The major glacial stages of the current ice age in North America are the Illinoian, Sangamonian and Wisconsin stages. (newworldencyclopedia.org)
At this early stage of knowledge, what was being studied were the glacial periods within the past few hundred thousand years, during the current ice age. (newworldencyclopedia.org)
The current ice age began about 4 × 107 years ago, and gained in intensity during the Pleistocene. (newworldencyclopedia.org)