Figure 1: Overview maps of sample sites and simple exposure ¹⁰ Be ages.

(a) South Greenland overview with coloured boxes marking the four TCN sample sites and black circles marking points of pre-LGM Quaternary data^5,7,36. (b) Uummannaq area with sample sites containing ¹⁰Be and ²⁶Al bedrock data¹⁹. The point marked with an asterisk represents 3 sample sites, which are shown in the top left box. The scale bar is 50 km wide. (c) Sample sites with ¹⁰Be and ²⁶Al bedrock data^20,24,25 from the Upernavik area. The scale bar is 25 km wide. (d) Sisimiut area, covering samples from two sites; the inter-fjord site Itilleq²⁶ (red) and samples from the margins of the local ice cap Sukkertoppen²⁰ (yellow). The scale bar is 50 km wide. The data points shown in (b–d) meet the criteria of being applicable to the MCMC model approach, by having simple exposure ¹⁰Be ages above 20 kyr and a ²⁶Al/¹⁰Be ratio below 7.5. (b–d) Simple exposure ¹⁰Be ages are calculated using Cronus Version 2.3 (ref. 45) and the Lal (1991)/Stone (2000) scaling scheme^40,41. Figure 1 was created using QGIS software⁴⁶. All satellite images are from Landsat8, August 2016, courtesy of the U.S. Geological Survey.