Virgin Formation

The Virgin Formation is a special place in Utah where scientists 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 different from today. The Virgin Formation helps us learn about life 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 kinds of rock, such as 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 part of the Thaynes Group. The rocks formed in shallow ocean water near the shore. The lower part of the formation has repeating layers, while the upper part formed in lagoons in a dry climate to the southeast, with ocean deposits 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 learn about the early part of the Triassic time period.

History of investigation

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