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|Title: ||Seismic characterization of fluid migration and Pockmarks in the Estremadura Spur, West Iberian Margin, Portugal|
|Authors: ||Duarte, Débora|
Magalhães, Vitor Hugo
Menezes Pinheiro, Luis
|Issue Date: ||2017|
|Abstract: ||Recently a field with more than 70 pockmarks was discovered in the NW region of the Estremadura Spur
outer shelf (West Iberian margin), a trapezoidal promontory elongated in an east-west direction, between Cabo
Carvoeiro and Cabo da Roca, extending until the Tore seamount.
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. These features and 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. The 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. The origin of the seep
fluids is still under debate but considering the low-sedimentation rate of the area and the low productivity a deep
source for the fluids is most probable, possibly related with the Jurassic hydrocarbon system. It was concluded
that the migration of fluids to the seabed occurred over the Pliocene-Quaternary in several episodes, as indicated
by the buried pockmarks at different depths.
Acknowledgements: This work was carried out in the framework of the PES project - Pockmarks and
fluid seepage in the Estremadura Spur: implications for regional geology, biology, and petroleum systems
(PTDC/GEOFIQ/5162/2014) financed by the Portuguese Foundation for Science and Technology (FCT). The
seismic dataset was acquired within the PACEMAKER project funded by the European Research Council
(ERC) under the European Union’s Seventh Framework Program (FP7/2007-2013) ERC agreement (226600).
The Instituto Portugues do Mar e da Atmosfera acknowledges support by Landmark Graphics (SeisWorks) via
the Landmark University Grant Program. We thank the Estrutura de Missão para a Extensão da Plataforma
Continental (EMEPC) for allowing me to have access and use the data collected in the Estremadura Spur during
the EMEPC/PEPC/LUSO/2015 cruise and the ROV Luso team. We also thank Prof. Dr. Luis Matias (FCUL &
IDL) for the help with SPW and processing steps.|
|Appears in Collections:||ICT - Comunicações - Em Congressos Científicos Internacionais|
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