Chignik Formation
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| Chignik Formation | |
|---|---|
| Stratigraphic range: Campanian to Maastrichtian | |
| Type | Formation |
| Underlies | Tolstoi Formation |
| Overlies | Pedmar Formation |
| Thickness | Up to 600 meters |
| Lithology | |
| Primary | Conglomerate, sandstone, shale |
| Other | Coal seams |
| Location | |
| Region | Alaska |
| Country | United States |
| Extent | Chignik and Herendeen Bays |
| Type section | |
| Named for | Chignik Bay |
| Named by | Wallace Atwood |
The Chignik Formation is a geologic formation in Alaska. It preserves fossils dating back to the late Cretaceous period. It unconformably overlies the Aptian-aged Pedmar Formation and is overlain unconformably by the late Paleocene-aged Tolstoi Formation.[1][2]
The Chignik formation contains large amounts of coal, which was noted by Wallace Atwood when he formally described the formation in 1911.[1] The depositional environment of the Chignik appears to have been a cyclical sequence of terrestrial tidal flats and offshore marine deposits, with alternating beds of shale and sandstone, with coarse conglomerates present as well.[2][3] Some of the sandstone layers are oil-stained.[2]
