Robert O. Anderson, 90, whose two-decade tenure as chief executive officer of the Atlantic Richfield Co. included the discovery of North America's largest oil field, has died. Mr. Anderson died Sunday at home in Roswell, N.M., his family said.

He graduated from the University of Chicago in 1939 and went on to work for the American Mineral Spirits Co. He later purchased a small oil refinery in southeastern New Mexico and bought and expanded other refineries.

Mr. Anderson served as chief executive officer of ARCO for 17 years and was chairman of the board for 21 years. During his tenure, ARCO announced the discovery of oil at Prudhoe Bay in Alaska's North Slope in 1968.

He retired from ARCO in 1986 and formed Hondo Oil & Gas Co., serving as CEO until retiring in 1994.

Mr. Anderson sat on the board of regents at the New Mexico Institute of Mining and Technology from 1987 to 1992 and was named a distinguished professor in 1994.

The University of New Mexico named its business school in his honor.

- AP