Adam Beall, Cardiff University, School of Earth and Ocean Sciences, Cardiff, CF24, United Kingdom, Ake Fagereng, Cardiff University, Earth and Ocean Sciences, Cardiff, CF24, United Kingdom, Huw Davies, Cardiff University, Earth and Ocean Sciences, Cardiff, United Kingdom and Fanny Garel, Université de Montpellier, Géosciences Montpellier, Montpellier Cedex 05, France