( Pacific Northwest National Laboratory g...)An ancient bathtub ring of mammoth fossils

The fossils, in some cases whole skeletons of Mammathus columbi, the Columbian mammoth, were deposited in the hillsides of what are now the Yakima, Columbia and Walla Walla valleys in southeastern Washington, where the elephantine corpses came to rest as water receded from the temporary but repeatedly formed ancient Lake Lewis. PNNL geologists are plotting the deposits to reconstruct the high-water marks of many of the floods, the last of which occurred as recently as 12,000 to 15,000 years ago.

"Now is the perfect time to collect geologic and paleontologic data," said George Last, a senior research scientist at the Department of Energy laboratory in Richland, Wash., whose sideline is researching the ice-age floods. "Winter has eroded the slopes, exposing new evidence. We’re interested in researching any known or suspected mammoth find, to collected additional evidence and to improve documentation of those sites."

Last, PNNL intern Kelsey Winsor and colleagues have identified 62 sites of known or suspected fossil finds and have verified and collected additional material and information at eight of them, including two so far this spring. They presented three seasons?worth of fieldwork Saturday during the Geological Society of America regional meeting at Western Washington University.

"We’re trying to tease out as much information as we can about each and every mammoth find in the mid-Columbia basin, so that we can better understand the impacts that Ice Age floods may have had on the mammoths and other creatures, and in turn learn more about the history of Ice Age flooding."

Geologists suspect that most of the Ice Age floods in eastern Washington originated from glacial Lake Missoula. The lake formed behind ice that dammed th
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Source:DOE/Pacific Northwest National Laboratory