in northern Maine include dark-colored sandstone and slate of the Tomhegan Formation in the upper part of the Moose River Group (Boucot, 1961) in Piscataquis
Andre died in his sleep due to heart failure. It was concluded as a congestive heart failure by the doctors in Paris. Congestive heart failure is caused as a result of a pituitary tumor secreting excessive hormones. Also, AndrÃ© chose not to be treated his entire life.
According to Wikipedia, the real Hugh Glass died in an attack by the Arikara, along with two other hunters. The story of The Revenant is based on his life (supposedly he really did survive a mauling by a grizzly) but since it's a fictionalised movie and not a documentary, obviously there are more than a few changes made.