Publication: Geocronología de los megadeslizamientos de Tenerife del último millón de años. Parte I. Revisión y nuevas dataciones Ar/Ar
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2020
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Instituto Geológico y Minero de España (Madrid)
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Abstract
Hasta el presente, las edades de los grandes deslizamientos de flanco de la isla de Tenerife (islas Canarias) ocurridos en el último millón de años, se han estimado a partir de dataciones de depósitos volcánicos relacionados cronológicamente con los deslizamientos, siendo muy escasas las dataciones realizadas exprofeso para conocer sus edades. Con el propósito de acotarlas en lo posible, se han recopilado y revisado las dataciones disponibles válidas para delimitar las edades de los deslizamientos de Icod, La Orotava, Güímar y Micheque o Acentejo. Así mismo, se presentan nuevas dataciones Ar/Ar realizadas con el fin de ajustar en lo posible la edad de La Orotava, Güímar y Micheque. Por primera vez se publican dataciones en rocas de galerías en el valle de Güímar. Se han datado rocas a muro de los depósitos de los deslizamientos, donde hasta ahora se contaba con un solo dato publicado. Como resultado, se proponen las edades más representativas para los deslizamientos de Icod: ~170 ka; La Orotava: ~560, ~530 y ~500(?) ka; Güímar: ~830 ka; y Micheque: 810-830 ka. Para el valle de La Orotava, las nuevas dataciones permiten proponer la ocurrencia de varios deslizamientos superpuestos con intervalos de decenas de miles de años. Esto supone un nuevo planteamiento de los procesos de desmantelamiento de los flancos de grandes islas volcánicas, y un nuevo escenario para interpretar las dataciones. Pero también una mayor complejidad y recurrencia de los procesos de inestabilidad de los volcanes. Como complemento a los datos aquí aportados, formando la Parte II del presente trabajo, en Ferrer et al. (2020–este volumen) se presentan y discuten nuevos datos relacionados con la edad, desencadenamiento y desarrollo de los deslizamientos.
The review on the ages available in the bibliography (1972-2019) related to the mega-landslides of the island of enerife in the last million years, and the new Ar/Ar ages we have obtained have allowed us to propose the following ages for the landslides of: Icod: ~170 ka; La Orotava: ~560, ~530 y ~500(?) ka; Güímar: ~830 ka; and Micheque: 810-830 ka (Ferrer et al., 2020-this volume). The relationship between the ages of the landslides and the geological and geomorphological evidence that support the flank instability failure processes, based on field observations in outcrops and underground data -from the galleries excavated through the filling of the landslide valley- are presented. The hypothesis of several overlapping flank landslides, with time intervals of at least several tens of thousands of years is proposed, ruling out the occurrence of single processes of massive and instantaneous failure of the insular flank; thus, in the case of the La Orotava valley, an age of around 530 ka is confirmed for a large landslide, as well as the occurrence of other landslides around 560 ka and 500 ka. The relationship and causality between the Icod landslide, the last one that occurred in Tenerife, and the great explosive eruption at the end of the Cañadas cycle, and not the opposite as some authors have suggested, has also been analyzed, concluding that the explosion was a consequence of the landslide, ~170 ka ago. New data and evidence for the Micheque landslide are shown, indicating a Pliocene age for the deep substrate of the La Orotava and Micheque landslides.
The review on the ages available in the bibliography (1972-2019) related to the mega-landslides of the island of enerife in the last million years, and the new Ar/Ar ages we have obtained have allowed us to propose the following ages for the landslides of: Icod: ~170 ka; La Orotava: ~560, ~530 y ~500(?) ka; Güímar: ~830 ka; and Micheque: 810-830 ka (Ferrer et al., 2020-this volume). The relationship between the ages of the landslides and the geological and geomorphological evidence that support the flank instability failure processes, based on field observations in outcrops and underground data -from the galleries excavated through the filling of the landslide valley- are presented. The hypothesis of several overlapping flank landslides, with time intervals of at least several tens of thousands of years is proposed, ruling out the occurrence of single processes of massive and instantaneous failure of the insular flank; thus, in the case of the La Orotava valley, an age of around 530 ka is confirmed for a large landslide, as well as the occurrence of other landslides around 560 ka and 500 ka. The relationship and causality between the Icod landslide, the last one that occurred in Tenerife, and the great explosive eruption at the end of the Cañadas cycle, and not the opposite as some authors have suggested, has also been analyzed, concluding that the explosion was a consequence of the landslide, ~170 ka ago. New data and evidence for the Micheque landslide are shown, indicating a Pliocene age for the deep substrate of the La Orotava and Micheque landslides.