As of Friday, July 11, 2014
Ancient Cataclysmic Floods were the Ice Age Floods that preceded the Missoula Floods in the Pacific Northwest. Ancient Cataclysmic flooding initiated in the Early Pleistocene. Erika Medley and Scott Burns (Department of Geology, Portland State University) studied a total of 29 ancient cataclysmic flood sites, visiting all 14 previously studied ancient sites and four Missoula Flood quarries. They also found 11 new sites.
Scott Burns will give a talk about this research Saturday, July 12, at 1 p.m., in the upstairs reading room at the Hood River Library, 502 State Street. The talk is free to everyone.
Medley and Burns analyzed calcrete paleosols to provide relative age dates for flood deposits. Missoula Flood gravel pits were sampled in order to examine the degree of calcrete development in flood deposits of known ages. Calcrete paleosols at sites with evidence for older floods were all analyzed.
Sixteen field sites show evidence for Early Pleistocene flooding, preserved in all six provinces. There are 26 field sites with evidence for Middle Pleistocene flooding. Eleven of those 26 sites also show evidence for Early Pleistocene floods. Evidence for Early and Middle Pleistocene floods is present over a wide distribution of elevations from 117 to 524 meters.
All of the Missoula Flood deposits tested contain Stage 1 calcrete soil development. Eight sites have paleosols with Stage II development (3-12% CaCO3). Five sites have paleosols with Stage II+ development (12-17% CaCO3). Fourteen sites have paleosols with Stage III development (17-35% CaCO3). One site has a paleosol with Stage III+ development (35-50% CaCO3). A special section will discuss the Highway 197 site outside of The Dalles where they now describe eight paleosols.