The Paleontology of North America

the Quaternary - 1.8 Million Years Ago to Present

World Paleogeography: Throughout the Quaternary, most of the continents have followed the same movements they began in the Late Tertiary. India and Australia have continued their movement north, adding to the Himalayas in Asia and the volcanic islands and eruptions in the South Pacific. Africa and Europe have continued drifting farther from North and South America, widening the Atlantic Ocean. Subduction of several plates beneath North America’s western margin has nearly finished, and now most of North America is moving southeast relative to the Pacific Ocean. Relatively cold climates have prevailed on the earth for the past five million years, but the major glaciations of the Pleistocene Ice Ages began roughly 1.8 million years ago. During these glacial periods (only one of several episodes of glaciation in Earth’s history), ice sheets extended from their present positions on Antarctica, the Arctic Ocean, and Greenland over much of North America, Europe, Asia, and South America. North American Paleogeography: In North America, glaciers swept down from the north several times during the Quaternary, reaching south to states including New Jersey, Iowa, Montana, and extending as far south as present-day Kansas. As the glaciers moved south, they picked up sediment, gouging out features like the Great Lakes and Finger Lakes, and dropped it in different places, forming features like Long Island, Cape Cod, and many of the hills from Pennsylvania to South Dakota. Paleontology: The Quaternary has also seen the evolution and expansion of our own species, Homo sapiens. Quaternary fossils are often abundant, well preserved, and can be dated very precisely. Many paleontologists study Quaternary fossils, such as diatoms, foraminifera, and plant pollen in order to understand the climates of the past. The time since the melting of the last major ice sheet (about 11,000 years ago) is known as the Holocene, or Recent.

North America Today

While much of the continent is covered with a thin layer of Quaternary material, the areas shown on the map include large deposits found in the Great Valley of California, the basins of the Basin and Range Province in the western states, the Mississippi Delta, and along the Gulf and Atlantic Coasts. Also mapped are areas of recent volcanism including the Cascade Mountains, Snake River Plain, and around Yellowstone National Park.

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