EGU25-17204, updated on 15 Mar 2025
https://doi.org/10.5194/egusphere-egu25-17204
EGU General Assembly 2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
Gas-charged sediments and seabed related features in Thermaikos and Patras Gulfs, Greece: New findings and preliminary results
Nikos Giannopoulos1, George Papatheodorou1, Dimitris Christodoulou1, Maria Geraga1, Xenophon Dimas1, Aurelia Hubert-Ferrari2, and Basile Caterina2
Nikos Giannopoulos et al.
  • 1University of Patras, Department of Geology, Patras, Greece (n.giannopoulos@ac.upatras.gr)
  • 2University of Liege, Department of Geography, Liege, Belgium

Seabed fluid flows refer to the migration of gases and liquids through the seabed and seawater and is often associated with energy resources, benthic ecosystems, global climate and marine geohazards. Pockmarks are 'crater-like' depressions on the seafloor formed by fluid seepage. Two high-resolution marine remote sensing surveys (sub-bottom profiling, multi-beam bathymetry and side-scan sonar) have been conducted in the inner Thermaikos and central Patras Gulfs, each characterized by distinct geological settings. These new datasets have revealed acoustic anomalies indicative of gas-charged sediments and potential gas seepages.

The Thermaikos Gulf is in the northern part of the Aegean Sea, northeastern Greece. The Thermaikos Basin is part of the wider Axios basin, which extends from North Macedonia territory to the North Sporades Islands. It is characterized by extensive sedimentary deposits derived from major rivers, including Axios, Aliakmonas and Loudias and features moderate tectonic activity. Moreover, a gas field, the Epanomi Gas Field with gas and small quantities of light oil, have been discovered, onland, southeast of the Gulf. The Patras Gulf, a semi-closed basin situated in western Greece, lies within one of the most seismically active areas in the Mediterranean. It is controlled by extensive faults forming an asymmetric graben. An active and very well-documented pockmark field is located at the southeastern part of the Patras Gulf.

Seismic profiles acquired in the inner Thermaikos Gulf, have, for the first time, unveiled shallow zones of acoustic turbidity and enhanced reflectors in two distinct areas: near the city of Thessaloniki and in the western part of the inner gulf. Moreover, a pockmark and several intrasedimentary gas pockets were identified in the northern part and across extensive portions of the region, respectively. The dataset, obtained from the central Patras Gulf, revealed elongated seabed depressions exhibiting underlying columnar disturbances. These features were accompanied by gas flares detected in both seismic profiles and side-scan sonographs, indicative of gas emissions that appear to reach the sea-air interface. Furthermore, a new pockmark field was discovered at depths ranging from 70 to 90 meters, with no apparent association to the major faults of the Gulf. Ground-truthing surveys further documented the presence of bacterial mats and gas bubble emissions, reinforcing the evidence of active seepage activity.

Acknowledgments. The Thermaikos project is founded by the Athanasios C. Laskaridis Charitable Foundation.

How to cite: Giannopoulos, N., Papatheodorou, G., Christodoulou, D., Geraga, M., Dimas, X., Hubert-Ferrari, A., and Caterina, B.: Gas-charged sediments and seabed related features in Thermaikos and Patras Gulfs, Greece: New findings and preliminary results, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17204, https://doi.org/10.5194/egusphere-egu25-17204, 2025.