Another archaeological site on the southern Oregon coast has been determined to be about 10,000 years old, making it the second-oldest known site in the state, according to Oregon State University researchers.

The site on a bluff just south of Bandon included a large number of stone flakes, charcoal pieces and fire-cracked rock, according to Roberta Hall, professor emeritus of anthropology at Oregon State and principal investigator in the study.

There also is evidence of a stone hearth, Hall added.

"There are a lot of rock outcrops nearby that would make good sources for tools," she said. "And it appears that tool-making is one of the activities the site may have been used for. So there is potential to find much more there."

The site was discovered after researchers analyzed a site in 2002 at Boardman State Park north of Brookings, which eventually was dated at nearly 12,000 years old, making it the oldest coastal archaeological site in Oregon.

Both sites are unusual, not only because of their age but in how they were discovered, Hall said.

The Oregon State research team developed a model using geologic features, soil type and radiocarbon dating to pinpoint locations most likely to include the oldest sediments.

Their theory was that the older sediments hold the greatest potential for finding sites from the late Pleistocene epoch — sites older than about 11,000 years — or sites from the early Holocene epoch, the scientific name given to the period covering the last 10,000 years.

The researchers hope the methods they have developed to locate and date the ancient sites will lead to the discovery of more and older sites.

Humans may have come to Oregon earlier than 12,000 years ago, the researchers say, but finding evidence of their habitation is extremely difficult.

Most archaeological sites are found with clues such as a projectile point or stone flakes. But the Oregon coast is a tough place to conduct archaeological research because of the weather, changing sea levels, and tumultuous geologic events, including earthquakes and tsunamis, researchers say.

In addition, the ocean was much lower in those ancient periods, Hall said, "meaning that any site that was on the coast during the late Pleistocene is now under water."

Results of their most recent study were published in the journal Radiocarbon.

The research team included Hall, geoarchaeologist and field work supervisor Loren Davis, graduate student Samuel Willis, and soil scientist Matthew Fillmore