High-resolution Plio-Pleistocene chronostratigraphy of the Friulian-Venetian basin by seismic and well-log correlations

The Friulian-Venetian Basin (FVB) is the north-eastern portion of the wider Po Plain-Adriatic foreland, which bounds the whole Italian peninsula to the East, and is the place where most of the Italian hydrocarbon fields occur. The presentday architecture of the FVB is the result of the inherited Mesozoic sea-bottom topography which evolved during Cenozoic in the foreland basin shared by three different collisional systems: the Dinarides, the Southern Alps and the Northern Apennines. This work provides a high-resolution chronostratigraphic framework for the upper Neogene subsurface succession of the VFB since the early Zanclean regional transgressive surface to the latest Pleistocene, using a 2D reflection seismic lines grid and well log correlations (by spontaneous potential and resistivity signals) from Eni E&P dataset. The detailed sequence-stratigraphy analysis was based on the allogroups, (i.e. major stratigraphic units bounded at base and top by regional tectonically-induced unconformities, related to the Northern Apennines foredeep north-east migration), and on their lower rank units of climate and tectonic origin, recognized by Ghielmi et al. (2013). The almost absent deformation of the FVB sedimentary succession after Messinian well preserved the succession and allows handling the subsequent 3D basin scale interpretation. To get a high chronostratigraphic resolution we have performed a complete biostratigraphic revision of the ca. 1km-long continuously cored Venezia 1 well, integrated with near, correlatable onshore and offshore hydrocarbon wells to cover the entire Plio-Pleistocene sedimentary record. During Middle-Late Pleistocene, glaciations affected the whole Po Plain-Adriatic basin consequently suffered long periods of sea-level lowstand with large siliciclastic sediment supply followed by smaller transgressive events due to the shorter interglacials. This basin-wide short-term cyclicity is still not fully defined, but some geometries of the transgressive-regressive cyclothems are visible in seismic. In detail, into the Venetian shelf, cross-correlation panels show how the cycles can be correlated each other by well-log signals and linked to Global Eustatic sea-level curve. The resulting new age model, obtained merging biostratigraphy, seismics, direct (bottom cores) and indirect (well log) sedimentological data like electric logs, provides a new high-resolution subsurface chronostratigraphic frame for the Venetian-Friulian and Northern Adriatic basin, especially useful to date the uppermost part of the FVB Pleistocene clastic sediments, made by Milankovitch-type cyclothemes.