Skip to Main Content
Skip Nav Destination

The aim of this work is to investigate the origin of the numerous, very thick deep-water sheet sandstones that dominate the lower portion of the Cellino Formation (central Italy), which represents the Lower Pliocene turbidite fill (about 2,500 m thick) of the outer Abruzzo sector of the Periadriatic foredeep. The Cellino Formation is mostly buried and crops out in a narrow belt a few kilometers west of the Cellino gas field. Very thick beds can be distinctly resolved in the well logs and correlated to the measured sedimentary sections on outcrop. Based on well-log correlation, tens of individual beds up to 23 m thick have been traced along the axis of the basin over a distance of at least 150 km and, perpendicularly to the basin, over a distance of 30–40 km. The absence of channelization, the infrequency of bed amalgamation, and the extreme sheet-like geometry of individual beds for long distances indicate a relatively uniform basin-plain setting with a low gradient and the ability of flows to traverse the entire basin from north to south; paleocurrent data taken from basal flute structures indicates south-directed flows, parallel to the depocenter axis of the basin.

The internal organization of the studied megabeds provides evidence for occurrence of long-lived waxing and waning flows and suggests deposition by gradual aggradation from sustained turbidity currents. Considering the anomalous thickness of the beds (up to ∼ 20 m), we could assume that current was steady at the timescale of deposition of the constituents of the single depositional intervals (e.g., massive basal division or climbing ripples) for periods of at least several hours. The following features observed in the megabeds of the Cellino Fm. have been argued to be characteristic of sustained currents: (1) turbidite beds of extraordinary volume and thickness, (2) very thick (0.5–6 m) massive basal divisions, (3) very frequent alternations of structureless and laminated intervals interpreted as subtle internal scour surfaces, (4) thick massive mudstone caps (1–10 m) that terminate the vertical organization of the sedimentary structures, (5) crudely developed normally graded grain-size profiles, (6) abundant organic matter, and (7) extensive water-escape features.

The occurrence of these large-volume turbidity currents, with volumes of the order of a few tens of cubic kilometers (10–80 km3), can be explained as the result of submarine slope failures. The frequency distribution of bed thickness in the correlated interval follows a segmented power-law size distribution, indicating that sediment deposition was dominated by a small number of large-volume events. This distribution can be linked to earthquake triggers, with comparably distributed magnitudes and consequently emplacement of megabeds can be directly related to seismic activity. The interaction of other external controls may have contributed to the origin of these large-volume turbidity currents. Periods of low sea level are traditionally held to be particularly dynamic in terms of turbidite deposition because a significant portion of continental shelves are exposed as subaerial coastal plains at such times. This allows rivers to dump their sediment loads closer to the shelf edge, and hence in potentially more unstable conditions. Sandy, basinal turbidites could originate from sediment failures during relative falling stage and lowstand stage of sea level forced by dramatic uplift of basin margins. In this stage, the tectonically active Cellino basin margins would have reached their greatest instability because their elevation was at a maximum and their distance from the shoreline at a minimum.

You do not have access to this content, please speak to your institutional administrator if you feel you should have access.
Close Modal

or Create an Account

Close Modal
Close Modal