Le ichnocenosi delle successioni sedimentarie Eocenico-Mioceniche affioranti tra il Lago Trasimeno e l’Alpe di Poti (Appennino Settentrionale)

The ichnocoenoses of the Eocene-Miocene sedimentary successions of the Lake Trasimeno and Alpe di Poti area (Northern Apennines). This study focuses on the sedimentological, stratigraphical and ichnological integrated analysis of turbidite sequences in the Trasimeno-Alpe di Poti sector of the northern Apennines. In this area, located at the transition between the Tuscan and Umbrian Apennines, many stratigraphic units of outer Tuscan domain (Scaglia Toscana, Macigno, Arenarie di Celle and Marne di Vicchio) and inner Umbrian domain (Marnoso-Arenacea and Monte Santa Maria Tiberina) crop out. The aim of this study is to determine the ichnological content in the pelagic/hemipelagic, turbiditic, contouritic, slurried beds and other debris flow deposits which constituted, from the Eocene to the Middle Miocene, a complex suite of environments and sub-environments evolving into foredeep and wedge top basins. The ichnological content of different facies assemblages has been described from 12 stratigraphical sections. Lithostratigraphic units are Scaglia Toscana, Macigno and Monte Santa Maria Tiberina, where peculiar stratigraphic and ichnologic trends have been recognized. The ichnological analysis has been performed to determine the ichnodensity and ichnodiversity variation in the stratigraphical units and in each body where the stratinomic diversity and preservation of trace fossils was significative. Ichnocoenosis and taphonomic changes have been considered in order to explain palaeoenvironmental characteristics of different basinal sectors, mainly in the Macigno and Monte Santa Maria Tiberina formations where basin morphology and palaeoenvironmental changes underwent a very complex tectonics. The ichnologic metodology represents an innovative tool which can refine the classic field analyses (e.g. tectonics, stratigraphy, sedimentology and micropaleontology) carried out in the studied sector of the Apennines since the last century.