A negative carbon isotope excursion within the Dufrenoyia furcata Zone: proposal for a new episode for chemostratigraphic correlation in the Aptian

In this work we discuss a proposed updated division of the C7 isotope segment of MENEGATTI et al. (1998). The new standard division of the segment C7 is based on a revision of published Barre- mian-Aptian carbon isotope curves from stratigraphic sections of the Prebetic Domain in Spain. It includes four distinct isotopic subunits labeled C7a to C7d, with a characteristic negative carbon isoto- pe excursion at the base of the segment and which correlates with the Dufrenoyia furcata ammonite Zone. The negative excursion is recognized on a regional extent, and the term Intra-Furcata Negative Excursion (IFNE) is proposed to identify it. We provide possible sites correlatable with the IFNE in both the Old and New worlds, which suggest its potential use as an even global chemostratigraphic marker for the Aptian record.