Carmen E. Turner, a high-ranking Metro official, was appointed yesterday as an interim successor to Richard S. Page, the transit authority's outgoing general manager.

Turner, a former federal transportation official who is Metro's assistant general manager for administration, will be the first black woman to head a major U.S. transit system, according to an American Public Transit Association spokesman. She will take over as acting general manager Wednesday.

Metro officials made clear, however, that Turner is not under consideration as a permanent replacement for Page.

She was selected, officials said, because Metro's politically fragmented board of directors, which includes government officials from Washington, suburban Maryland and Northern Virginia, remained unable to reach agreement on a new general manager.

Page, who has headed the Metro system for four years, has resigned to become president of the Seattle-based Washington Roundtable, a group formed by Washington State businesses to study economic and social problems. He praised Turner yesterday as a "good choice."

Metro's policy-making board recently narrowed its search for a new general manager to five candidates. According to reliable sources, they included former D.C. City Council chairman Sterling Tucker, former Arlington County Board chairman Joseph S. Wholey, Amtrak Vice President M.L. Clark Tyler and two assistant Metro general managers, William A. Boleyn and Theodore G. Weigle.

It is unclear when the board will choose a permanent general manager. The board met privately yesterday to consider the issue and is scheduled to meet again next Thursday.

Tucker, Boleyn and Weigle appeared yesterday to have strong advocates within the board, but no candidate has proved acceptable to all six board members. "Everybody has their own candidate," one board member said.

Turner's temporary selection was announced by Prince George's County Council member Richard J. Castaldi, the Metro board's chairman. The board, he said, had agreed the interim manager "should not be a current candidate" for the permanent post.

Turner also said she expected the board to act "with dispatch" in appointing Page's permanent replacement. "I think we've got an exciting program. My objective is to keep that momentum going," said Turner, who joined Metro's staff in November 1977 after serving as a senior civil rights official in the U.S. Department of Transportation. Turner has headed a Metro office that oversees data processing, personnel, civil rights, purchasing and other administrative services.

While Turner is the first black woman to head a big-city transit system, the transit association spokesman said, at least 25 white women and many black men have held similar posts across the country in recent years.

Turner's selection followed the board's adoption of a $363 million budget, described as austere by officials, for the next fiscal year.

Metro also issued new ridership figures, described by Page as "encouraging." They indicated that the number of subway passengers increased in April despite a fare rise, while the number of bus riders decreased less than expected. Fare boosts usually lead to declines in ridership.