New Gravity Map of the Western Galicia Margin:The Spanish Exclusive Economic Zone Project

Abstract

Since 1995, the most intensive mapping of the seafloor off the Spanish coast has been carried out in the framework of the Spanish Exclusive Economic Zone Project (ZEEE).The main objectives of this project are to obtain improved multibeam bathymetric cartography of the areas off Spanish coastlines, and to perform a geophysical survey,well-suited with a 10-knot navigation velocity (some techniques requires lower navigation velocity). The geophysical survey includes gravity, geomagnetism, and low-penetration seismic techniques in order to infer the geological structure of the seafloor. Other oceanographic variables such as current, surface salinity, and temperature profiles, can be recorded without compromising this systematic survey effort. The ZEEE Project has carried out its survey activities for one month every year.Data acquisition is achieved aboard the Spanish R/V Hesperides. Until 1997, surveying efforts concentrated on the Balearic Sea and Valencia Gulf, both in the western Mediterranean Sea. Between 1998 and 2000, the ZEEE Project investigations were conducted offshore the Canary Archipelago. Since 2001, the third phase of the program has been focused on the West Galicia Margin in the northeastern Atlantic Ocean. Survey results on the West Galicia Margin area are of interest for two key reasons. First, there is great scientific interest in the improvement of the knowledge of this non-volcanic rifting margin, since this margin offers good conditions for the study of the processes that take place in this type of geological context,because it is sediment-starved. Second, the obtained results also have major socioeconomic repercussions because they can prove significant to defining the expansion of the Spanish shelf,beyond Spain’s Economic Exclusive Zone distance of 200 nautical miles. All of the gravity data acquired to date on this area have been stored as a database, with the aim of preparing gravity anomaly maps on a scale 1:200,000.The database and gravity anomaly charts from the ZEEE Project will provide the most coherent and complete gravity perspective available for this area. This article describes the efforts and accomplishments of the project to date.