Implications for the early shield-stage evolution of Tenerife from K/Ar ages and magnetic stratigraphy

The combined use of field geology, radioisotopic dating and magnetic stratigraphy applied to the old shield volcanoes of Tenerife provides a reliable time framework for the early, shield-stage evolution of the island. The greater part of this new set of ages, obtained from sequences of lava flows is in agreement with the astronomical polarity time scale. This approach illustrates that previous K-Ar data collected without a comprehensive stratigraphy should be viewed with caution, and in some cases discarded altogether. The shield volcanoes of Tenerife encompass a relatively small number of magnetozones, an observation consistent with the relatively short periods of growth shown by the new ages (1-2 my). The island was constructed by the aggregation of three successive shields: the Roque del Conde (Central shield), between about 11.9 and 8.9 Ma, and the Teno (6.2-5.6 Ma) and Anaga (4.9-3.9 Ma) volcanoes. This new oldest subaerial age of Tenerife fits with the others obtained in the Canaries in a clear west to east monotonous age progression, one of the main restrictions for hotspot-related island chains.