Holocene Glacier Advances in the Topolovaya Valley, Bystrinskiy Range, Kamchatka, Russia, Dated by Tephrochronology ana Lichenometry

Abstract

Two moraine sequences in one of the ice-free cirques in Topolovaya valley located above the cirque threshold at altitudes of about 700–800 m are dated by tephrochronology and lichenometry. Prominent advances of the glaciers occurred twice prior to 7600–7700 yr BP; and at approximately 2200–2600, 1900–2300(?), and 800–1100(?) lichenometric (L) years ago. The glacier fluctuations over the Holocene were of small magnitude (length of glaciers did not exceed 1 km, equilibrium-line altitude [ELA] varied between 850 and 1100 m) as compared with those of the Last Glacial Maximum (8 km long glacier, ELA at approximately 600 m). Early Holocene advances were more extensive than Neoglacial advances. Because of the great variability of modern ELAs in Kamchatka (from 2700–2900 to 600–700 m), the reconstructed ELAs in Topolovaya valley should be considered as representative only for southern Kamchatka. A hypothesis for formation of rock glaciers from lateral moraines is considered in the paper. A new Rhizocarpon geographicum (L.) DC growth curve is established, which may be applied to dating other glacial deposits in Kamchatka.