The Plio-Quaternary volcanic evolution of Gran Canaria based on new K-Ar ages and magneto stratigraphy

The combined use of radiometric dating (51 new unspiked K-Ar ages), magnetostratigraphy and field geology establishes a new time framework for the last two stages of the volcanic evolution of Gran Canaria. Most of the dated samples have ages coherent with their stratigraphic positions and magnetic polarities. Our new set of data extends the end of the Roque Nublo (RN) group, one of the main posterosive stages of Gran Canaria which started about 4.9 Ma ago, to ages as young as 2.87 Ma. This is about 0.7 Ma younger than previously thought. Moreover, the dating of samples collected in well-defined stratigraphic sequences supports the contemporaneity of the early stages of the post-Roque Nublo group and the vanishing activity of the Roque Nublo stratovolcano between 3.7 and 2.9 Ma. The multiple lateral collapses of the Roque Nublo stratovolcano occurred during this period between 3.5 and 3.1 Ma which corresponds to a main period of volcanic quiescence. After 2.9 Ma, the effusive activity propagated along a well-defined NW-SE rift until about 1.5 Ma, shifting progressively from a rifting propagation to platformforming lavas. Thereafter, the activity is very disperse and belongs to the Brunhes period, with most of it before 500 ka. (C) 2004 Elsevier B.V All rights reserved.