caa a22 4500 463216326 CHVBK 20180405153157.0 cr unu---uuuuu 170326e20070601xx s 000 0 eng 10.1007/s00367-007-0065-3 doi (NATIONALLICENCE)springer-10.1007/s00367-007-0065-3 High-resolution mapping of shallow gas accumulations and gas seeps in San Simón Bay (Ría de Vigo, NW Spain). Some quantitative data [Elektronische Daten] [Jorge Iglesias, Soledad García-Gil] San Simón Bay in the innermost part of the Ría de Vigo is characterized by an abundance of very shallow gas accumulations and methane seeps. During the expeditions of April-June-September 2004 within the Spanish-funded Gs2G project, detailed very high-resolution seismic and field investigations were carried out to study the shallow gas and the seeps. Direct gas fluxes also were measured from bubble streams. For the first time, the surface area and gas front depth of a shallow gas field has been mapped and quantified in the inner bay of Ría de Vigo. This field overlaps spatially with the distribution of Holocene mud within the bay. Seismic data show 3.6km2 affected by acoustic turbidity but this surface can be extended up to 9.5km2 of San Simón's muddy subtidal area. Mounded turbidity superimposed on the main gas field has been mapped and characterized as anthropogenically (mussel rafts) mediated gas accumulations. Different acoustic anomalies have been identified and interpreted as being due to gas escapes from the present seabed sediment. The very high resolution of the seismic data makes it possible to identify a new type of seep, here named ‘acoustic smoke.' A direct relationship can be observed between the gas front of accumulations and escape features, both acoustic seeps and pockmarks. The methane flux has been estimated from the subtidal environment in San Simón based on detected acoustic targets and direct measurements of current bubble flow. The total estimated methane flux from the seabed into the water column ranges from 10.1 to 48.8t/year, and into the atmosphere from 7.0 to 34.2t/year. The intertidal San Simón environment is also actively venting methane, as indicated by the presence of bubbling during high tide and white patches of Beggiatoa sp. Springer-Verlag, 2007 Iglesias Jorge Departamento de Xeociencias Mariñas e Ordenación do Territorio, Universidade de Vigo, 36200, Vigo, Spain aut García-Gil Soledad Departamento de Xeociencias Mariñas e Ordenación do Territorio, Universidade de Vigo, 36200, Vigo, Spain aut Geo-Marine Letters Springer-Verlag 27/2-4(2007-06-01), 103-114 0276-0460 27:2-4<103 2007 27 367 https://doi.org/10.1007/s00367-007-0065-3 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/s00367-007-0065-3 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Iglesias Jorge Departamento de Xeociencias Mariñas e Ordenación do Territorio, Universidade de Vigo, 36200, Vigo, Spain aut NATIONALLICENCE 700 1- García-Gil Soledad Departamento de Xeociencias Mariñas e Ordenación do Territorio, Universidade de Vigo, 36200, Vigo, Spain aut NATIONALLICENCE 773 0- Geo-Marine Letters Springer-Verlag 27/2-4(2007-06-01), 103-114 0276-0460 27:2-4<103 2007 27 367 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer