Elko Formation facts for kids

Quick facts for kids Elko Formation Stratigraphic range: Mid Eocene (Uintan)-Mid Miocene ~46.2–11.6Ma PreЄ Є O S D C P T J K Pg N
Type	Formation
Sub-units	Elko Shale
Lithology
Primary	Shale
Other	Limestone
Location
Coordinates	40°48′N 115°48′W / 40.8°N 115.8°W / 40.8; -115.8
Approximate paleocoordinates	41°30′N 112°54′W / 41.5°N 112.9°W / 41.5; -112.9
Region	Nevada
Country	United States
Type section
Named for	Elko County

The Elko Formation, also known as Elko Shale(s), is a special type of rock layer found in Elko County, in northern Nevada, United States. This formation is famous for being an oil shale deposit. This means it contains rocks that are rich in organic material. When heated, these rocks can produce oil.

The rocks in the Elko Formation were formed in ancient river deltas and lakes. They are mostly made of shale and limestone. These rocks hold amazing clues about the past, like fossils of plants and animals. These fossils tell us about life from the Middle Eocene part of the Paleogene Period, all the way to the Middle Miocene part of the Neogene Period. Some ancient creatures, like the frog Elkobatrachus and the ant Pseudocamponotus elkoanus, were even named after this important rock formation!

Discovering the Elko Formation

The Elko Formation is a significant geological formation in Nevada. It helps scientists understand Earth's history. Geologists study these rock layers to learn about ancient environments. They can also find out what kinds of plants and animals lived long ago.

What is a Geological Formation?

A geological formation is a specific set of rock layers. These layers have similar features, like their rock type or the fossils they contain. Geologists give them names to help map and study them. The Elko Formation is named after Elko County, where it is found.

How Old is the Elko Formation?

The rocks in the Elko Formation formed over a very long time. Scientists use special methods to figure out their age.

• The oldest parts of the formation are from the Middle Eocene Epoch. This time period is called the Uintan Age. These rocks are about 46.1 million years old.
• Other parts of the Eocene section are around 38.9 million years old.
• A younger part of the formation dates from the Late Eocene to the Early Oligocene Epoch. This means they are between 37.2 and 28.4 million years old.
• The youngest part, known as the Elko Shale member, is from the Middle Miocene Epoch. These rocks are about 16.0 to 11.6 million years old.

These different ages show that the Elko Formation was created over many millions of years. It records changes in the environment over this vast time.

What Fossils Are Found?

The Elko Formation is a treasure chest of fossils. These preserved remains give us a peek into ancient life. Scientists have found many interesting fossils here, including:

• Elkobatrachus brocki: This is an ancient type of frog. Its discovery helps us learn about frog evolution.
• Miopelodytes gilmorei: Another ancient frog species. It adds to our knowledge of prehistoric amphibians.
• Pseudocamponotus elkoanus: An ancient ant species. This fossil helps us understand the history of insects.
• Candona sp.: These are tiny freshwater crustaceans, like small shrimp. They lived in the ancient lakes.
• Lymnaea sp.: These are freshwater snails. Their shells are often found as fossils.
• Sphaerium sp.: These are small freshwater clams. They also lived in the ancient lake environments.
• ?Pontoniella sp.: This might be a type of crustacean, possibly related to modern shrimp.

These fossils help scientists reconstruct what the ancient environment of Elko County was like. They show that the area was once covered by lakes and rivers, supporting diverse life forms.