Please cite this article as: Medialdea, T., et al., Tectonics and mud volcano development in the Gulf of Cádiz, Mar. Geol. (2008), doi:10.1016/j. margeo.2008.10.007
lINK: http://www.igme.es/INTERNET/SIDIMAGENES/143000/120/143120_0000011.PDF
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, strikeslip 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.
− There is a close relationship between fluid escape structures and tectonic structures determined by the development of the Betic– Rifean orogen and the neotectonic activity that took place under the convergent regime between the African and Eurasian plates.
In the Gulf of Cádiz tectonics related to the compressive regime
represents the major control for fluid migration.
− It is inferred from seismic images that mud volcanoes are tectonically controlled by structures resulting from the NW compressional regime.
CONCLUSIONS
There is a close relationship between fluid escape structures and tectonic structures determined by the development of the Betic– Rifean orogen and the neotectonic activity that took place under the convergent regime between the African and Eurasian plates.
In the Gulf of Cádiz tectonics related to the compressive regime
represents the major control for fluid migration.
− It is inferred from seismic images that mud volcanoes are tectonically controlled by structures resulting from the NW compressional regime.
Diapirism is a key factor in mud volcano development, as can be concluded from seismic images, in which mud volcanoes are always found above or associated with diapirs at different burial depths.
It has been determined that not only marly diapirism related to the AUGC is important, but also salt diapirism.
Diapirs and faults allow overpressured muds and fluids to be extruded to the surface.
In the first step mud volcanoes and fluid venting are related to diapiric development. In each case the subsurface mud volcano system appears to be different.
Whereas on the lower slope mud volcanoes are isolated, without any noticeable dominant trend, on the Betic Rifean margin mud volcanoes are clustered in several fields and in groups forming linear zones related toW–E toWNW–ESE dextral strike-slip faults or thrust faults and diapirs.
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