Elko Formation

The Elko Formation, also known as Elko Shale(s), is an oil shale geologic formation in Elko County, northern Nevada, United States. The deltaic and lacustrine shales and limestones preserve fossils dating back to the Middle Eocene of the Paleogene to Middle Miocene of the Neogene period. The frog genus Elkobatrachus and ant species Pseudocamponotus elkoanus were named after the formation.

Elko Formation
Stratigraphic range: Mid Eocene (Uintan)-Mid Miocene ~46.2–11.6 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Type	Formation
Sub-units	Elko Shale
Lithology
Primary	Shale
Other	Limestone
Location
Coordinates	40.8°N 115.8°W / 40.8; -115.8
Approximate paleocoordinates	41.5°N 112.9°W / 41.5; -112.9
Region	Nevada
Country	United States
Type section
Named for	Elko County
Elko Formation (the United States) Show map of the United States Elko Formation (Nevada) Show map of Nevada

Metasequoia occidentalis
Elko Formation

Description

The formation ranges in age from the Middle Eocene (Uintan), with the underlying lower member dated at 46.1 ± 0.1 Ma and the upper member of the Eocene section dated at 38.9 ± 0.3 Ma.^[1]

A younger section is dated to the Late Eocene to Early Oligocene (37.2 to 28.4 Ma)^[2] and the Elko Shale member is dated to the Middle Miocene (16.0 to 11.6 Ma).^[3]

Fossil content

The following fossils were reported from the formation:^[1][2][3]

• Elkobatrachus brocki
• Miopelodytes gilmorei
• Pseudocamponotus elkoanus
• Candona sp.
• Lymnaea sp.
• Sphaerium sp.
• ?Pontoniella sp.

See also

• List of fossiliferous stratigraphic units in Nevada
• Paleontology in Nevada
• Oil shale
• Middle Eocene Climatic Optimum
• Middle Miocene disruption