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]

See also

• Alaska portal
• Paleontology portal

• List of fossiliferous stratigraphic units in Alaska
• Paleontology in Alaska