The Pliocene to Pleistocene Succession of the Hyblean Foredeep (Sicily, Italy)

Ghielmi, Manlio ¹; Amore, Maria R.²; Bolla, Eleonora M.³; Carubelli, Paolo ³; Serraino, Claudio S.³; Knezaurek, Gabriella ³
(1)ESEI, Eni S.p.A. Exploration & Production Division, San Donato Milanese, Italy. (2) ENAF, Eni S.p.A. Exploration & Production Division, San Donato Milanese, Italy. (3) SPES, Eni S.p.A. Exploration & Production Division, San Donato Milanese, Italy.

Hyblean Foredeep (HF) develops in the south-eastern part of Sicily and represents the southernmost Pleistocene foredeep basin of the Apennines. This narrow and elongated depocenter is split in 3 sub-basins: Catania, Gela and Pina Basins. The HF inner and outer boundaries are represented by the Gela Nappe front and by the Hyblean foreland ramp.

By means of subsurface data 3 allogroups (Late Messinian - LM, Early Pliocene - EP, Late Pliocene - LP) and 6 sequences (4 in Pliocene: PL1-PL4; 2 in Pleistocene: PS1-PS2) were recognized in the Plio-Pleistocene HF succession. They are bounded by tectonic or eustatic-controlled boundaries, generally corresponding to abrupt changes in depositional systems type and distribution. The proposed new lithostratigraphy for HF includes some new formations: Ponte Dirillo, Irene Sand, Argo and Zagara Fms.

During the first part of Low. Pliocene, the area is interested by a foreland continental sedimentation. Thin sequences (10-20m) of transgressive marls of Trubi Fm. (PL1 Seq. - LM Allogroup) were deposited only in limited areas. A phase of strong subsidence at the EP allogroup boundary (“Intra-Zanclean Phase”) marks the passage to marine conditions. The PL2 and PL3 Sequences consist of a transgressive succession (40-170m) of Low. to Mid. Pliocene marls and clays of Trubi and Ponte Dirillo Fms. As a consequence of a new deformative event, the “Gelasian Phase”, the foreland deposits are unconformably overlain by deep-water sediments of the LP Allogroup. They are represented by Up. Pliocene-Pleistocene foreland ramp clays of the Ponte Dirillo Fm. and by Low.-Mid. Pleistocene foredeep turbidites up to 2000m thick. Turbidite deposits belong to highly-efficient turbidite systems, characterized by basin-scale tabular geometry and axial facies distribution. The Gela Basin turbiditic infill is represented by 800m thick Low.

Pleistocene sand lobe and ponded basin plain deposits of the Irene Sand Fm. (PS1 Seq.) and by the 1300m thick Mid. Pleistocene succession, mainly consisting of fine-grained basin plain and sand lobe deposits of the Argo Fm. (PS2 Seq.). In the Pina Basin the foredeep succession is represented by the Zagara Fm. turbidites. Low. Pleistocene PS1 Seq. is represented by basin plain turbidite clay and sand, while Mid. Pleistocene PS2 Seq. is made up of basin plain deposits and sand lobes.

The HF succession is closed by the emplacement of submarine slumps and by the deposition of a thick succession of the Prograding Complex.

AAPG Search and Discovery Article #90135©2011 AAPG International Conference and Exhibition, Milan, Italy, 23-26 October 2011.