The Western Sardinian Margin: Structural Evidence from New Geophysical Data

Geletti, Riccardo ¹; Zgur, Fabrizio ¹; Del Ben, Anna ²; Romeo, Roberto ¹; Codiglia, Riccardo ¹; Accettella, Daniela ¹; Fais, Silvana ³; Fedi, Maurizio ⁴; Forte, Emanuele ²; Mocnik, Arianna ²; Pipan, Michele ²; Ramella, Riccardo ¹
(1)RIMA, Ist. Naz. di Ocean. e di Geof. Sper. - OGS, Trieste, Italy. (2) Geoscienze, University of Trieste, Trieste, Italy. (3) DIGITA, University of Cagliari, Cagliari, Italy. (4) Scienze della Terra, University of Napoli Federico II, Napoli, Italy.

During the period 18th September- 4th October 2010 a wide geophysical survey was conducted in the western Sardinia offshore (Sea of Sardinia, Italy) by the R/V OGS-Explora. The new geophysical dataset acquired across the Sardinian continental margin and the East Balearic Basin consists of 1430 km of multichannel seismic reflection profiles, 3100 km² of multibeam morphobathymetry, 580 km of high-resolution sub-bottom acoustic profiles and 915 km of magnetometric profiles.

All these data integrate the pre-existing seismic, magnetic and gravimetric information acquired by OGS within the MS (Mediterranean Sea) project during the 1972 and by AGIP (1968, 1975) for hydrocarbon exploration. The above-mentioned vintage seismic data have been reprocessed to improve the imaging of the profiles.

The available dataset depicts in detail the morphological setting of the western Sardinia margin. This continental margin, affected by tilted fault blocks and by local deposition of a prograding sequence, shows some shallow structures interpreted as magmatic bodies, as supported by the anomalies of the new magnetic measurements. A prominent slope represents the transition to the oceanic Balearic Basin characterized by numerous halokinetic structures originated by the salt Messinian unit. This salt tectonics produce several strong deformations within the Plio-Quaternary sequence, sometimes reaching the sea-bottom (evidence of knolls), in its turn favouring gas accumulations evidenced by bright spots, gas chimneys, pockmarks, etc.

The first aim of the project is to analyze the relation between the halokinetic processes and the different geological conditions as salt thickness, Plio-Quaternary sequence thickness, deepening, stress fields and tectonic features: all these elements determined a differential distribution of the halokinetics structures. The interpretation of the seismic profiles, integrated by the magnetometric data lead us to depict the distribution and correlation of the magmatic structures related to different tectonic phases that affected the Sardinian Block. Furthermore, we will characterize high-amplitude reflectors with specific seismic AVO and attribute analyses (cross-plot analysis, P and S wave reflection coefficient analysis) in order to emphasize and discriminate the gas presence. Finally we intend to focus our research to explore some pre-Messinian structures locally evidenced in both old and new seismic profiles.

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