Late Quaternary glaciations in the Cogarbu valley, Bhutanese Himalaya

Abstract

ABSTRACTThis study investigates the late Quaternary glacial history of the Cogarbu valley on the northern slopes of the Bhutanese Himalaya using 10Be surface exposure dating. Five major glacial events were constrained based on 28 10Be exposure ages. The equilibrium line altitude (ELA) of the oldest and most extensive glacial event (M5–M9) is ∼489 m lower than the present, followed by four other events (M4, M3, M2 and M1) with ELA depressions of ∼452, ∼200, ∼76 and ∼42 m, respectively. The exposure ages of the oldest glacial event (M5–M9) are ∼23.4–19.1 ka, corresponding to the global Last Glacial Maximum (gLGM). The second (M4, ∼15.8 ka) and the third oldest events (M3, ∼11.5 ka) coincide with the Heinrich‐1 and Younger Dryas event, respectively. The fourth oldest glacial event (∼1.2–0.82 ka) occurred during the Late Holocene. The latest glacial event (∼0.77–0.53 ka) represents the Little Ice Age glacial advances. These glacial events are broadly synchronous with those from other regions across the monsoon‐influenced Himalaya. All these events occurred during the cold periods, despite relatively dry conditions. It appears that temperature is the major factor driving glacial fluctuations since the gLGM in the Bhutanese Himalaya.