Tobin Worner was looking for a rock to skip on the surface of Bear Lake. Wendy Whitehead tugged at what she thought was the end of a rusty pipe sticking from the ground in Tooele.

Instead, both teenagers touched a world that was much different from today's Utah: the Ice Age of maybe 18,000 years ago.

It was a time of heavy precipitation. Lake Bonneville covered much of the region, mammoths plodded through the tall grass, ground sloths the size of elephants munched tree leaves and saber-tooth tigers hid waiting for prey.

The "pipe" was the end of one of a pair of horns of an extinct species of musk ox. The object Worner pulled from the mud of Bear Lake was a mammoth vertebra.

Precise casts made from the fossils discovered by Whitehead, now a junior at Tooele High School, and Worner, a sophomore at Riverton High School, are the centerpieces of a new teaching kit prepared by the Utah Geological Survey. The "Ice Age Kit" was unveiled Thursday at the survey's Utah Core Research Center, 240 N. Redwood Road.

Besides the fossil casts, the kits include copies of an ancient projectile point made by the Clovis culture, discovered in southwestern Wyoming; photographs of landforms that were shaped by glaciers; and Lake Bonneville, maps and illustrations.

So far, three of the kits are available for loans ranging from two weeks to one month. Teachers can give a $25 refundable deposit. The kits must be picked up at UGS offices and returned there.

The original fossils will be kept at the Utah Museum of Natural History, on the University of Utah campus. But the casts are exact replicas, down to snail shells that were stuck to the mammoth bone.

Jim Kirkland, the state paleontologist, presented each of the teens with casts made from the remains they found. He also gave a mammoth bone copy to Worner's science teacher, Todd Monson, who was instrumental in tracking down the fossil's identification and finding out what to do with the discovery.

"This is the way we like to see people collect fossils," Kirkland said, handing a cast of one of the horns to Whitehead.

Sandy Eldredge, the survey's education specialist, noted that the agency had other teaching kits available for educators to borrow. But before the Ice Age Kit, the most recent was produced about seven years ago.

Two University of Utah students were important in preparing the Ice Age project, she added: Holly Godsey Bennett, graduate student, and Anji Marx, who is also an intern with the UGS.

In addition, former state paleontologist Jim Madsen helped track down Ice Age casts and purchased some as a donation to the project, said Kirkland.