This from Shadow Locked,
"Actress Susannah York, perhaps best known to fantasy fans as the mother of Superman in Richard Donner's 1978 take on the comic-book hero, has died of cancer at the age of 72. Nominated for a Best Supporting Actress Academy Award in the 1969 film They Shoot Horses, Don't They?, York perhaps made her deepest mark on British movies as the ingenue lover of Beryl Reid in Robert Aldrich's The Killing of Sister George (1968), thought by many to be the first film ever to seriously examine the subject of lesbianism.
Coming to early fame in 1963's Tom Jones, York was one of the most familiar faces of the 1970s and early 1980s, most especially in her unexpectedly extended role as 'Lara', mother of Superman-to-be Kal-El in the Christopher Reeve Superman cycle of movies between 1978 and 1987. In the theatrical release of 1980's Superman II, producers Alexander and Ilya Salkind balked at paying extra dues to include footage that Marlon Brando had shot for the second movie in the single block of filming that he did for the series in 1977, and instead re-engaged York to substitute his scenes as Superman's 'spiritual adviser' in the Fortress Of Solitude. The Brando footage was reinstated a few years ago in a specially released Richard Donner cut of Superman II, excising York's contributions."
So, another CBM legend gone. Rest in peace, Susannah.