Examination of a number of ancient turbidite basins in the Alpine geosynclinal chains of the circum- Mediterranean region supports the assumption that many of the sediments therein were deposited in deep-sea fan environments. Sand—body geometry and vertical sequence analysis provide criteria for detecting associations of inner, middle, and outer fan facies in these turbidite sequences.
Examples of these three main facies associations are reported from selected Tertiary geosynclinal tur- bidites occurring in the northern Apennines (Ranzano Sandstone and Bobbio Formation) and on the island of Rhodes, Aegean Sea (Messanagros Sandstone). The proposed depositional model based on these studies is not unlike models of certain deltaic systems and emphasizes progradational, aggradational, and recessional events of turbidite sedimentation in complexes of ancient deep-sea fans.
Middle fan deposits commonly show thinning and (or) fining upward cycles developed within channel-fill sequences. Such cycles are readily comparable to those of abandoned fluvial channels that are also filled with similar sequences in delta-plain environments. In both cases, channel and interchannel areas indicate prevalent vertical accretion. Active deltaic outbuilding is expressed typically by stream-mouth bars whose progradational character is shown by the occurrence of thickening and (or) coarsening upward cycles. Detailed inspection of several northern Apennine turbidite formations has shown that sandstone bodies, closely exhibiting such a progradational pattern, are extremely widespread. These turbidite sediments are here interpreted as outer fan deposits, and are thought to be responsible for deep-sea fan growth in most ancient basins.