TY - JOUR A1 - Becerril, Laura A1 - Ubide, Teresa A1 - Sudo, Masafumi A1 - Marti, Joan A1 - Galindo, Ines A1 - Gale, Carlos A1 - Maria Morales, Jose A1 - Yepes, Jorge A1 - Lago, Marceliano T1 - Geochronological constraints on the evolution of El Hierro (Canary Islands) JF - Journal of African earth sciences N2 - New age data have been obtained to time constrain the recent Quaternary volcanism of El Hierro (Canary Islands) and to estimate its recurrence rate. We have carried out Ar-40/Ar-39 geochronology on samples spanning the entire volcanostratigraphic sequence of the island and C-14 geochronology on the most recent eruption on the northeast rift of the island: 2280 +/- 30 yr BP. We combine the new absolute data with a revision of published ages onshore, some of which were identified through geomorphological criteria (relative data). We present a revised and updated chronology of volcanism for the last 33 ka that we use to estimate the maximum eruptive recurrence of the island. The number of events per year determined is 9.7 x 10(-4) for the emerged part of the island, which means that, as a minimum, one eruption has occurred approximately every 1000 years. This highlights the need of more geochronological data to better constrain the eruptive recurrence of El Hierro. (C) 2015 Elsevier Ltd. All rights reserved. KW - Ar-40/Ar-39 KW - C-14 KW - Eruptive recurrence KW - El Hierro KW - Canary Islands Y1 - 2016 U6 - https://doi.org/10.1016/j.jafrearsci.2015.10.012 SN - 1464-343X SN - 1879-1956 VL - 113 SP - 88 EP - 94 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Scharf, Andreas A1 - Handy, Mark R. A1 - Schmid, Stefan M. A1 - Favaro, Silvia A1 - Sudo, Masafumi A1 - Schuster, Ralf A1 - Hammerschmidt, Konrad T1 - Grain-size effects on the closure temperature of white mica in a crustal-scale extensional shear - zone - Implications of in-situ Ar-40/Ar-39 laser-ablation of white mica for dating shearing and cooling (Tauern Window, Eastern Alps) JF - Tectonophysics : international journal of geotectonics and the geology and physics of the interior of the earth N2 - In-situ Ar-40/Ar-39 laser ablation dating of white-mica grains was performed on samples from the footwall of a crustal-scale extensional fault (Katschberg Normal Fault; KNF) that accommodated eastward orogen-parallel displacement of Alpine orogenic crust in the eastern part of the Tauern Window. This dating yields predominantly cooling ages ranging from 31 to 13 Myr, with most ages clustering between 21 and 17 Myr. Folded white micas that predate the main Katschberg foliation yield, within error, the same ages as white-mica grains that overgrow this foliation. However, the absolute ages of both generations are older at the base (20 Myr) where their grain size is larger (300-500 mu m), than at the top and adjacent to the hangingwall (17 Myr) of this shear zone where grain size is smaller (<100-300 mu m). This fining-upward trend of white-mica grain size within the KNF is associated with a reduction of the closure temperature from the base (similar to 445 degrees C) to the top (<400 degrees C) and explains the counter-intuitive trend of downward-increasing age of cooling in the footwall. The new data show that rapid cooling within the KNF of the eastern Tauern Window started sometime before 21 Myr according to the Ar-40/Ar-39 white-mica cooling ages and between 25-21 Myr according to the new Rb/Sr white-mica ages, i.e., shortly after the attainment of the thermal peak in the Tauern Window at similar to 25 Myr ago. These new data, combined with literature data, support earlier cooling in the eastern part of then Tauem Window than in the western part by some 3-5 Myr. (C) 2016 Elsevier B.V. All rights reserved. KW - Eastern Alps KW - Ar-40/Ar-39 laser ablation KW - Closure temperature KW - Orogen-parallel lateral extrusion KW - Rapid exhumation/cooling Y1 - 2016 U6 - https://doi.org/10.1016/j.tecto.2016.02.014 SN - 0040-1951 SN - 1879-3266 VL - 674 SP - 210 EP - 226 PB - Elsevier CY - Amsterdam ER -