Correlation between the base if drumain stage and the base of middle caesaraugustan stage in the lberian chains (NE Spain)

Abstract

Inter-regional Cambrian correlations are difficult amongst different palaeogeographic provinces, because of a lack of shared genera and species between different palaeogeographic provinces. The Drumian Stage shows this difficulty because it was defined by the FAD of the agnostoid Ptychagnostus atavus, which species has not yet been found in the Mediterranean subprovince. Thus it is necessary to establish a correlation between the ISCS scale and the local scale using other trilobites. New data from the Iberian Chains and a review of previous works suggest that the bases of Pardailhania hispida and Ptychagnostus atavus zones are approximately equivalent. Therefore Pardailhania hispida FAD could be used to mark the beginning of the Drumian Stage in the Mediterranean region. This level is easily identifiable in several places: Montagne Noire (France), Cantabrian Mountains, Demanda Mountains and Iberian Chains (Spain), Sardinia (Italy), Amanos and Sultan Mountains (Turkey), and, probably, Antiatlas (Morocco).