Holocene palaeoenvironmental record preserved in a paraglacial alluvial fan, Sunwapta Pass, Jasper National Park, Alberta, Canada

Abstract

The soil stratigraphy of a 1.5 m section in the distal portion of a paraglacial alluvial fan in Sunwapta Pass, Jasper National Park, has been examined as part of a long-term investigation into Holocene palaeoenvironments of the area. The section is complex and its characteristics are a result of both episodic sediment inputs and pedogenesis. A series of sediments comprising debris-flows and aeolian material including three discrete tephra layers (Mazama, St. Helens Yn, Bridge River) underlie the present day soil. Multiple criteria, including stratigraphy, radiocarbon dates, glass shard morphology, and electron microprobe analysis of glass and titanomagnetite composition, confirmed the identity of the tephras. Most fan development occurred before deposition of Mazama tephra. Pedogenesis has been active on the fan throughout the Holocene. Soils have formed between phases of sediment deposition during periods of greater relative site stability. Soil horizonation is best developed where tephric material has influenced soil chemistry and clay mineralogy leading to the formation of Brunisols. The sequence of events inferred from the Icefield Fan's stratigraphy accord well with the Holocene palaeoenvironmental history inferred from other sites in the Canadian Rockies.