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Volcanes de lodo y deformaciones de origen gravitacional en el Golfo de Cádiz Mud volcanoes and gravity driven processes along the Gulf of Cadiz GIRALDO,HERMOZA and GARCIA-MOJONERO

Authors:

Abstract

Resumen: El área de estudio se encuentra localizada a lo largo del talud continental Atlántico (sector Íbero–Marroquí) al O del Estrecho de Gibraltar. A partir de la interpretación de líneas sísmicas de reflexión (2D) y análisis de datos procedentes de diferentes fuentes públicas (proyectos de investigación, geología regional) se pueden establecer relaciones genéticas entre la ausencia de volcanes de lodo y la presencia de estructuras geológicas asociadas a fenómenos de inestabilidad gravitacional. En esta primera evaluación se postula que dichas estructuras podrían actuar como barreras que impiden el crecimiento y desarrollo de volcanes de lodo ya que podrían controlar las vías de migración de los fluidos relacionados con la expulsión de material arcilloso hacia el fondo marino. Estas estructuras geológicas gravitacionales ham podido producirse durante el Cuaternario y a lo largo de ellas se pueden interpretar, a partir de líneas sísmicas, sectores en extensión (fallas normales) como sectores en compresión (fallas inversas tipo toe-thrust). Abstract: The studied area is located along the Atlantic continental slope (Moroccan–Iberian margin) to the W of the Gibraltar Straits. Preliminary results obtained from interpretation of 2d reflexion seismic lines and compilation of different public sources (Scientific Projects , regional geology) would indicate that there is some relationships between the absence of mud volcanoes phenomena along the slope and the presence of geological structures associated to gravitational instability processes. In this first evaluation it can be considered that these gravity-driven structures would act as barriers for the growth and development of mud volcanoes that control fluids migration pathways related with the mud mobilization through sea floor along the slope. The gravity-driven structures here described seem to have been developed during Quaternary times. Along the area different structural styles can be interpreted from 2d seismic lines: normal faulting (extensional) and reverse faulting/toe-thrust type (compressive).
Introduction
“Extensional” tectonics
“Gravitational” deformation
Mud-diapirism
Conclusions
Volcanes de lodo y
deformaciones de origen
gravitacional en el Golfo de Cádiz
C.Giraldo, W. Hermoza y C.García-Mojonero
Exploración / Dpto. de Geología
www.eosnap.com
Open
Resumen
El área de estudio se localiza al oeste del Estrecho de Gibraltar (sector
Íbero Marroquí).
A partir de la interpretación de líneas sísmicas de reflexión (2D) se
postulan relaciones entre la ausencia de volcanes de lodo y la
presencia de estructuras de inestabilidad gravitacional.
Los «despegues» gravitacionales podrían actuar como barreras que
impiden el crecimiento y desarrollo de volcanes de lodo.
Dichas estructuras podrían controlar las vías de migración de los
fluidos relacionados con la expulsión de material arcilloso.
Las deformaciones gravitacionales han ocurrido durante el
Cuaternario y a lo largo de ellas se interpretan sectores en extensión
(fallas normales) como sectores en compresión ( “toe-thrusts”).
Open
Gutscher et al., 2009
Contenido
1. Geología regional
2. Volcanes de lodo
3. Deformaciones gravitacionales
4. Interpretación
5. Conclusiones preliminares
Open
Gutscher et al., 2009
Contenido
1. Geología regional
2. Volcanes de lodo
3. Deformaciones gravitacionales
4. Interpretación
5. Conclusiones preliminares
Open
Gutscher et al., 2009 10 W 5 W
35 N
37 N
1.Geología regional
Open
Eurasian plate
African plate
Alborán
microplate
40º N
30º N
Margen convergente
( Mioceneo inferior )
http://www.falw.vu/~andb/iberia/thesispdf/6_Chapter4def.pdf
Placa Africana
Microplaca de
Alborán
1.Geología regional
Placa Euroasiática
Andeweg, 2002
