HR: 11:35h
AN: V11I-06 INVITED     [PDF]
TI: The Plio-Quaternary Volcanic Evolution of Gran Canaria Based on new Unspiked K-Ar ages and Magnetostratigraphy
AU: * Guillou, H
EM: herve.guillou@lsce.cnrs-gif.fr
AF: LSCE -CEA/CNRS, Domaine du CNRS - Bat.12 Avenue de la Terrasse, Gif sur Yvette, 91198 France
AU: Carracedo, J
EM: jcarracedo@ipna.csic.es
AF: University La Laguna, Estacion Volcanologica de Canarias, Tenerife, 38206 Spain
AU: Perez Torrado, F
EM: fperez@dfis.ulpgc.es
AF: University of Gran Canaria, Dpto. FĦsica-GeologĦa. Facultad de Ciencias del Mar, Las Palmas, 35017 Spain
AB: The combined use of radioisotopic dating, magnetostratigraphy and field geology is a powerful tool to provide reliable chronological frameworks of volcanic edifices. This approach has been used to investigate the last two stages of the volcanic evolution of Gran Canaria. Fifty samples were dated using the unspiked K-Ar method and had their magnetic polarity measured both in the field and in laboratory. Ages were compared to their stratigraphic positions and magnetic polarities before accepting their validity. The unspiked K-Ar chronology constrains the timing of lateral collapses, eruption rates and the contemporaneity of different volcano-magmatic stages at Gran Canaria. Our new data set modifies significantly the previous chronological framework of Gran Canaria, especially between 4 and 2.8 Ma. Based on these new ages, we can bracket the age of the multiple lateral collapses of the Roque Nublo stratovolcano flanks between 3.5 and 3.1 Ma .This time interval corresponds to a main period of volcanic quiescence. Calculated eruptive rates during the stratovolcano edification are about 0.1 km3/kyr which is significantly lower than the published estimates. The dating also reveals that the two main last stages are not separated by a major time gap, but that the early stages of the rift forming eruption and the vanishing activity of the Roque Nublo strato-volcano were contemporaneous for at least 600 kyrs. These results support that our combined approach provides a rapid first-pass and reliable geochronology. Nevertheless, this chronology can be amplified and made more precise where necessary through detailed Ar-Ar incremental-heating methods. Samples which should be investigated using this method are the oldest and youngest K-Ar dated flows of each volcanic stage, and samples from stratigraphic sections that hold potential to study the behaviour of the earth's magnetic field during reversals (Gauss-Gilbert transition, Olduvai and Reunion events).
DE: 1035 Geochronology
DE: 1749 Volcanology, geochemistry, and petrology
DE: 8494 Instruments and techniques
DE: 9325 Atlantic Ocean
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2003 Fall Meeting