CONTROL OF REGIONAL GEOLOGY ON THE STYLE OF BASIN-PLAIN DEPOSITIONAL SYSTEMS IN THE TYRRHENIAN SEA

The 3500-m-deep Vavilov basin plain lies in the center of the Tyrrhenian Sea, and is subdivided by intrabasinal highs into the Magnaghi, the western Gortani, the eastern Gortani Basins, and the Marsili basin plain. Geophysical data allow the recent depositional character of the basins to be interpreted. The Sardinia Valley crosses the Sardinian passive margin, where intraslope fans act as sediment storage areas, and is the source of a low supply of mainly fine-grained sediments to the Magnaghi Basin. Here, a low-relief channel feeds a single, terminal lobate area that rapidly passes to basinwide sheetlike deposits. The Ischia Valley enters the eastern Gortani basin, and is mainly supplied through instability processes affecting the slope of the Latium-Campanian margin, where sediment is trapped in largely underfilled intraslope basins and subsiding coastal basins. Due to the intermittent nature of the feeding system, small, short-lived channels develop in the eastern Gortani basin plain and are rapidly replaced basinward by sheet turbidites and thick acoustically transparent layers deposited by large-volume slope-failure-induced flows that spread also over the western Gortani basin. The Marsili Basin is flanked by the tectonically active and uplifting Calabrian and Sicilian margins and is fed by the Stromboli Valley, which receives coarse-grained sediments from the presently active Aeolian volcanic arc. As a consequence, a coarse-grained fan with proximal distributary channels, small channel mouth lobes, intrachannel and interchannel longitudinal bars, and a distal, large unchannelized lobate area forms in the Marsili Basin. The present study highlights that, even in areas characterized by wide, topographically complex slopes, the regional geology of the hinterland areas is a primary external control on the style of basin-plain deposition.