EARLY DEFORMATIONS AT A SUBMARINE COMPRESSIVE FRONT - THE QUATERNARY CATANIA FOREDEEP SOUTH OF MT ETNA, SICILY, ITALY

In the Catania foredeep, south of Mt. Etna, oil drilling has revealed the existence at depth of an allochthonous complex emplaced during the middle Quaternary. At the surface, outcropping middle Quaternary marine marly clays and sands display complex deformations which are partly synsedimentary and which can be correlated with the emplacement of this allochthonous complex. Most of these deformations are thought to result from gravitational gliding of slope sediment apron. This process, probably facilitated by high pore-pressure, would be in particular the cause of a semi-penetrative shear deformation with an eastward vergence in the clays. Thus, our study rules out the classical view of a shallow pre-Etnean gulf that was steadily filled in before emerging some 400,000 to 300,000 years ago. This particular example of neotectonics shows the precocity and complexity of deformations occurring in sediments deposited along the compressive margin of a foreland basin or similarly at an accretionary prism front. © 1990.