Blackleaf Formation  search
BTChronostratigraphic Units
 .Phanerozoic
 ..Mesozoic
 ...Cretaceous
 ....Lower Cretaceous
 .....Blackleaf Formation
RTMontana
 Colorado Group
 Sweetgrass Arch
SNLower Cretaceous. NW and central Montana. In Colorado Group. Members ascending are Flood Member, Taft Hill Member, Vaughn Member, and Bootlegger Member. Underlies Marias River Shale; overlies Kootenay Formation. Added to Thesaurus in 1993.