CALICHE PALEOSOLS OF ANCIENT CATACLYSMIC FLOOD DEPOSITS OF THE ICE AGE FLOODS, WASHINGTON

The Missoula Floods left erosional and depositional features behind in eastern Washington, now termed the scablands. At least 89 floods occurred when Glacial Lake Missoula’s ice dam repeatedly ruptured and re-formed between 15 to 18 thousand calendar years ago, with 40 of the floods reaching Wallula Gap (Allen et al., 2009). Medley and Burns have hypothesized about older floods throughout the Quaternary. Much of the evidence of these older deposits have been wiped out by the Missoula Floods. However, in some locations, caliche paleosols overlie much older flood deposits, termed the Ancient Cataclysmic Flood deposits. Stages 1 through 6 of calcium carbonate development take longer than 15 thousand years to form in these deposits, dating them earlier than the Missoula Floods. One example of investigating these paleosols was done in the Avery gravel pit located 10 miles east of The Dalles in Washington. It provides an exposure of flood deposits in three stratigraphic layers. Samples collected from the layers were tested for percentages of calcium carbonate. The bottom layer contained 1.62 percent calcium carbonate and the middle contained 0.95 percent, confirming that the paleosol is Stage 1 caliche and an Ancient Cataclysmic Flood deposit. The top layer is a Missoula Flood deposit and contains less than 0.5 percent calcium carbonate.