Ascension Health Alliance, the parent organization of Ascension Health, announced an agreement today to acquire Tulsa, Okla.-based Marian Health System, which operates 36 hospitals and 150 clinics in the Midwest. Marian Health would continue to lead three regional health systems in Wisconsin, Minnesota, Oklahoma, and Kansas that would become part of Ascension Health, according to a spokesman for the Edmundson-based health system. "It's a merger. They will become part of Ascension Health," said Ascension Health spokesman Steve LeResche.