Additional evidence supports a timescale exceeding 100,000 years for the Guliya ice cap, Tibetan Plateau

The oxygen isotope (δ 18 O ice ) record from a ∼310-meter core drilled on the Guliya ice cap (GIC) in 2015 (GP2015) demonstrates reproducibility with a ∼309-meter core drilled nearby in 1992. Construction of the timescale for a composite of the GIC cores used 10 Be and 36 Cl to locate the 41–thousand year Laschamp geomagnetic excursion and a match to a δ 18 O atm -dated core from the Guliya Summit. Comparison of the δ 18 O record from an Asian Monsoon speleothem with the GIC δ 18 O ice supports a timescale back to 128 thousand years, the oldest known so far from Tibet. The δ 18 O ice record shows orbital variations in phase with June insolation and polar ice core stable isotope records through the last glacial cycle, although the relationship is reversed since the deglaciation. Future investigation is required to resolve this observation. Radiocarbon-dated ice from the glacier margin supports the presence of glacial-stage ice in the GIC. The 36 Cl/ 10 Be ratios in GP2015 confirm that GIC ice is older than 100 thousand years.