An expanded Cretaceous-Tertiary transition in a pelagic setting of the southern Alps (central-western Tethys).

• Published in: Palaeogeography, Palaeoclimatology, Palaeoecology
• Main Authors: FORNACIARI E., GIUSBERTI L., TATEO F., AGNINI C., BACKMAN J., ODDONE M., RIO D., LUCIANI, Valeria
• Other Authors: Fornaciari, E., Giusberti, L., Luciani, Valeria, Tateo, F., Agnini, C., Backman, J., Oddone, M., Rio, D.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2007
• Subjects: K/T boundary mass extinction; Belluno Basin; Southern Alp; Calcareous nannofossil; Planktonic foraminifera; Geochemistry; Mineralogy; Rossa
• Online Access: http://hdl.handle.net/11392/461957; https://doi.org/10.1016/j.palaeo.2007.02.044; http://usr_valut

An integrated micropalaeontological (planktonic foraminifera and calcareous nannofossils), mineralogical and stable isotope investigation was carried out across the Cretaceous/Tertiary (K/T) boundary in a previously undescribed hemipelagic section (Forada section) cropping out in the Piave River Valley (Southern Alps, Belluno Province, NE Italy). Our results suggest that an apparently complete K/T transition with an expanded basal Danian is preserved in the Forada section. The K/T boundary is marked by a ca. 1.5- cm-thick clay interval intercalated in the pelagic carbonates of the Scaglia Rossa Formation. The boundary clay, characterised by an iridium anomaly, is constituted by a basal 1–2 mm-thick “green layer” and an overlying “red layer”. Below the boundary clay, the calcareous nannofossil Micula murus Zone and the planktonic foraminiferal Plummerita hankteninoides Zone, that characterise the terminal Maastrichtian in complete sections, have been identified. Virtually all the calcareous plankton biohorizons normally utilised in the early Danian have been recognised. Interestingly, the ranking of the various biohorizons is the same observed elsewhere if considering the single plankton groups separately, while several inconsistencies emerge if considering the relative succession of the two calcareous plankton groups simultaneously.We caution to infer hiatuses on a section based only on the spacing of the biohorizons of a single group because of the risk of diachroneities in the stressed early Danian environment. By comparing the “distance” of the key biohorizons (i.e. the First Occurrence (FO) of Cruciplacolithus primus and the Last Occurrence (LO) of Parvularugoglobigerina eugubina) from the boundary clay at Forada and in other complete classical sections, we have inferred that the early Danian is expanded in the Forada section. The section seems ideally suited for studying the recovery pattern of the pelagic ecosystem and calcareous plankton communities in the aftermath of the K/T catastrophe in a pelagic ...