 This date was based in examination of fossils by C. R. Eastman, who thought them to be similar to those found in the Florissant Formation of Colorado, which at the time was also considered Miocene.This age was retained in the 1928 work of Edward W. Berry, who included the Klondike Mountain Formation fossil lakebeds as part of the Latah Formation.The age of the Formation has been revised in the following hundred years, with Roland W. Brown identifying the deposits as being older than the Latah Formation in 1936.