undifferentiated rock units

Paleontology and geology

In the Quaternary, volcanic eruptions and earthquakes continued in Yukon Territory as the continental and oceanic plates slid past each other to the southwest. This activity also uplifted islands and mountains in the southwestern part of the territory. Glaciers developed in these mountains and swept down over Yukon several times. They carved out valleys in the mountains, scraped up rocks, and deposited them when they melted. Occasionally, ice blocked the normal flow of water, creating large lakes such as Lake Champagne, or altering the course of a river, like the Yukon River, which originally flowed south. Some areas in the north and center of the territory were left unglaciated, and they contain the some of the most abundant and diverse fossils of Ice Age animals in the country. Many different grazing animals, such as horses, camels, mammoths, muskox, and ground sloths roamed the tundra, steppe, and pine forests. They were hunted by the American lion, short-faced bear, scimitar cat, and early wolves. Smaller rodents, shrews, and rabbits lived here, along with many shorebirds, ducks, and geese that spent their time in lakes filled with fish.