81Kr Dating at the Guliya Ice Cap, Tibetan Plateau

Abstract

We present radiometric 81Kr dating results for ice samples collected at the outlets of the Guliya ice cap in the western Kunlun Mountains of the Tibetan Plateau. This first application of 81Kr dating on midlatitude glacier ice was made possible by recent advances in Atom Trap Trace Analysis, particularly a reduction in the required sample size down to 1 μL STP of krypton. Eight ice blocks were sampled from the bottom of the glacier at three different sites along the southern edges. The 81Kr data yield upper age limits in the range of 15–74 ka (90% confidence level). This is an order of magnitude lower than the ages exceeding 500 ka which the previous 36Cl data suggest for the bottom of the Guliya ice core. It is also significantly lower than the widely used chronology up to 110 ka established for the upper part of the core based on ice δ18O.