Mayor Marion Barry yesterday nominated Maurice T. Turner to be the new police chief of the District of Columbia, completing a transformation of the city's police force that will put it firmly in the hands of a young, bolder generation of blacks that mirrors the changes Barry brought to City Hall when he became mayor in 1979.

Turner, a 45-year-old native Washingtonian who began his career as a foot patrolman here, has for the past two years been assistant chief in charge of field operations -- the No. 2 job on the D.C. department. He will replace Chief Burtell M. Jefferson, 56, who plans to retire June 30.

The selection of Turner means that Barry will have man of his own choice, and much more in his own image, as chief of the 3,628-member police force that patrols the streets of the nation's capital.

Jefferson, the city's first black police chief, was appointed by Mayor Walter Washington in 1978 and shared with him a fondness for ceremony and an identification with the quiet, order churchgoing residents of the city's working-class, middle-income black neighborhoods. With his pencil-thin moustach, the neat part down the side of his short-cropped hair and the open Bible on his desk, Jefferson often looked the part of a church elder.

The occasionally gruff-spoken, burly Turner promises to be a more secular chief, just as Barry is a more secular mayor. Turner is Barry's contemporary -- the mayor is 45 -- and the contemporary of many of the other self-described "can-do" administrators Barry brought into the bureaucracy to clean up what he called the "bumbling and bungling" of the past.

Turner and Jefferson operated in similar styles during their respective tours of duty in charge of the Field Operations Bureau. But generally, Jefferson has been more of a by-the-book administrator who rigidly observed the chain of command within the department, adhered to established procedures and avoided the press.

Turner has a reputation as somewhat of an administrative maverick who has maintained closer relations with rank-and-file officers -- particularly many of the blacks he recruited during the department's rapid racial transformation a decade ago. He also has been more accessible to the news media.

In announcing Turner's nomination, Barry said he and City Administrator Elijah B. Rogers wanted ". . . someone whose single purpose would be to reduce and prevent crime . . . someone who relates to every segment, every constitutency of this community and who will bring together our war on crime . . . and, of course, someone who is tough but fair administrator."

Turner said his "first priority will be the reduction of crime, protection of life and property and the apprehension of criminals." He said he plans to expand foot patrols and crack down on narcotics as part of his strategy of combat the soaring crime rate in the District.

The changes that will accompany Turner's appointment underscore the transformation of the department's high command.

Turner, who served as the assistant chief for field operations under Jefferson, said Assistant Chief Marty Tapscott, 44, who during his early years on the force was labeled a militant because of his vocal opposition to discrimination, will take over the No. 2 position of field operations commander. Deputy Chief Theodore Carr, 44, will be promoted to assistant chief and wil become head of the administrative services office, Tapscott's former job.

Deputy Chief Isaac Fulwood, 40, a Jefferson confidante who heads the department's finance and management division, will be reassigned to command the 6th District in northeast, replacing Carr.

Charles E. Rinaldi, 51, assistant chief for technical services who is considered part of the old guard, was pointedly overlooked in the shuffle. Rinaldi campaigned actively for one of the department's top two jobs. But sources said his chances were damaged by disclosure of a letter on his behalf sent to the mayor by Sen. Alfonse D'Amato (R-N.Y.), chairman of the Senate D.C. Appropriations subcommittee.

Some observers considered the letter an untimely resurrection of efforts to assert Capitol Hill influence in city affairs, but Barry said yesterday that the letter had little weight on his decision.

The new line-up was announced at a press conference at police headquarters attended by the mayor's political aides from the District Building, several City Council members, community leaders and all the police department's top brass.

City Council member David A. Clarke (D-Ward One), head of the council's Judiciary Committee, said he expects to hold confirmation hearings on Turner June 3 and anticipates that Turner could be confirmed by the council by June 30.

Barry said Jefferson will remain in the department until June 30 to assist Turner in the transition period.

The mayor praised the chief, dressed uncharacteristically in a three-piece plaid suit, as one who "has carried on the department's proud tradition of professional excellence and of leadership among police departments in its progressive viewpoint and effectiveness. The chief has served the people of the District well."

Barry said there was no friction between him and Jefferson, as had often been reported. Sources have said that the two men differed over the size of the police force, with Barry believing that the force should be reduced and Jefferson maintaining that a larger force was needed to fight the District's crime rate, which inceased 13 per cent in 1980 over the prior year.

In naming Turner, Barry said he and the city administrator wanted a chief who would fight crime ". . . with the resources available to him, whether he believes them to be sufficient or not." Turner said yesterday he believes the 3,628 officers are enough to do the job.

When Turner takes over, he will be faced with a department whose morale has suffered in recent years. Last year, police officers were awarded a 5 percent raise, rather than the 9 percent they had sought. The city's budget has had to be cut, and the department has lost nearly 1,500 officers -- a 30 percent decrease -- since 1970.

Some officers have complained that the resources they now command are simply inadequate to have an impact on the crime problem. Some white officers have come to feel that their race limits their chances of promotion in the department, whose high command now includes nine blacks in the top 15 positions and whose overall composition is 45 percent black. The population of the city is 70 percent black.

Turner grew up in the 700 block of Girard Street NW, where he played football and basketball for the metropolitan police boys and girls club. His father was a payroll clerk in the old Department of Health, Education and Welfare. His mother still works as a clerk in the Office of Personnel Management.

He attended Monroe Elementary School and graduated from Dunbar High School in 1953. Six months later he joined the U.S. Marine Corps, where he served for three years.

On July 29, 1957, he joined the D.C. police force, where he started out as a foot patrolman. At the time, blacks were not allowed to ride in scout cars. Turner was promoted to sergeant in 1965, lieutenant in 1968, captain in 1971, inspector in 1974, deputy chief in 1976 and assistant chief in charge of administrative services in 1978.

During the tense days of Resurrection City in 1968, Turner was one of the few metropolitan police officers who could walk freely inside the tent city and talk to civil rights leaders. In 1977, he and Jefferson alternated 12-hour shifts where they maintained constant communication with the Hanafi Muslims as they held 124 captives at B'nai B'rith headquarters.

Divorced and the father of two daughters, Turner lives in the Gold Coast neighborhood of northwest Washington.

Tapscott, a native Washingtonian who is married and the father of two sons, is a graduate of Spingarn High School.