Turbidite dispersal in a Miocene Deep-sea plain: The Marnoso-Arenacea of the Northern Apennines

Abstract

Deposition in a typical 'flysch trough' (Marnoso-arenacea or Inner Basin of 'the Periadriatic Apenninès) was interpreted in terms of the depositional system (slope-deep-sea fan-deep-sea plain)' The basin fill is wedge-shaped and shows vertical and lateral grading; in its proximal portion, it forms a progradational turbidite 'suite' with upward increase in grain size, sand content and bed thickness indicating a transition from deep-sea plain via outer-fan to inner-fan environment. The outcropping part of the plain is 175 km long. Detailed studies of lateral variations of single beds show that:(1) sandy lobes from outer fans prograded into the plain over a distance of 25-50 km; (2) 30-40% of basin plain turbidites are more than 40 cm thick, and 15 out of 100 can be correlated axially over a distance of more than 125 km; (3) these single, huge turbidites (called Contessa-like beds) were introduced from different, lateral and axial sources but their dominant dispersal was axial.