Tectonics and mud volcano development
in the Gulf of Cádiz
T. Medialdea , L. Somoza, L.M. Pinheiro, M.C. Fernández-Puga J.T. Vázquez, R. León, M.K. Ivanov, V. Magalhaes, V. Díaz-del-Río and R. Vegas
Volume 261, Issues 1-4, 1 June 2009, Pages 48-63
EUROMARGINS: Imaging, monitoring, and modelling the physical, chemical and biological processes in the European passive continental margins
Many structures associated with fluid escape, including mud volcanoes, mud-carbonate mounds, pockmarks and slides, have been identified and characterized in the Gulf of Cádiz.
Most of the mud volcanoes following NE–SW and NW–SE main trends are found at 350–2000 m depth in the eastern domain of the Gulf of Cádiz, which corresponds to the Betic–Rifean Margin.
Scattered mud volcanoes have also been recognized on the lower slope at 2300–3900 m depth.
The major tectonic structures are thrust faults, extensional faults, strike-slip faults and diapirs. All these tectonic structures have provided escape pathways for overpressured material and fluids or have favoured upward fluid movement along the sedimentary column and eventually the build up of mud volcanoes.
In this work we present images of the mud volcano plumbing systems and the relationship between regional tectonics and mud volcano development.
Seismic profiles acquired during the TASYO 2000 and MVSEIS/TTR-15 cruises are used to image and interpret the link between the mud volcano edifices and the subsurface tectonic structures.
Keywords: mud volcanoes; hydrocarbon seeps; fluid venting; diapirism; tectonics; Gulf of Cadiz
Fluid escape pathways and tectonics
Triggering mechanisms for fluid expulsion
Mud volcano systems and diapirism
Fig. 1. A) Map of the Gulf of Cádiz (modified from Medialdea, 2007) based on interpretation of MCS lines with the location of main outcropping and very shallow diapirs, faults, mud volcanoes and mud-carbonate mounds. FSb: Subbetic Front; FF: Flysch Front. Mud volcanoes recently discovered after Somoza et al. (2008). B) Line-drawing derived from the MCS profile TASYO 1 that crosses the Gulf of Cádiz. See Fig. 1A for location.
Fig. 2. Simplified geological map of the Gulf of Cádiz showing the main fronts of the AUGC (modified from Medialdea et al., 2004) and the mud-carbonate mounds and mud volcanoes identified in the Gulf of Cádiz. Mud volcano data taken from Ivanov et al. (2000), Gardner (2001), Pinheiro et al. (2003), Somoza et al. (2003) and Schwenk et al. (2006). Mud-carbonate mounds location taken from Díaz-del-Río et al. (2003).
Fig. 3. Location of TASYO multichannel seismic lines and previous surveys (Anastasya99 and Anastasya00) in the Gulf of Cádiz.
Fig. 4. A) Map of the shale/salt diapirs and NE–SW trending diapiric ridges on the upper–middle slope of the Gulf of Cádiz (Modified from Fernández-Puga et al., 2007); B) Bathymetric map of the Lolita salt diapir obtained with multibeam data; see Figs. 1A and 4A for location; C) Multichannel seismic profile across the Lolita salt structure where the diapir can be observed rising from below the AUGC.
Fig. 5. Multichannel seismic line TASYO 8 across the Doñana and Guadalquivir Diapiric ridges. See Fig. 2 for location. Inset shows location of Fig. 6 and Fig. 7.
Fig. 6. A) 3D bathymetric image of the Gades mud volcano. B) Detail of the multichannel seismic line TASYO 8 across the Gades mud volcano. See Fig. 5 for location.
Fig. 7. A) Detail of the multichannel seismic line TASYO 8 across the Guadalquivir Diapiric Ridge, close to the Cornide and Ibérico mud-carbonate mounds. See Fig. 2 for location; B) Sparker profile of the Ibérico carbonate-mud mound; C) Underwater picture of the carbonate chimneys lying at the sea floor taken during the Anastasya OO cruise.
Fig. 8. Multichannel seismic line TASYO 1 crossing the Captain Arutyunov and Tasyo mud volcanoes. See Fig. 1 and Fig. 2 for location and 1B for interpretation. Inset shows location of Fig. 9.
Fig. 9. Detail of the multichannel seismic line TASYO 1 across the Tasyo mud volcano and the corresponding line-drawing, where the whole mud volcano system can be observed, including the stack of two bicones. See Fig. 2 and Fig. 8 for location.
Fig. 10. A) Detail of the multichannel seismic line TASYO 1, shown in Fig. 9, across the Tasyo mud volcano, where the stack of two bicones is displayed. B) Multibeam image of the Tasyo mud volcano (constructed with data from TASYO and GAP cruises, Kopf et al., 2004).
Fig. 11. Interpreted side scan sonar image (OKEAN) and high resolution seismic line (PSAT-271) from the TTR15 cruise on the Moroccan margin across a NW–SE right-lateral strike-slip fault, showing its possible intersection with a thrust fault; A) and B) Single-channel seismic reflection profile PSAT 271; C) corresponding interpreted 9.5 kHz OKEAN side scan sonar profile. Inset in (C) shows uninterpreted data. D: mud(?) diapir. See Fig. 2 for location.
Fig. 12. 3D bathymetric image of the Almanzor mud volcano discovered during the MVSEIS08 Cruise. The mud volcano is located on the Moroccan margin on the same strike-slip fault displayed in Fig. 11. See Fig. 2 for location.
Fig. 13. A) Western segment of the multichannel seismic line TASYO 1 crossing the Semenovitch, Soloviev and Carlos Texeira mud volcanoes. See Fig. 1 and Fig. 2 for location. Insets show location of detailed profiles B) and C) where thrust faults related to the mud volcanoes are indicated.