Sovran Financial will acquire Commerce Union.

Sovran, a bank holding company based in Norfolk, Va., said it had a definitive agreement to merge with Nashville, Tenn.-based Commerce Union in a stock swap valued at more than $600 million. The merged company will be one of the largest banking concerns in the Southeast, combining Commerce’s assets of $3.9 billion with Sovran’s $15 billion. Sovran has 357 branches, mostly in northern Virginia and the Washington area. The deal is expected to close in late 1987.