EVALUATION OF DEVONIAN STAGES AND THEIR SUBDIVISION IN THE SPANISH CENTRAL PYRENEES. A GLOBAL PERSPECTIVE

All Devonian Stages, except the beginning of the Devonian, are defined by the entry of an index conodont. This subdivision is largely based on the conodont evolution that have thorough globally studied for the last 40 years. The base of the Devonian and therefore, of the first Stage, the Lochkovian, is defined with the entry of Monograptus uniformis. In the Spanish Central Pyrenees (SCP) this base has not been identified, but conodont records of Icriodus woschmidti together with lobolithes of Scyphocrinites suggest the proximity of the boundary. The Pyrenean sections yielded one of the most complete and abundant Lochkovian conodont record showing the potential of this area for further subdivision into the three substages envisaged by the International Subcommission on Devonian Stratigraphy (SDS). The base of the Pragian is defined by the entry of Gondwania irregularis (former Eognathodus sulcatus). In the SCP conodont and fish records bracket the boundary to a narrow interval. Further intended subdivision of the Pragian into two substages is also identified by the index conodont in several Pyrenean sections. The base of the Emsian is defined with the entry of Polygnathus kitabicus. Currently, the SDS has agreed to redefine this boundary. Numerous Pyrenean sections show a continuos conodont record embracing both, the new and the intended, boundaries and therefore these sections should play a relevant role in the redefinition of the base of the Emsian. The Pyrenean records are also important for the further subdivision of the Emsian into two substages: Lower and Upper Emsian. Facies constraint in the Pyrenees obscures recognition of the beginning of the Middle Devonian Series and of the Eifelian stage; however, the presence of P. costatus in the section Villech above a partially covered interval with records of upper Emsian conodonts suggest the vicinity of this boundary. The index of the Givetian, P. hemiansatus, is recorded in sequence with its ancestor in the SCP. The Pyrenean conodont record supports the proposed Givetian subdivision into three substages (Lower, Middle and Upper). The beginning of ancyrodellids above the uppermost Givetian norrisi Zone allows recognition of the base of the Upper Devonian Series and of its first stage, the Frasnian.