Eurasia–Africa Plate Boundary Affected by a South Atlantic Asthenospheric Channel in the Gulf of Cadiz Region?

Abstract

The Gulf of Cadiz has been affected by a long and complex geodynamic evolution. The lithospheric structure is poorly understood in this region, and it also shows a diffuse seismicity, spanning over a broad area. The Canary Archipelago has been extensively studied. Nevertheless, there are fundamental topics that are still under debate. No studies have addressed or suggested the possibility of a plausible geodynamic connection between both remarkable locations. In this study we integrate total tectonic subsidence (TTS), Curie point depth (CPD), Bouguer gravity anomaly, and seismic information. TTS shows the existence of a basement bulge in the area of the Canary Archipelago that extends to the north, and in the area of Madeira Island, which extends in a more subtle way to the north, too. Likewise, the CPD reaches the shallowest values in the same location at the Canary Archipelago. These two aspects suggest a cause-effect relationship between TTS and CPD at this specific area. Gravity data and CPD show a linear feature, which links the NW of the Canary Archipelago and the Gulf of Cadiz. The data we manage in this work show remarkable clues as: (a) the absence of a similar signal in the TTS, (b) the fact that CPD it is rather constant along this track, (c) CPD amplitude also almost doubles the values obtained on Canary Archipelago, and (d) the existence of a clear correlation between seismogenic depths and CPD, which points to the existence of a correlation between seismicity and the thermal architecture of the lithosphere. All of these evidences support the presence of a lithospheric thinning between Canary Islands and Gulf of Cadiz area, and in turn, the presence of an asthenospheric channel which feeds and alter locally the Eurasia–Africa Plate Boundary.