Ruolo della morfologia sottomarina nei processi sedimentari del margine tirrenico sud-orientale

Abstract

This paper reports the results of a study carried out on sediments recovered from the continental shelf and slope of the southeastern Tyrrhenian margin to define the relationship between sedimentological and morphological features. The Tyrrhenian margin has a much varied morphological setting because of recent tectonic activity. Eighty-five samples, mostly collected with a Shipek sediment sampler, were analysed using current methods (wet seiving, pipette, etc.) and then statistical assessed using cluster analysis. Six clusters have been obtained. Two clusters formed of coarse-grained deposits are present in the widest portion of the shelf internal part and are related to both fluvial supply and authigenic sediments. Another cluster falls in the narrowest part of the shelf, where the influence of rivers flow is negligible. The textural characteristics of the sediments in this cluster are typical of high energy - e.g. wave- and current-controlled - processes. These processes, which winnow the finest sediments, are particularly active in the lowest parts of the shelf and in the zone immediately above the shelf break, as shown by another cluster. Finally, two other clusters characterise the low gradient slope and the high gradient slope, respectively. The characteristics of the low gradient slope indicate slow deposition, whereas those of the second, which groups very fine-grained sediments, reflect mass transport and rapid deposition. The spatial distribution of the six clusters clearly indicates that the textural pattern of deposits is highly conditioned by the morphological setting of this part of the Tyrrhenian margin.