Unalaska Formation
The Unalaska Formation is a Miocene Era geologic formation on Amaknak Island and Unalaska Island, in the Aleutian Islands archipelago of southwestern Alaska.[1]
| Unalaska Formation Stratigraphic range: Miocene Era, Neogene Period | |
|---|---|
 Outcrops near Dutch Harbor, Unalaska | |
| Type | Geologic formation |
| Overlies | Aleutian Ridge |
| Thickness | 900–10,000 metres (3,000–32,800 ft) |
| Location | |
| Region | Aleutian Islands, Alaska |
| Country | United States |
| Type section | |
| Named for | Unalaska Island |
It consists mainly of volcanic breccia, flows, tuff, and intercalated sedimentary rocks.[1] It is exposed over about 70 percent of Unalaska Island. The Dutch Harbor Member is a 126 metres (413 ft) thick Early Miocene sequence of the formation.[1]
It preserves fossils dating back to the Miocene era of the Neogene period.[2]
References
- USGS: Stratigraphy and depositional environment of the Dutch Harbor Member of the Unalaska Formation, Unalaska Island, Alaska
- Various Contributors to the Paleobiology Database. "Fossilworks: Gateway to the Paleobiology Database". Archived from the original on 31 July 2014. Retrieved 8 July 2014.
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