Poster De Conférence Année : 2023

Gas migration in Holocene sediments in Greece identified by very-high-resolution seismic data

Résumé

Gases, and fluids in general, play a key role in tectonically active areas and sedimentary basins, thus, their characterisation and quantification are crucial. This case study is located in Central Greece, to the north of the Corinth rift, within the Sperchios – North-EviaGulf rift. This very young rift ( ˜3.6 Ma to present-day) results from the Aegean back-arc extension initiated by the African slab roll-back. Moreover, the westward propagation of the North-Anatolian Fault into the Aegean Sea could influence the recent deformation within the rift system. Numerous hydrothermal systems have been documented inland, especially three very hot springs (> 60◦C) in North Evia and three warm springs (30-40◦C) along the Sperchios Basin in continental Greece. These CO2-rich thermal springs present intense bubbling and important travertine formation. According to recent studies, the very hot springs are related to the local Plio-Pleistocene volcanic edifice belonging to the active Aegean volcanic arc. The warm springs are located along one of the major fault systems of the rift. No gas accumulation or emission have been reported offshore so far. From a recently acquired very-high-resolution seismic dataset, we examined the seismic markers of gas trapped in the recent sediments within the rift. The gas-related structures in the Sperchios – North-EviaGulf rift can be classified in three categories: (1) gas accumulations characterised by enhanced stratigraphic reflectors, acoustic turbidity and blanking, (2) gas chimneys recognized from localized enhanced reflections, acoustic blanking columns and hyperbole artefacts, and (3) gas leakage along fault planes highlighted by blanking, hyperbole artefacts and enhanced reflectors. Moreover, water column echoes suggest gas is released in the water column. Most of these gas-related features are present within the main Holocene depocentres. A high concentration of these structures appears within the Kandili sub-basin, where some published high-resolution tomographic data reveal the occurrence of a magmatic chamber at c. 8 km depth. Thus, the gas in this area could be thermogenic and related to this magmatic body. The gas leakages related to faults take place along E-W-striking faults. In the region, this direction corresponds to the youngest normal faults triggered by the N-S extension of the Aegean Domain.

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Dates et versions

hal-04524941 , version 1 (28-03-2024)

Identifiants

  • HAL Id : hal-04524941 , version 1

Citer

Fabien Caroir, Frank Chanier, Pierre Henry, Christopher Wibberley, Dimitris Sakellariou. Gas migration in Holocene sediments in Greece identified by very-high-resolution seismic data. 28e édition de la Réunion des Sciences de la Terre RST-2023, Oct 2023, Rennes, France. ⟨hal-04524941⟩
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