Open
http://www.falw.vu/~andb/iberia/thesispdf/6_Chapter4def.pdf
Placa Africana
Placa Euroasiática
Margen convergente
( Mioceno medio) 1.Geología regional
Andeweg, 2002
Open
http://www.falw.vu/~andb/iberia/thesispdf/6_Chapter4def.pdf
Andeweg, 2002 Placa Africana
Placa Euroasiática
Margen convergente
( Mioceno superior) 1.Geología regional
Open
Zitellini et al., 2009
1.Geología regional
Open
Main tectonic elements
Zitellini et al., 2009
1.Geología regional
Open
Gutscher et al., 2009
Contenido
1. Geología regional
2. Volcanes de lodo
3. Deformaciones gravitacionales
4. Interpretación
5. Conclusiones preliminares
Open
100 Kms
Zitellini et al., 2008
2. Volcanes de lodo
Open
13
2. Volcanes de lodo
Strait of Gibraltar
Medialdea et al., 2009
Lóbulo
Norte
Lóbulo
Sur
Open
Medialdea et al., 2009
50 Km
2. Volcanes de lodo
Open
Sobrepresión en
sedimentos impermeables,
formación de diapiros y
«brechificación» durante el
crecimiento del diapiro.
Explosión de gas.
Importante cantidad de
sedimentos saturados de
gas y otros fluidos alcanzan
la superficie.
Main tectonic elements
2.Volcanes de lodo
Mod. de Mazzini, 2009
Diapiro sobrepresurizado
alcanza profundidad
crítica. La columna
geológica no soporta la
saturación de gas del
diapiro.
Continúa la emanación de
arcilla con alto contenido
de fluidos. El proceso
continúa inclusive en
período de calma.
12
34
Open
Gutscher et al., 2009
Contenido
1. Geología regional
2. Volcanes de lodo
3. Deformaciones gravitacionales
4. Interpretación
5. Conclusiones preliminares
Open
Lee et al., 2004
http://www.mbari.org/news/news_releases/2000/dec15_greene.html
3.Deformaciones gravitacionales
Open
Main tectonic elements
3.Deformaciones gravitacionales
12 Km
Gamberi et al., 2011
Open
Previous structural models
Lee et al., 2004
3.Deformaciones gravitacionales
Open
Alboran A-1 SE
NO
6 seg / TWT
10Km
3.Deformaciones gravitacionales
Open
3.Deformaciones gravitacionales
Open
Gutscher et al., 2009
Contenido
1. Geología regional
2. Volcanes de lodo
3. Deformaciones gravitacionales
4. Interpretación
5. Conclusiones preliminares
Open
100 Kms
Zitellini et al., 2008
4.Interpretación
Open
100 Kms
Zitellini et al., 2008
Volcanes de lodo según Medialdea et al., 2008
4.Interpretación
Lóbulos A y B =
Lóbulos Norte y Sur
( Gutscher et al., 2008)
Open
Main tectonic elements
4.Interpretación
Mod. de Crutchley et al. (2011)
Open
Active gravitational failures @ shelf break edge
4.Interpretación
Open
Gutscher et al., 2009
Contenido
1. Geología regional
2. Volcanes de lodo
3. Deformaciones gravitacionales
4. Interpretación
5. Conclusiones preliminares
Open
Gutscher et al., 2009
Los sistemas gravitacionales activos (lóbulos A y B ) funcionan así: al este
fallas normales de carácter lístrico terminarían hacia el oeste en forma de
«toe-thrusts» y dan origen a irregularidades del fondo marino . La dirección
de transporte gravitacional es hacia el oeste.
Se propone que estas deformaciones afectan parte del olistostroma sin
continuar hacia las series mesozoicas.
Las superficies de deslizamiento dentro del olistostroma Mioceno
probablemente actúan como barreras de migración de fluidos inhibiendo la
migración vertical.
Los fluidos al no poder migrar verticalmente lo hacen de forma lateral y
generan volcanes donde hay ausencia de fallamientos lístricos.
En cuanto a los lineamientos propuestos por Zitellini et al. (2008) creemos
que los mismos podrían corresponder a rampas laterales que
compartimentan el lóbulo B. Por lo tanto se tratarían de rasgos geológicos
someros que afectarían al olistostroma y cobertera Miocena-Pliocena sin
continuar en profundidad hacia el basamento.
5.Conclusiones preliminares
Open
Introduction
“Extensional” tectonics
“Gravitational” deformation
Mud-diapirism
Conclusions
Volcanes de lodo y deformaciones de
origen gravitacional en el Golfo de
Cádiz
C.Giraldo, W. Hermoza y C.García-Mojonero
Exploración / Dpto. de Geología
www.eosnap.com
Open
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