Figure 4: A) The Valanginian/Hauterivian boundary (arrowed) in the Arnayon valley, east of the Pré Guitard pass, La Drôme, SE France (22/05/2024). B) The author and a visiting group of third year students from the Université de Bretagne occidentale (Brest, Finistère) at the Hauterivian GSSP in La Charce, La Drôme, SE France (22/05/2016). C) The Hauterivian GSSP (arrowed) at La Charce (12/05/2020).