Abstract

Lower Cretaceous mainly white and/or gray pelagic cherty limestones have been sampled in the APTICORE drill core and in the adjacent outcrop at Cismon, Southern Alps, Italy. Magnetic polarity stratigraphy of the drill core indicates that the top of the section is in the Cretaceous long normal polarity interval, 26 m above the reverse polarity zone correlative to polarity chron CM0. The base of the drilled section, at a stratigraphic depth of 116.71 m, is in a reverse polarity zone correlative to CM9. The coeval stratigraphic interval has been sampled in the adjacent outcrop in order to tie the drill core record to the outcrop. The correlation of polarity zones to polarity chrons is aided by the known correlation of nannofossil events to polarity chrons in other Italian land sections. New magnetostratigraphic sampling of the proposed Barremian-Aptian boundary stratotype section at Gorgo a Cerbara (Umbria, Italy) improves the definition of CM0 in this section and facilitates correlation to Cismon. Revised nannofossil biostratigraphy based on quantitative analyses greatly increases the stratigraphic resolution of the Barremian-Aptian boundary interval both at the proposed boundary stratotype (Gorgo a Cerbara) and at Cismon.

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