Identification and characterization of fluid escape structures (pockmarks) in the Estremadura Spur,West Iberian Margin |
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| Institution: | 1. Departamento de Oceanografia, Universidade Federal do Espírito Santo, Avenida Fernando Ferrari 514, Vitória, ES29090-600, Brazil;2. Instituto de Pesquisas Jardim Botânico do Rio de Janeiro, Rua Pacheco Leão 915, Rio de Janeiro, RJ22460-030, Brazil;3. Departamento de Biologia Marinha, Instituto de Biologia, Centro de Ciências da Saúde, Universidade Federal do Rio de Janeiro, Ilhado Fundão, CP68011, Rio de Janeiro, RJ21944-970, Brazil;4. Dipartimento di Fisica e Scienze della Terra, Università degli Studi di Ferrara, via Saragat 1, I-44122 Ferrara, Italy;5. Departamento de Estratigrafía y Paleontología, Universidad de Granada, Campus Fuentenueva s/n, 18002 Granada, Spain;1. Instituto D. Luiz, Departamento de Geociências ECT, Universidade de Évora, Colégio Luís António Verney, Rua Romão Ramalho, 59, 7002-554 Évora, Portugal;2. Centro de Geofísica de Évora, Departamento de Geociências ECT, Universidade de Évora, Colégio Luís António Verney, Rua Romão Ramalho, 59, 7002-554 Évora, Portugal;3. Centro de Investigação em Ciência e Engenharia Geológica, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal;4. Senckenberg Naturhistorische Sammlungen Dresden, Museum für Mineralogie und Geologie, Königsbrücker Landstr. 159, D-01109 Dresden, Germany;1. Université de Bordeaux, UMR 5805 EPOC, Bat B18, Allée Geoffroy St Hilaire, 33615 Pessac cedex, France;2. Centre Scientifique et Technique Jean Féger—TOTAL, Avenue Larribau, 64018 Pau cedex, France |
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| Abstract: | Located on the West Iberian margin, between Cabo Carvoeiro and Cabo da Roca, the Estremadura Spur is a trapezoidal promontory elongated in an east-west direction, extending until the Tore seamount. Recently a field with more than 70 pockmarks was discovered in the NW region of the Estremadura Spur outer shelf (Lourinhã Monocline). Pockmarks are the seabed culminations of fluid migration through the sedimentary column and their characteristic seabed morphologies correspond to cone-shaped circular or elliptical depressions. The characterization of these features and the understanding of the associated fluid escape process are the main objectives of this work. Here we characterize these structures to understand their structural and stratigraphic control based on: 1) Seismic processing and interpretation of the high resolution 2D single-channel sparker seismic dataset, 2) Bathymetric and Backscatter interpretation and 3) ROV direct observation of the seafloor.The analysis of the seismic profiles allowed the identification of six seismic units, disturbed by the migration and accumulation of fluids. The Estremadura Spur outer shelf has been affected by several episodes of fluid migration and fluid escape during the Pliocene-Quaternary that are expressed by a vast number of seabed and buried pockmarks. At present, the pockmarks are mainly inactive, as the seabed pockmarks are covered by recent sediments. It is concluded that the migration of fluids to the seabed occurred over the Pliocene-Quaternary, as indicated by the buried pockmarks at different depths below the seabed. The vertical stacking of various pockmarks suggests a cyclical fluid flow activity that can possibly be the result of the eustatic sea level variations and the subsequent changes of the hydrostatic pressure. |
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| Keywords: | Pockmarks Fluid migration Estremadura Spur West Iberian Margin High resolution seismic reflection Bathymetry Backscatter |
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