Monday, October 25, 2010
Stone Talk - Turritella Fossil
Turritella 'Agate' is a chalcedony rich sedimentary rock from Wyoming which hosts the fossil shells of Elimia tenera was originally incorrectly called Turritella agate. It was named after the sea snail genus Turritella because of the resemblance of the freshwater snail shells to the Turritella fossils that are found in agate in Texas and California. The Wyoming fossil shells, however, are in a freshwater sedimentary deposit and identifiable as the genus Elimia which is an extinct species of freshwater snails. These fossilized and less-silicified Elimia tenera occur in a region which is now southern Wyoming, northern Colorado and northeastern Utah.
The fossil beds are approximately 46 to 51 million years old and occur in the Laney Member of the Green River Formation. Evidence suggests that the Elimia tenera were deposited nearshore in a series of shallow lakes, which geologists have named the Fossil, Uinta and Gosiute Lakes. The climate was subtropical and there were intermittent volcanic eruptions. The best preserved Elimia tenera are from Lake Gosiute which fossils occur in the Fort Laclede Bed of the Laney Member at outcrops in Sweetwater County, in southwestern Wyoming.
I find this stone fascinating. The one in the picture will be made into a pendant. During the past several years of my rock collecting I've realized that I'm very drawn to fossils. I think it's amazing that extinct species are preserved for future generations to study.
Ronnie is the jewelry designer at RadianTrace Jewelry. She's also the graphic artist at Mable's Makings, and the author of Ronnie Unplugged.