Lacustrine Sediment Record of Multiple Quaternary Lava Dams on the Owyhee River, Southeastern Oregon

Caitlin Anne Orem
May 2010

Abstract

Multiple lava dams and correlating lakes impacted the Quaternary evolution of the Owyhee River. Sediment records from lava-dammed lakes were investigated to understand effects of the West Crater (WC) lava dam (~70 ka), the Saddle Butte 2 lava dam (~144 ka), and the Bogus Rim lava dam (~1.9 Ma). Evidence from the WC lava dam and related features indicates that dam duration consisted of five stages (1) dam and lake formation at ~70 ka; (2) dam overflow and lake sedimentation from ~70–46 ka; (3) removal of lava dam and lake termination from ~46 ka to at least 36 ka; (4) incision of underlying units from ~36–15 ka; and (5) incision to modern river level from ~15–0 ka. The WC lava dam lasted ~24,000 yrs and ~31,000 yrs of incision was needed to reestablish the river. This information gives perspective on the effects of lava dams on fluvial landscapes.

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