The Cretaceous in Iowa, US

Cretaceous in Iowa map

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Cretaceous Fossils

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Paleontology and geology

The oldest Cretaceous rocks form the bedrock of northwestern Iowa and originated from sediments deposited in ancient river systems that drained westward to an interior seaway. Floodplains and coastal lowlands were covered with lush subtropical vegetation. Later in the Cretaceous, a vast shallow sea flooded eastward across the state, depositing layers of mud and limy sediments in western Iowa. Bones of large marine reptiles known as plesiosaurs have been found in these rocks. In southwestern Iowa, a fragment of fossil bone recovered from Cretaceous river deposits revealed a microscopic structure very similar to that seen in many dinosaur bones and may represent the first fossil dinosaur material found in the state.

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Databases (showing 1 of 1 listings)

Fossils in My Back Yard: Explore a geologic map of Iowa, county by county, to see lists and photos of fossils in the collections of the University of Iowa Paleontology Repository.

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General Reference (showing 1 of 1 listings)

The Age of Dinosaurs in Iowa: This page summarizes and illustrates dinosaur fossils found in the state of Iowa.

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