Calcareous nannofossils from the Poggio le Guaine core (Umbria-Marche Basin, central Italy): Biostratigraphy and discussions on the bioevents of the Aptian–Albian interval

Abstract

The calcareous nannofossil biostratigraphy of the Aptian–Albian interval has been continuously applied and developed along the last decades. The shortage of complete and continuous outcropping marine sections and even marine subsurface sections is one of the challenges of the stratigraphic studies of this interval. Taxonomic ambiguities, diachronism and reworking are constantly pointed as challenging aspects for the calcareous nannofossil biostratigraphic studies of this interval. Amid this scenario, the Poggio le Guaine section of the Umbria-Marche Basin (central Italy) stands out by presenting a complete and undisturbed pelagic to hemipelagic marine sedimentary succession of the Aptian–Albian interval. The present work is aimed to provide a detailed biostratigraphic zonation based on calcareous nannofossils, to calibrate the results to other stratigraphic tools of previous published works and to discuss some important bioevents of the Aptian–Albian interval along the PLG core. The following biozones of the calcareous nannofossil reference zonation for the Aptian–Albian interval were recognized: the Chiastozygus litterarius Zone (NC6 Zone), the Rhagodiscus angustus Zone (NC7 Zone), the Prediscosphaera columnata Zone (NC8∗ and NC8 zones), the Axopodorhabdus albianus Zone (NC9 Zone) and the Eiffellithus turriseiffelii Zone (NC10 Zone). The PLG core encompasses the chronostratigraphic interval from the Barremian/Aptian through the Albian/Cenomanian boundaries. Finally, detailed discussions on some important calcareous nannofossil bioevents of this interval were performed, among them: the first occurrence (FO) of Hayesites irregularis, the FO of Hayesites albiensis, the last occurrence (LO) of Conusphaera rothii, the LO of Micrantholithus hoschulzii/Micrantholithus obtusus, the FO of Rhagodiscus achlyostaurion, the FO of Prediscosphaera columnata, the FO of Tranolithus orionatus and the LOs of Assipetra spp.