Supporting Information 5

Detailed fission track age data for each sample. 238U refers to the measured 238U concentration for each grain in ppm with SD = 1σ uncertainty. Ns represents the number of counted tracks. Area = the size of the counted area in cm2. Rho s = the spontaneous fission track density. t(Ma) is the calculated fission track age for each grain in Ma with SD = 1σ age uncertainty. Detailed fission track length data for each analysed confined fission track. Length values are given in µm. Azimuth is the angle to the c-axis and Dip is the angle to the surface (both in °). Dpar are given as grain averages with 1σ standard deviations in µm.