CORYDON, Ind. (AP) — When a group of expert cavers crawled into a remote section of the Binkley Cave system beneath southern Harrison County in fall 2010, they discovered more than an uncharted cavern.
They found the remains of ancient visitors.
And the collection of well-preserved skeletons — including snakes, a black bear, owl and juvenile bison — constitutes "one of the largest and best preserved deposits of Ice Age bones yet discovered in Indiana," said Ron Richards, chief curator of science and technology at the Indiana State Museum in Indianapolis.
Black bears clawed at the walls, and peccary — a relative of the European pig — left visible tracks, which scientists say is rare.
The bones, which include teeth, legs, skulls and several nearly intact skeletons, jut from brown clay in dozens of locations, and are remarkably well-preserved. The remains have not been carbon-dated, but scientists estimate that they are at least 12,000 years old and possibly up to 50,000 years old.
"They have something really unusual," Missouri-based paleontologist Matt Forir, who has visited the cave, told The Courier-Journal in Louisville, Ky. (http://cjky.it/Zm6QgS ). "They have a cave full of bones that tell a really neat story."
Gary Roberson, the former co-owner of Marengo Cave, his wife Laura and two other partners are working to open part of the cave system — the 11th longest nationally — as Indiana Caverns and begin offering public tours in late May.
Both Forir and Richards made separate forays into the cave last summer at the owners' request, and both found evidence suggesting that various animals, including more than 100 peccary, wandered into the underground maze up to 15,000 years ago and got lost before an Ice Age closed the entrance.
In one location, animals navigated a passageway to a ledge and then evidently lost their footing and fell 30 feet to their deaths, Richards said. Other more sure-footed animals were able to climb down rocky outcroppings, and remains that were found elsewhere suggest that bears, peccary and smaller mammals reached a lower passage where a stream still runs through the cave.
Several bear beds, or wallows, have been identified, Roberson said.
What jumped out at Forir was the well-preserved condition of peccary in several locations, which is rare. "In the fossil record, you don't normally get fully articulated skeletons," said Forir, director of the Missouri Institute of Natural Science and a professor of speleology at Drury University in Springfield, Mo.
After a second trip to the cave last month, Richards estimated that Indiana Caverns ranks as one of the top peccary caves because there may be up to 200 skeletons represented. That's nationally significant, he said, adding that they may eventually find that "it's one of the better peccary caves anywhere."
Other "bone caves" feature mastodons and mammoths. Kentucky's Mammoth Cave, with its archaeological remains of prehistoric humans, isn't known for its animal bones, despite the discovery of remains of an extinct bat species, Richards said.
In Harrison, all bones are staying in the cave because scientists have cautioned that removing skeletons from the consistent temperature and humidity of the underground environment could do irreparable harm.
But Roberson said he and crews working to create safe walkways for cave tour visitors found that moving some bones has been unavoidable. In recent months, after drilling an entrance and preparing to pour concrete footers for an elevated walkway, they discovered loads of bones buried inches beneath the clay silt.
State and federal law doesn't protect paleontological finds in the same way as archaeological remains, so property owners are free to do what they want with such remains, Richards said.
Roberson said the owners intend to conserve the environment and avoid disturbing any bones unnecessarily, but he added that spending money on any research is taking a back seat to getting the business open.
Still, at cave experts' direction, they excavated around bones that were in the way and loaded them with large chunks of mud into plastic tubs that have remained inside the cave, Roberson said.
During a short trek into the cave on a recent morning, Roberson hiked back along a newly erected metal walkway into the dark reaches and returned — his headlamp shining — carrying a small plastic tub of bones.
The bones were caked with thick clay, but the shapes of teeth, ribs and leg bones were unmistakable.
Because the trove of bones holds "tremendous value in the interpretation of the Ice Age in Indiana," Richards said, he hopes that the state and the cave owners can collaborate to preserve the bone deposits for research and education. It could cost a minimum of $10,000 to pay a scientific team to conduct an extensive dig and have material radio-carbon dated.
Roberson said the owners hope to find grant money to help pay for scientific research at the site. He declined to disclose how much the partners are paying to develop the cave for touring.
"It's an unbelievable blessing to be the caretaker of something like this," said Carol Groves, Roberson's sister and the cave's new marketing director. "It's a privilege."
Richards said it would be ideal to map and assess all of the deposits, excavate for more remains and conduct radio carbon-dating.
He said there's tremendous potential for scientists to examine micro fauna, or minute bits of bats, mice, snakes, shrew and salamander, buried in the sediment because those animals exist today.
Because scientists know those animals' range and the environmental conditions they tolerate, the bones can offer clues about the conditions they survived during the Ice Age. That's not possible with extinct animals such as the peccary, Richards said.
Binkley Cave has been a popular destination for serious cavers for decades, but members of the Indiana Speleological Survey made a big breakthrough in early 2012 when they connected two known sections of the cave system, extending its length to 35 miles.
The explorations charted a clear path to a large room that the society named Big Bone Mountain, an area that also features a 50-foot waterfall. Because all of the entrances were on private property, Roberson — who helped develop nearby Squire Boone Caverns as well as Marengo Cave, which is in Crawford County — found three partners and bought 10 acres west of Ind. 135 to open the cave, which is four miles south of Corydon.
They drilled an entrance last summer to provide quicker access to Big Bone Mountain and have been working since to install lighting, walkways and a dam to allow for short underground boat rides.
An interpretive center is under construction now where visitors will be able to walk from a ground-floor room into the cave.
For Dave Everton, an avid caver from Bloomington and one of the first to venture onto Big Bone Mountain, knowing that scientists think the cave is nationally significant is amazing. "We've found bones in caves, but nothing like this. ... We were in the right place at the right time.
"A lot of us are really excited about this."
Information from: The Courier-Journal, http://www.courier-journal.com
This is an AP Member Exchange shared by the Courier-Journal.