Anne Arundel County plans to purchase and preserve a prehistoric Indian site here that is rich in arrowheads, grinding stones and oyster shells, some dating to 4,000 B.C., county officials said last week.

The six-acre tract next to the Patuxent River and south of Annapolis is being sold to the county by sand and gravel pit operator J.E. Owens III for $135,000, said Joesph J. McCann, director of the county parks and recreation department.

"What makes this site unique is that the artifacts are as deep as six feet," McCann said, standing in the bristling morning wind on the site, once used for tobacco farming but now a barren field.

Owens was planning to mine the area for gravel but postponed it in 1981 at the county's request. He mines 100 adjacent acres.

Thomas Mayr, 73, a lifetime resident of Davidsonville and amateur archeologist who has been exploring the area for 50 years, said he had earlier alerted the Maryland Historical Trust that there were a number of layers of artifacts on the property. It is believed to have been the site of Indian villages for several thousand years.

Owens agreed to allow Wayne Clark, then an official with the Historical Trust, conduct an excavation in 1981 that yielded 6,000-year-old artifacts.

Clark, now director of Jefferson Patterson Park and Museum in Calvert County, said the site could settle questions about Indian habitation on the Western Shore.

"One of the big questions we haven't resolved yet is: When did Indians bring in corn and squash to the area? We think it was around 1,000 A.D.," he said. "This site could enable us to pinpoint that date."

Clark said archeologists do not know when Indians last lived there.

The site is one of about a dozen in the Chesapeake Bay region that contain artifacts of the Selby Bay culture, which existed between 200 and 800. Several of the scattered sites are known to contain artifacts that date to 10,000 B.C., said Richard B. Hughes, administrator of archeology for the Maryland Historical Trust.

Clark said the Selby Bay era is marked by items that were traded to other villages and brought by tribes hundreds of miles away. The soil, he said, contains traces of jasper from New York, mudstone from New Jersey, and rhyolite, a volcanic rock, rooted in the Frederick area.

Clark said he and three other archeologists involved in the excavation unearthed a small sampling of the artifacts. "About 99 percent remains intact," he said.

Many of the 300 to 400 tools, weapons and stones recovered from the land since 1981 are on loan to the State University of New York at Binghampton, where graduate students are examining them, Hughes said.

The age of the artifacts is being determined with carbon dating, a process scientists use to measure the charred remains. Burned organic materials, such as acorn nuts, "are essentially preserved and will not decompose," Hughes noted.

McCann said the county has signed a sales contract on the property and will pay the entire $135,000.

Meanwhile, county officials have told Owens, who sold the land for $95,000 less than its appraised value, that they will name the historic preservation area after him.

Hughes said the the Historical Trust has no immediate plans for excavation but expects to conduct digs eventually.

McCann said the recreation department plans to display artifacts and give occasional tours of the area. In the meantime, the location of the field is not being disclosed by officials, who want to prevent vandalism.