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A GIS catalogue of gas seeps around the Iberian Margin has been performed for the first time in the framework of the EMODNET-Geology-3 European project. Gas seep-related features include mud volcanoes and pockmarks but also other indicators of seabed fluid venting as the occurrence of methane-derived authigenic carbonates (MDACs) and chemosynthetic fauna hot-spots. The knowledge of these features and their distribution is relevant as they hold specific habitats, they are indicators of the presence of hydrocarbons at depth, they contain fluids rich in methane with a strong greenhouse effect, and they can induce changes in the physic-chemical properties of the sediments, causing instabilities. There are up to now 84 mud volcanoes in the southern Atlantic and Mediterranean margin, clustered into five main fields: 1) The Moroccan field (MF) offshore the Moroccan Atlantic margin; 2) the Guadalquivir Diapiric Ridge (GDR) field located on the southern Atlantic Iberian margin; 3) the TASYO field in the central GoC west off Gibraltar Strait; 4) the Deep Portuguese Margin field (DPMF) in the lower continental slope of the GoC: and (5) the West Alborán Basin (WAB) field (WAB) in the Mediterranean Sea. Gas hydrates have been collected in some mud volcanoes of GoC. In addition, extensive fields of MDAC chimneys and pavements have been identified as product of the anaerobic oxidation of methane (AOM) across the hydrocarbon seepages areas and chemosynthetic hot-spots as beds of Bathymodiulus Mauritanicus at the top of mud volcanoes. Finally, numerous pockmark fields have been detected on multibeam bathymetry and high-resolution seismic profiles across the Iberian continental margin. 198 pockmarks were identified in the Gulf of Cádiz (Atlantic Ocean) and 238 in the western Alborán Basin (Mediterranean Sea). Pockmarks, giant craters and oval depressions have also been identified in the northwestern Atlantic margin (Galicia and Cantabrian margin) and in the Murcia and Balearic Islands in the Western Mediterranean margin.
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14thInternationalConferenceonGasinMarineSediments(GIMS14),Haifa,Israel,2018
CATALOGUE OF GAS SEEPS AROUND THE IBERIAN CONTINENTAL
MARGIN: ATLANTIC VS. MEDITERRANEAN
Somoza, L.1, Medialdea, T.1, Terrinha, P.2, Pinheiro, L.3, Magalhaes, V.2, González, F.J.1, León, R.1,
Batista, L.2, Lobato, A.1
1 Marine Geology Dv, Geological Survey of Spain (IGME), Ríos Rosas 23, 28003-Madrid, Spain
2 Instituto Português do Mar e da Atmosfera (IPMA). Avda. Brasilia 6, 1449-006 Lisboa, Portugal
3 Centro de Estudos do Ambiente e do Mar (CESAM), Universidade de Aveiro, Campus Universitário de
Santiago, 3810-052 Aveiro, Portugal
l.somoza@igme.es
ABSTRACT
A GIS catalogue of gas seeps around the Iberian Margin has been performed for the first time in
the framework of the EMODNET-Geology-3 European project. Gas seep-related features include
mud volcanoes and pockmarks but also other indicators of seabed fluid venting as the occurrence
of methane-derived authigenic carbonates (MDACs) and chemosynthetic fauna hot-spots. The
knowledge of these features and their distribution is relevant as they hold specific habitats, they
are indicators of the presence of hydrocarbons at depth, they contain fluids rich in methane with a
strong greenhouse effect, and they can induce changes in the physic-chemical properties of the
sediments, causing instabilities.
There are up to now 84 mud volcanoes in the southern Atlantic and Mediterranean
margin, clustered into five main fields: 1) The Moroccan field (MF) offshore the Moroccan
Atlantic margin; 2) the Guadalquivir Diapiric Ridge (GDR) field located on the southern Atlantic
Iberian margin; 3) the TASYO field in the central GoC west off Gibraltar Strait; 4) the Deep
Portuguese Margin field (DPMF) in the lower continental slope of the GoC: and (5) the West
Alborán Basin (WAB) field (WAB) in the Mediterranean Sea. Gas hydrates have been collected
in some mud volcanoes of GoC. In addition, extensive fields of MDAC chimneys and pavements
have been identified as product of the anaerobic oxidation of methane (AOM) across the
hydrocarbon seepages areas and chemosynthetic hot-spots as beds of Bathymodiulus
Mauritanicus at the top of mud volcanoes.
Finally, numerous pockmark fields have been detected on multibeam bathymetry and
high-resolution seismic profiles across the Iberian continental margin. 198 pockmarks were
identified in the Gulf of Cádiz (Atlantic Ocean) and 238 in the western Alborán Basin
(Mediterranean Sea). Pockmarks, giant craters and oval depressions have also been identified in
the northwestern Atlantic margin (Galicia and Cantabrian margin) and in the Murcia and Balearic
Islands in the Western Mediterranean margin.
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