The Marine Corps last month transferred Lt. Col. Oliver L. North out of the job of coordinating a year-long classified study on the future of the corps and gave him a position involving less sensitive information, according to informed sources.

The Navy reportedly has withdrawn the 24-hour security detail provided by the Naval Investigative Service (NIS) although the former National Security Council staff aide's personal protection has continued with privately funded guards, sources said.

These steps were taken, sources said, at about the time that the Defense Department received inquiries about North's status and his access to classified material from The Washington Post and congressional staff, sources said.

Immediately after North was fired from the White House staff last Nov. 25 and returned to Marine Corps supervision, the House Armed Services Committee staff was told that he would be given a noncontroversial job "in personnel" on the Marine commandant's staff, according to House sources. Instead, he was assigned to plans and operations.

Last summer, after his public testimony before the House and Senate committees investigating the Iran-contra scandal, North served as chief coordinator of "Marine 2018," a long-range plan looking at the corps' next 30 years, evaluating threats and capabilities and preparing the future roles and missions of the Marines, according to Marine sources that asked not to be identified.

North's deputy on the project was Lt. Col. Robert L. Earl, his deputy on the NSC staff. Earl also was taken off the project last month, sources said. A source at Marine Corps headquarters said yesterday that Earl recently had been transferred to the Marine Development Center at Quantico, Va.

Earl, contacted yesterday at a Quantico office, refused to comment.

A spokesman for the Marine Corps refused to discuss North's past or current duties saying, "It was not appropriate to comment on the specific assignment an individual worked on." The spokesman described "Marine 2018" as "an operations plan" and added, "Specific details are classified."

North was unavailable for comment. His attorney, Brendan V. Sullivan Jr., did not return telephone calls.

Dennis Dean Kirk, Earl's counsel before the investigating committees, also would not accept questions, according to a secretary at his office.

North is eligible to retire from the Marines May 1, after 20 years of service, and is expected to take that step, according to former colleagues.

The report of the Iran-contra committees, to be released Tuesday, is expected to be particularly tough on North for turning classified materials over to individuals who had no security clearances, destruction of classified records involved in the Iran-contra affair, and taking some top secret material home without authority.

Those documents were returned to the White House.

Earl also participated in the destruction of records and was aware that North's secretary, Fawn Hall, removed top secret material from the White House without authorization last November. That material was given to North who included it in the material he returned to the White House.

The staffs of the two Iran-contra committees were interested in pressing the Pentagon on North's current access to classified material, but the panels did not do so.

North's desire for personal security protection from the government became an issue raised during the Iran-contra hearings.

In the spring 1986, after North's name appeared on a list issued by terrorist Abu Nidal, Vice Adm. John M. Poindexter, who, as national security adviser to the president was North's boss, rejected North's request that the White House provide protection to him and his family.

Subsequently, retired Air Force major general Richard V. Secord, the man who ran the private aid network to the Nicaraguan contras initially organized by North and who later took part in secret arms sales to Iran, paid for the installation of a $16,000 security system at North's Great Falls house.

In April 1987, however, the NIS agreed to give the North family 24-hour protection after a new death threat, according to a Navy spokesman.