Mesozoic palaeogeographic evolution of the External Zones of the Betic Cordillera

Abstract

The main events characterizing the Mesozoic palacogcographic evolution of the External Zones of the Betic Cordillera are outlined.The Triassic sediments show a 'germanic' type lacies over the entire region, ending with Late Triassic evuporites and variegated clays of Keeper facies.At the hcginning of the Jurassic a transgression takes place, and a broad shallow-marine carhonatc-platform environment appears.During the Carixian (180 Ma) the carbonate platform breaks down leading to the differentiation of two large palaeogcographic units: the Prebetic Zone where shallow-water environments prevailed throughout the Mesozoic, and the Subbctic Zone where the sediments arc clearly pelagic.Within the Prebetic Zone, two palaeogcographic realms are differentiated: the External Prebetic ,showing important stratigraphic gaps in t he .Jurassic and Early Cretaceous sequence, and the Internal Prebetic with a thicker and more continuous stratigraphic sequence.Between the Prebetic and Subbctic Zones, a palaeogeographic realm is distinguished (Intermediate units) where turhiditic and pelagic materials were deposited.This zone corresponds approximately to a slope environment during most of Mesozoic times.In the Subbctic Zone a marked differential subsidence occurs during the Jurassic, leading to trough (Median Subhetic) and swells (External and Internal Subbctic).In the Median Subbctic.the deposits consist mainly of marls, pelagic limestones, radiolarites and calcareous turbidites.with htafic volcanic and subvolcanic rocks.During the Cretaceous pelagic marls and marty limestones were laid down.Mesozoic sedimentation took place :`long the southern margin of the European plate, in an Atlantic-type continental margin underlain by continental crust.Three-dimensional schemes.explaining the main palaeogcographic events are included.