Gela Submarine Slide: Gigantic Basin-Wide Event in the Plio-Quaternary Foredeep of Sicily

A. Argnani, F. Trincardi

The Gela basin is a Pliocene-Quaternary foredeep basin located at the front of the Maghrebian fold-thrust belt of Sicily, filled with 2,500 m-thick shallowing-upward marine sediments. An important contribution to the basin fill comes from a huge, basin-wide submarine slide which extends for 3,500 km² and thickens as much as 450 m; the estimated sediment volume involved in the slide is close to 1,000 km³.

Our investigation used more than 3,000 km of multichannel and single-channel seismic reflection profiles. The slide depositional geometries and facies relationships have been reconstructed from seismic interpretation to provide insight into transport and emplacement mechanisms.

Apparently, the slide was not simply deposited via mass transfer from the slope into the basin. Indeed, the bulk of the slide is composed of basin sediments plastically deformed under the gravitational force driven by the correspondent slope sediments. Such a deformation occurred above an extremely effective decollement surface which controlled the slide distribution throughout the basin. More localized decollement planes are, however, present within the slide body and contributed to its complex deformation. The slide can thus be considered the result of a generalized gravitational collapse which affected the sediments lying above a peculiar decollement horizon.

A general uplift characterized the late Quaternary evolution of the area, and volcanic activity was quite widespread and documented in the historical record. A punctuated episode of energy release (volcanic related?), superimposed to the uplift trend, may have triggered the slide in conjunction with potentially easy detachment of a decollement.

AAPG Search and Discovery Article #91032©1988 Mediterranean Basins Conference and Exhibition, Nice, France, 25-28 September 1988.