Figure 3.

(a) Evolution of the atmospheric content of ¹²⁹Xe derived from the decay of ¹²⁹I with time. The non-corrected amount gave a closure age of 98 Ma for the I–Xe system. After correction for subsequent loss, the age becomes 41 Ma. (b) Evolution with time of the ratio of radioactive products in the atmosphere (¹²⁹Xe(I) and ¹³⁶Xe(Pu)). The non-corrected ratio gave a closure age of 66 Ma for the I–Pu–Xe system. After correction, the age becomes 34 Ma, in agreement with the time of closure of the I–Xe system and with the closure age of the mantle given by the mantle samples [4,32].