Fig. 2.

(A and B) Pt/Ir (A) and Pt/Al (B) ratios in the GISP2 ice samples across the Bølling-Allerød/YD boundary vary between the chondritic and continental crust values. The only exception is the Pt anomaly with both Pt/Ir and Pt/Al ratios greatly exceeding chondritic and crustal values, with three top points also exceeding Pt/Ir ratios of low-Ir iron meteorites. Such a large fractionation of both Pt/Ir and Pt/Al ratios within the anomaly most likely results from atmospheric processing of the Pt-rich material.