A Large Late Pleistocene Outburst Flood From Pluvial Lakes Alvord and Coyote Into the Owyhee River, Oregon

Deron Carter
December 2004


A large late-Pleistocene flood traveled into the Owyhee River as a result of a rise and subsequent outburst from pluvial Lake Alvord in southeastern Oregon. Lake Alvord breached Big Sand Gap after reaching an elevation of 1292 m, releasing 11.3 km3 into the adjacent Coyote Basin before stabilizing at an elevation of about 1280 m. Overflow then spilled out of the Coyote Basin through two outlets at 1278 m and into the Crooked Creek drainage of the Owyhee River. The flood created a series of deeply incised canyons, scabland topography and deposited numerous boulder bars containing imbricated clasts up to 4.1 m in diameter. The Alvord and Coyote basins also held older, higher elevation lakes that may have released earlier floods down Crooked Creek. Shoreline features at 1292 m and 1280 m in the Alvord Basin have similar weathering characteristics to the flood deposits observed along Crooked Creek, indicating that most mapped flood features occurred during the late-Pleistocene breach.

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