Reconstructing the recent failure chronology of a multistage landslide complex using cosmogenic isotope concentrations: St Catherine's Point, UK

• Cosmogenic isotopes are used to date sequential landslide events.
• Our understanding of failure mechanism is used to modify topographic shielding calculations for the earlier stage.
• The most recent event at St Catherine's Point is dated to 1064 ± 348 (± 1 σ) 10Be years ago.
• An earlier failure is dated to 3471 ± 348 10Be years ago.
• The St Catherine's Point landslide complex was reactivated by Holocene relative sea-level rise.

The pre-existing multistage landslide complex at St Catherine's Point comprises a series of large rotational and translational failures that form the western section of the Isle of Wight Undercliff, UK. Cosmogenic beryllium and aluminum concentrations extracted from chert samples of the Upper Greensand are used to date the most recent sequential failure events. We use our understanding of the failure mechanics and landslide geomorphology to produce a cosmogenic exposure model that incorporates pre-failure topography into our shielding calculations. This method allowed us to date two successive landslides at the site using 10Be, the most recent of which occurred ~ 1064 ± 348 (± 1 σ) 10Be years ago, much more recently than was previously thought. An earlier failure event is dated at ~ 3471 ± 348 10Be years, supporting the hypothesis that the St Catherine's Point landslide complex was reactivated by relative sea-level rise at the end of the Holocene Climatic Optimum period.