 | This article relies on a single source. (May 2026) |
| Chickaloon Formation | |
|---|---|
| Stratigraphic range: Thanetian–Ypresian ~ | |
 Exposed shales, sandstones, and coal beds of the Chickaloon Formation at Coal Creek, Alaska | |
| Type | Formation |
| Unit of | Matanuska–Susitna basin sedimentary sequence |
| Sub-units | Informal coal-bearing and fluvial facies divisions |
| Underlies | (varies locally; younger Eocene units in Cook Inlet–Matanuska region) |
| Overlies | Mesozoic basement and/or Upper Cretaceous strata (locally unconformable) |
| Thickness | Several thousand meters (locally variable) |
| Lithology | |
| Primary | Sandstone, siltstone, shale, mudstone, conglomerate |
| Other | Coal |
| Location | |
| Region | Matanuska Valley, Alaska |
| Country | United States |
| Extent | Matanuska Valley and adjacent basins, south-central Alaska |
| Type section | |
| Named for | Chickaloon River area |
| Named by | Martin & Katz (1912) |
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.
