The Rockefeller Foundation announced Saturday that it had chosen Peter C. Goldmark Jr., a senior vice president of Times Mirror Co., as its new president and chief executive officer.

Goldmark, 47, will assume his new duties in July as head of one of the nation's oldest and most prestigious philanthropic organizations."This was an impossible challenge to turn down," said Goldmark, whose duties at Times Mirror included being in charge of the company's five Eastern newspapers. "Both the charter and the record of the Rockefeller Foundation are concerned with the largest questions of how we live together on this planet. This is a unique institution with a unique vantage point and experience at a moment of great promise for the future. It is an honor to be asked to lead it."

The selection of Goldmark to succeed Richard W. Lyman, the Rockefeller Foundation's president since 1980, came after a talent search during which almost 300 resumes were considered. Lyman, who will reach the foundation's mandatory retirement age of 65 in the fall, will return to Stanford University to head a new Institute of International Studies. He was president of Stanford for a decade until he joined the foundation.

"One of the things that was very important to the board was that Peter Goldmark saw global issues as the critical thing," said Dr. John R. Evans, head foundation trustee.

During his tenure, Lyman successfully completed some difficult tasks at the foundation, which was founded by John D. Rockefeller Sr..