Workers building a boat ramp at southeastern Indiana's Charlestown State Park have uncovered the apparent remains of a 4,000-year-old "kitchen" ancient American Indians tribes may have used to prepare their winter food supply.

The discovery of the site in eastern Clark County prompted the state to temporarily halt work on the Ohio River boat ramp project.

Bob McCullough, who heads an archaeological survey team from Indiana University-Purdue University Fort Wayne, said the low-lying area was probably used by nomadic tribes of hunters and gatherers.

He said they appear to have collected hickory nuts, used large slabs of rock to crush them and then made fires to boil them and extract fatty oils.

Tribes often stored such high-energy nut oils for use during the lean winter months, McCullough said.

The IPFW team has made two trips to the site and plans a third study of the area. The archaeological work is required under federal and state historic preservation laws.

No human remains or bones have been found at the site.

McCullough said he was surprised by how well-preserved the cooking area site was, but he said it was protected over the centuries by layers of silt deposited by floodwaters.

Michael Strezewski, the lead archaeologist from IPFW on the first two visits to the park last fall, estimated the site dates from about 2000 B.C. He said it contains large amounts of Laurel chert, a stone from which stone tools can be created.

Other artifacts included stone slabs used for grinding and cracking nuts, the remains of fire pits and some charred bits of plant material.

The area being studied is part of a 2,700-acre expansion at the park closed to the public. Over the years, several archaeological sites have been found in the park area.

Larry Gray, the park's property manager, said the $3 million project to install a five-lane boat ramp, a picnic area, parking lot and riverfront walking trail would probably be delayed until late this year or next year.

"I wish we were going to be prepared to open it in April or May this year, but we're not. We have to do things properly, and it takes time," he said.