposits. In the present study, new biostratigraphic data from a carbonate succession in the easternmost Subbetic domain reveal a Pelsonian-Illyrian (Anisian) age. The nautiloids Germanonautilus salinarius and Germanonautilus saharonicus are documented for the first time in the Iberian Peninsula, and together with the brachiopod Tetractinella trigonella and the bivalves Neoschizodus orbicularis and Myophoria vulgaris they represent marker fossils of Anisian deposits previously described from many other basins, both in the Germanic and Alpine realms. The co-occurrence of the nautiloid G. saharonicus and the bivalve Gervillia joleaudi at the top of the studied succession serves as correlation tool for the first faunal migration event from the Sephardic towards the Subbetic domain. The palynomorph assemblage, including the monosaccate pollen grain Cristianisporites triangulatus, provides further evidence of a late Anisian age. An integrated study of fossil assemblages and sedimentary facies reveals tidal and very shallow-marine environments that characterize an extensive epicontinental platform in the western Tethys along the paleo-margin of the Iberian Massif. Two thin shale intervals represent two distinct transgressive phases, correlative to the Pelsonian maximum-flooding zone recorded in other European basins. The new findings contribute to the ongoing paleogeographic reconstruction of epicontinental platform settings which developed during the Middle Triassic in the Peri-Tethyan realm.