5 Exceptional Floods in the Cordillera

Wednesday, 15 May 2024
8:00 AM - 12:00 PM
Cedar Ballroom

ANCIENT CATACLYSMIC FLOODS OF THE ICE AGE FLOODS OF THE PACIFIC NORTHWEST

Paper number: 5-13
Program: Theme Sessions
Time: 11:40 AM – 12:00 PM

Authors

  • Scott Burns Presenting Author
    Portland State UnivDept Geology, Portland, OR
  • Erica Medley
    South Pacific Division, Dam Safety Production Center, Sacramento, CA

Abstract

A study of 41 sites in Oregon and Washington was conducted to examine Ice Age Flood deposits older than the traditional Missoula Flood deposits (15-19 Ka in age). Half of the sites were already in the literature and half of them were new in this study. Each site was characterized for the stages of calcrete development from Stages I-V using the system of Mike Machette. The Missoula Flood deposits do not have the calcrete soils, but the older Ancient Cataclysmic Flood sites do have these white deposits. Fifteen Early Pleistocene sites and 26 Middle Pleistocene soils are characterized showing that these Ice Age Floods occurred throughout the Quaternary. Six sites will be discussed with the number of paleosols at each site in parentheses: Potholes Coulee (5); Reese Coulee (8); Yakima Bluffs (7 with 10 rhythmites), Othello Canal (1 stage 5 paleosol 2 meters thick), Rulo Outcrop (8), and the Dalles (5 paleosols with reversed magnetism). The overall conclusion is that Ice Age Floods occurred throughout the Quaternary with the most famous ones being the last set and called the Missoula Floods.

Geological Society of America Abstracts with Programs. Vol. 56, No. 4

doi: 10.1130/abs/2024CD-399313

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