Benthic and planktonic foraminifera of the Paleogene Epiligurian Succession (Northern Apennines, Italy): a tool for paleobathymetric reconstruction

A paleobathymetric reconstruction, based on benthic and planktonic foraminiferal assemblages, has been carried out for the Epiligurian Succession of the Northern Apennines chain (Middle Eocene-Early Miocene). The paleobathymetric interpretation has been obtained from the integration and comparison of four parameters used separately by previous authors: i) Plankton/Plankton+Benthos ratio; ii) benthic morphogroups, both infaunal and epifaunal, iii) planktonic "paleobathymetric indexes"; iv) relative abundance of benthic index species belonging to depth-dependent habitats. The applied method has been carefully discussed with respect to the studied geological setting. Moreover, the possible impact of taphonomic processes, such as selective preservation, transport and redeposition, has been evaluated. It resulted absent or limited and than, no influential on the reliability of the obtained data. The main results can be summarized as follows: an overall shallowing upwards trend is observed; in particular, a lower bathyal depth (over 2000 m to about 1000 m) has been determined for the "varicoloured facies" of the Monte Piano Marls. Lower to middle bathyal depth (about 1000 m to 600 m) have been obtained for the "grey facies" of the same formation and for the sandstones of the Ranzano Fm. Finally, the Antognola Marl Fm. (and its lateral equivalent units) contains foraminiferal assemblages indicating an upper bathyal paleodepth (about 600 m to 200 m). This shallowing up trend is tentatively related to the history of vertical motion ("geohistory") of the underlying Ligurian orogenic wedge from the Middle-Late Eocene to the Early Miocene, in response to tectonics and sedimentary load.