A HOLOCENE RECORD OF LARGE-SCALE DISTURBANCE EVENTS IN THE UINTA MOUNTAINS, UTAH, USA

Holocene climate variability has resulted in a dynamic disturbance history in the Uinta Mountains. A 12,000-year-long-lake-sediment record provides evidence of large magnitude fire and flood events during the Holocene. The frequency of fire increased during the mid-to-late Holocene (~3000 cal yr BP), but then decreased in the last millennia. As fire frequency decreased the magnitude of fire and flood events have increased. The importance of large magnitude flood events is also explored in terms of frequency and magnitude. The recent (20^th century) catastrophic draining of this montane lake that was dammed by a recessional moraine provides a recent example of an extreme disturbance event. The study site today, currently being colonized by lodgepole pine, affords a unique opportunity with excellent preservation of fossil pollen and paleobotanical remains to explore the magnitude and frequency of disturbance in this setting. Results from the fossil charcoal, pollen and lithologic analyses are compared with centennial-scale late-Holocene climate records to evaluate the influence of climate ion disturbance, including the Little Ice Age and Medieval Climate Anomaly. These findings provide context for understanding recent large magnitude disturbance events in the Uinta Mountains.