A ruptured underground oil line at Quantico Marine Base spilled about 1,000 gallons of heavy home heating oil into the Potomac River over the week-end before the leak was discovered and repaired, a Marine Corps spokesman said yesterday.

The spill of No. 6 oil was confined to an area of the river near the base, which is 35 miles south of Washington, and base officials said the oil posed no threat to drinking water of or wildlife.

Marines began the cleanup operations Saturday afternoon using straw and garbage bags to contain, then retrieve the oil from both the Potomac and Chopawamsic Creek. The spill was discovered at 1 p.m. Saturday by an airline pilot who spotted the oil slick approaching National Airport.

Master Sgt. Bruce Martin, a Quantico spokesman, said marines, assisted by a Coast Guard boat and skimmer, had contained the spill into two areas about 100 yards from the shoreline of the base. Martin said the marines had collected more than 350 gallons of the oil by yesterday evening and that no more than 350 gallons went out into the main current of the Potomac River.

The weekend spill was the fourth such accident to occur at the Quantico base in 18 months, Martin said. Four weeks ago 2,000 gallons of No. 2 heating oil spilled into a creek flowing into Cedar Run Creek, which adjoins the base.