Rocks tell a story of upheavals

OREM — An earth sciences professor at Utah Valley State College — with the help of some of his students — has made a discovery in the Pequop Mountains of Nevada that reveals a new piece of the geological story of North America.

About eight years ago, researchers from Wyoming documented in the Pequops a foliation — a layering of rock caused during geological metamorphic events such as heating or pressure — that occurred when rocks slammed into each other about 80 million years ago.

UVSC professor Bill Dinklage and his students recently found a second foliation in the Pequops, located in northeastern Nevada between Wells, Nev., and Wendover, that appears to have occurred earlier than the first foliation.

Dinklage and students Victoria Sailer and Adam Healey wrote an abstract and presented their findings in May at a regional conference of the Geology Society of America at Mesa State College in Grand Junction, Colo.

At the time the foliations occurred, the Pequops — in the East Humboldt Range region — were part of a mountain belt called the Sevier orogeny that extended across Utah and Nevada. Mountain belts are large mountain groups — the Andes, Cascades and Wasatch are examples, Dinklage said.

"Many people have no idea how a continent can stretch. About 40 million years ago, Nevada was about half its size in an east-west direction," Dinklage said.

Throughout time, Pequop rocks moved and altered in composition. The Wyoming researchers found one foliation in an area that they determined resulted during a rock stretching period about 80 million years ago.

"I went in there skeptical it was so simple," Dinklage said.

In May 2004, Dinklage took a group of students to Nevada to look for a good geological research site. They settled on a 2-square-mile area of Pequops and returned in July for six days.

Other parts of the Sevier orogeny have been popular geological research sites, but the Pequops have rarely been studied, Dinklage said.

In July, they used a topographical map to delineate areas where different rocks were present — marble, schist, phyllite, quartzite — and marked boundary areas separating the rock types.

They gathered samples, returned to Orem and had the samples shaved into slices thinner than a strand of human hair. They needed thin slices for study under a microscope.

"The way light passes through them helps us identify them," Dinklage said.

By the fall, Dinklage and two students had looked at 38 of the samples using a microscope. They discovered the second foliation, which was less dominant than the first, when they noticed a line of tiny minerals embedded in the rock along one of the layers.