The Chickaloon Formation is a geologic formation in Alaska. It preserves coal measures deposited in a high-latitude basins during the Paleocene–Eocene thermal maximum. It is an important record of high-latitude terrestrial ecosystems during a period of global warmth, providing evidence for how arctic vegetation and ecological interactions responded to elevated temperatures and atmospheric carbon dioxide levels.
The formation preserves a diverse fossil leaf assemblage derived from floodplain and crevasse splay environments within fluvial sediment processes. These plant fossils represent a forested ecosystem dominated by a variety of broadleaf trees and conifers, including Metasequoia, along with aquatic and wetland plants. Analysis of leaf characteristics suggests that the region experienced a much warmer and wetter climate than present-day Alaska, with warm-temperate conditions and high precipitation under early Eocene climates.
See also List of fossiliferous stratigraphic units in Alaska Paleontology in Alaska
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