Caracterización bioestratigráfica del lím ite Hauteriviense-Barremiense en las Cordilleras Béticas.

Resumen

This paper presents a detailed analysis of the stratigraphic distribution of ammonites, calcareous nannofossils and planktonic foraminifera throughout the uppermost Hauterivian-lowermost Barremian interval from several sections in the External Zones of the Betic Cordillera (southern Spain). The sequence of events recorded enables a more precise characterization of the HauterivianBarremian boundary, which is defined by the first occurrence of the ammonite Taveraidiscus hugii. A subzonal division of the ammonite standard zones can be established. So, we have divided the Balearis Zone into four subzones (Balearis, Binelli, Krenkeli and Crioceratites n. sp.), the M ortilleti Zone (= Angulicostata auct. Zone) into three subzones (Ohmi, Mortilleti and Morloti), and the Hugii Zone into two subzones (Hugii and Colombiana). Concerning the calcareous nannofossils, the most significant event is the appearance of Nannoconus circularis in the upper part of the M ortilleti Zone, linked to a sudden increase in the relative abundance of wide canal nannoconids. Planktonic foraminifera do not show, in contrast, any characteristic event throughout the studied interval.