Factors controlling foredeep turbidite deposition: the case of Northern Apennines (Oligocene-Miocene, Italy)

Abstract: Three major controlling factors affect turbidite deposition in foredeep basins: tectonics in the source area, tectonics in the belt-basin system, and variations of sea-level (local or global). These factors are expected to have different effects on the volume, grain size, provenance and distribution of clastic sediments during the evolution of the basin. The interplay of these factors is investigated for the latest Oligocene-Middle Miocene Northern Apennines Foredeep turbidite wedges by means of turbidite-system-based lithostratigraphy and field mapping, integrated with nannoplankton biostratigraphy and sedimentary petrogra-phy. Almost all recognized turbidite systems, unless tectonically truncated, show an overall stacking pattern formed by a lower sand-rich, t ickly bedded stage (depocentre stage) passing upward into mud-rich, thinly bedded stages, ventually grading up to mostly mudstone units (abandonment stage). This rhythmically repeated pattern is interpreted as the result of the abrupt switching on and off of coarse-grained input, coupled with an alternating increase/ decrease of depositional rate recorded in all detected systems. Biostratigraphy makes it possible to distinguish the switching-off of turbidite systems due to depocentre migration (a new system is switched on basinward) from that due to a regional decrease of clastic input