Palynostratigraphic study of the Bear Gulch Member of the Heath Formation, central Montana, indicates an Upper Mississippian age for the deposit corresponding to Carboniferous palynofloral zone TK (ammonoid zone E2b, Namurian A). The palynoflora contains a diverse spore assemblage, including the Mississippian index Tripartites vetustus. In addition, the Bear Gulch Member contains an abundant and diverse acritarch assemblage. The age assignment is consistent with age determinations from studies of the ammonoid, conodont, and bryozoan faunas.