Neogene Evolution of the Calabrian Wedge-Top Basins (Italy): Exposed Reservoir Analogues of the Off-Shore Gas Fields

Muto, Francesco ¹; Spina, Vincenzo ¹; Tripodi, Vincenzo ¹; Critelli, Salvatore ¹
(1)Earth Sciences, University of Calabria, Arcavacata di Rende, Italy.

Since the seventies, Hydrocarbon exploration focused in the Ionian side of northern Calabria, resulting in some discoveries of gas fields of economic interest. Luna field, a Tortonian thrust-related anticline, produces from two different Miocene clastic sequences. The source rock in the area is not well defined, and the seal is given by Middle-Late Miocene deposits in different sectors of the field. Sediments, which reservoir gas off-shore, are widely exposed along the Calabrian on-shore.

Middle Miocene deposits accumulated in a common wedge-top depozone of the calabrian foreland-basin system, partitioned in three distinctive depozones. The succession includes alluvial fan, near-shore and shallow-water sediments, overlain by fine-grained turbidites and evaporites. During Late Tortonian-Early Messinian, huge volumes of Sicilide-derived rocks composed of variegated clay matrix and large blocks of limestone and sandstones have been emplaced. The latter bodies can be related with the accommodation due to out-of-sequence thrusts, or with hinterland thrust propagation of the Sicilide complex. The Miocene and post Messinian emplacement of the so-called “Cariati Nappe” (CN) in the central sector of the study area interrupts the lateral continuity and affects the sedimentary supply of a such configured foreland basin. The CN includes a Middle to Upper Miocene clastic succession unconformably covering an Oligocene to Burdigalian siliciclastic flysch. It shows two thinning and fining-upward units made of conglomerates and sandstones showing braided fluvial and deltaic facies associations, evolving to prodelta turbiditic bodies.

Structural data show that the CN is a transpressive structure formed along restraining bends of the NW-SE striking, left-lateral, Rossano-S.Nicola Fault Zone. This structure represents the distal sediments of the Miocene basin infill, together with its back-thrusted bedrock. Along the outer front of the northern Calabria, strike-slip regional fault zones, produced regional wrenching of the Miocene basins and controlled the development of intrabasinal structural highs (like the CN) related to backthrust and producing tectonic inversion in some sectors. Since the CN can be considered as exposed analogue of the off-shore structural highs, it is pointed out that at the scale of the whole basin, major compressional structures are timedependent, as they are Middle Miocene in age within the Crotone basin (see Luna Field).

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