Stratigraphic evidence for multiple Holocene advances of Lillooet Glacier, southern Coast Mountains, British Columbia

Abstract

Holocene lateral moraines in the Coast Mountains of British Columbia are commonly composed of multiple drift units related to several glacier advances. In this paper, we document lateral moraine stratigraphy at Lillooet Glacier in the southern Coast Mountains. Five tills, separated by laterally extensive paleosols and layers of large woody debris, were found in three cross-sectional exposures through the northeast lateral moraine and two shallow gullies incised into its steep proximal face. Eighteen new radiocarbon ages constrain the timing of five separate advances of Lillooet Glacier: (1) prior to 3000 14C years BP; (2) ~3000 14C years BP; (3) ~2500 14C years BP; (4) ~1700 to 1400 14C years BP; and (5) during the Little Ice Age (LIA), after 470 14C years BP. The Lillooet Glacier chronology is broadly synchronous with other glacier records from the Coast Mountains. These records collectively demonstrate climate variability at higher frequencies during the late Holocene than is apparent from many paleoecological reconstructions. Reconstructions of glacier fluctuations are often hampered by poor preservation of landforms that predate the extensive LIA advances of the latest Holocene. Our results highlight the potential of lateral moraine stratigraphy for reconstructing these earlier events.