Geochronology of the mega-landslides of the last million years in Tenerife. Part I A Review and new Ar/Ar ages

Abstract

To date, the ages of the large flank landslides which occurred in Tenerife (Canary Islands) during the last million years have been estimated from the ages of the volcanic deposits chronologically related to the landslides, although very scarce data made expressly for this specific purpose are available. In order to get a more precise estimation of these ages, the bibliographical data previously published (1972-2019) on the age of subaerial and submarine volcanic deposits related to the megalandslides of Icod or Las Cañadas, La Orotava, Güímar and Micheque or Acentejo have been collected and reviewed. In addition, new Ar/Ar age determinations from rocks obtained inside the galleries crossing the filling of the landslide valleys of La Orotava, Güímar and Micheque are shown, including some age determinations of the lava flows underlying the landslide debris deposits (‘mortalón’). As a result, we have obtained the following representative ages for the Tenerife landslides: Icod: ~170 ka; La Orotava: ~560, ~530 y ~500(?) ka; Güímar: ~830 ka; and Micheque: 810-830 ka. In the case of the La Orotava landslide, the new age data suggest the occurrence of several overlapping landslides with time intervals of tens of thousands of years. This hypothesis represents a new approach to the study of flank instability processes in volcanic islands, and new scenarios to interpret landslide ages data. On the other hand, it also implies a greater complexity in the landslide mechanisms, and a greater recurrence of the volcanic megalandslides. In Part II of this paper (Ferrer et al., 2020–this volume), new data related to the age, mechanisms and development of Tenerife landslides are presented and discussed, as complementary information.