Geologic Unit: Madison

Usage:

Madison Limestone (CO*,ID*,MT*,NE*,SD*,UT*,WY*)
Madison Formation (CO*,MT*,ND,WY*)
Madison Group (ID*,MT*,ND*,SD*,WY*)

Subunits:

GROUP STATUS (alphabetical): Allan Mountain Formation (MT*), Castle Reef Dolostone (MT) or Castle Reef Formation (MT*), [?]Bottineau Formation (ND-outcrop), Charles Formation (MT*,ND*,SD*), Frobisher-Alida interval (informal) (ND-subsurface), Lodgepole Formation (ND) or Lodgepole Limestone (ID*,MT*,ND*,SD*,WY*), Mission Canyon Formation (ND) or Mission Canyon Limestone (ID*,MT*,ND*,SD*,WY*), Ratcliffe Formation (MT,ND).
FORMATION STATUS (alphabetical): Big Goose Member (MT*,WY*), Bottineau interval or Bottineau evaporite (informal) (ND-subsurface), Bull Ridge Member (MT*,WY*), Cottonwood Canyon Member (MT*,WY*), Little Bighorn Member (MT*,WY*), Little Tongue Member (MT*,WY*), Muddy Mountain Chert Member (WY), Paine Member (ID,MT,WY), Woodhurst Member (ID,MT*,UT,WY*).

Geologic age:

Early to Middle Mississippian (Tournaisian to Visean; Kinderhookian to Meramecian)*; locally, in southern MT, Late Devonian*

Type section, locality, area and/or origin of name:

Named from Madison Range, central part of Threeforks [Three Forks] quadrangle, MT, where it is conspicuously developed (US geologic names lexicons, USGS Bull. 896, 1200).
Type section (Madison Group): north side of Gallatin River, north of Logan, in SE/4 SW/4 sec. 25, T. 2 N., R. 2 E., Gallatin Co., MT (Sloss and Hamblin, 1942; Sando and Dutro, 1974).
Reference section: on north side of Gibson Reservoir, in SE/4 sec. 36, T. 22 N., R. 10 W., Patricks Basin quadrangle, Teton Co., MT (Mudge and others, 1962).

AAPG geologic province:

Bighorn basin*
Denver basin*
Great Basin province*
Green River basin*
Montana folded belt*
Piceance basin*
Powder River basin*
Sweetgrass arch*
Wasatch uplift*
Wind River basin*
Yellowstone province*