Foredeep paleobathymetry and subsidence trends during advancing then retreating subduction: the Northern Apennine case (Oligocene-Miocene, Italy)

ABSTRACT: The Northern Apennines provide an example of long-term deep-water sedimentation in an underfilled pro-foreland basin first linked to an advancing orogenic wedge and then to a retreating subduction zone during slab rollback. New paleobathymetric and geohistory analyses of turbidite systems that accumulated in the foredeep during the Oligocene-Miocene are used to unravel the basin subsidence history during this geodynamic change, and to investigate how it interplayed with sediment supply and basin tectonics in controlling foredeep filling. The results show an estimated ~2 km decrease in paleowater depth at ca. 17 Ma. Moreover a change in basin subsidence is documented during Langhian time, with an average decompacted subsidence rate, during individual depocenter life, that increased from < 0.3 to 0.4-0.6 mm/y, together with the appearance of a syndepositional backstripped subsidence bracketed between 0.1 and 0.2 mm/y. This change prevented the basin from complete filling during late Miocene and is interpreted as the foredeep response to initial rollback of the downgoing Adriatic slab. Thus the Northern Apennine system provides an example of a pro-foreland basin that experienced both a slow and high subsidence regime as a consequence of the advancing then retreating evolution of the collisional system