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 by Edward W. Berry (1929), 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 (1936) identifying the deposits as being older than the Latah Formation. In a later written communication circa 1958, Brown again revised the age still older, stating the fossils found in the area of Mount Elizabeth indicated an Oligocene age. This age was used by Parker and Calkins (1964) for work on the Curlew Quadrangle of Ferry County. Work by Pearson and Obradovich (1977) refined the Sanpoil Volcanics age to between , and a general age estimate for the Klondike Mountain Formation between and . Since then the fossil-bearing strata of the Formation have been radiometrically dated, to give an estimate of the Ypresian, the mid stage of the early Eocene,, which was revised to an oldest age estimate of which given based on detrital zircon isotopic data published in 2021. Lithology Parker and Calkins (1964) noted the association of the Klondike Mountain Formation with the gold and silver deposits of the Republic District and suggested it as a potential host to more ore deposits in the Curlew Quadrangle. The epithermal gold deposits occurring in the Sanpoil volcanics terminate directly below the unconformity where the volcanics contact the base of the Klondike Mountain Formation or sometimes penetrate into the Formation's lowest unit. Hydrothermal sinter deposits are known from the lowest portions of the Formation and are thought to represent hydrothermal eruption areas. In general the lower portions of the Formation have a large amount of hydrothermal alteration, and areas around vents are rich in pyrite and silica. two products of natural hydrothermic sintering. The areas above that show a transition to mudstones, siltstones and sandstones grading from fine-grained material into coarser materials moving up the strata column. The finely-bedded stones show the greatest numbers of fossils and the finest preservation of details. Paleoenvironment and paleoclimate The lake bed sediments preserve a diverse array of plants, insects, and fishes, notably the biota called the Republic flora. The Okanagan lake system, which includes the Klondike Mountain Formation, has been classified as one of the great Canadian lagerstätten. The area