Virgin Formation

The Virgin Formation is a special place in Utah where scientists can find fossils. These fossils are very old, from a time called the Triassic period. The Triassic was a time long ago when the Earth looked very different from today. The Virgin Formation helps us learn about what life was like during the Spathian substage, a part of the Triassic period. Studying these fossils teaches us about the plants and animals that lived millions of years ago.

Description

The Virgin Formation is made of different types of rock, including gray to yellowish gray limestone and greenish yellow to reddish brown shale or siltstone. The limestone layers can be up to 20 feet thick, and the whole formation can reach up to 150 meters in thickness. About 30% of this formation is limestone.

This formation sits on top of the "lower red member" of the Moenkopi Group and is underneath the Shnabkaib Member of the Moenkopi Group. It is also now considered part of the Thaynes Group. The rocks were formed in shallow ocean water near the shore. The lower part of the formation shows layers that repeat, while the upper part was formed in lagoons in a dry climate to the southeast, with ocean deposits continuing farther north.

Fossils

The Virgin Formation has many old fossils from the ocean. These include crinoids, pelecypods, gastropods, worms, crustaceans, and a special type of ammonoid called Tirolites. These fossils help scientists understand the early part of the Triassic time period.

History of investigation

The Virgin Formation was first called the Virgin limestone member of the Moenkopi Formation in 1922 by Harvey Bassler and John Reeside. Later, in 1954, it was raised to formation rank by S.J. Poborski in southwestern Utah.