Cosmogenic dating of Late Pleistocene glaciation, southern tropical Andes, Peru

Abstract

We present 30 10 Be dates on three moraines formed by small glaciers in the southern tropical Andes of Peru to determine the timing of the local Last Glacial Maximum (LGM) and subsequent deglaciation. Two terminal moraines indicate that the local LGM ended at 23.5 ± 0.5 and 21.2 ± 0.8 ka, or well before the end of the global LGM (20–19 ka). A recessional moraine perched at the base of a steep valley wall has a 10 Be age of 19.8 ± 0.3 ka, suggesting that glaciers had largely retreated from the area during the earliest stages of the last termination and before the onset of the deglacial CO 2 rise and increase in tropical sea surface temperatures. These ages generally agree with other tropical glacial chronologies and reflect a broad synchroneity between low‐ and high‐latitude deglaciation at the LGM, but the trigger for early deglaciation of the tropics remains unclear.

Bibliographic Information