Pockmarks and fluid migration in the Estremadura Spur, Western Iberian Margin.

Abstract

A field with more than 70 pockmarks in the Estremadura Spur outer shelf on the Western Iberia margin is the main focus of research of the PES project. High-resolution seismic reflection profiles and multibeam bathymetry allowed the characterization of the seismic sequence of a Pliocene-Quaternary basin as well as the pockmark field therein. The Pliocene-Quaternary basin developed on top of a folded, most probably, Miocene sequence. The pockmarks are found either sealed within the Pliocene-Quaternary sedimentary sequence or as depressions at the seafloor. Besides the pockmarks, several other seismic evidences of fluid migration and shallow gas accumulations are identified on the seismic dataset. No evidences of pockmarks were found below the Pliocene-Quaternary sequence. The seafloor observations with a ROV on three of those pockmarks show that, although several episodes of fluid migration and escape affected this region at present seepage seems to be mainly inactive.