The Ranchester is interpreted as a shallow, off-shore marine facies characterized by periods ofrestricted e n v i r o n m e n t a l c o n d i t i o n s . It r e p r e s e n t s adiminution of the supply of clay and silt into the areaof deposition followed by deposition of regressive sanddeposits during Quadrant and Tensleep time

Manchester Limestone Member— The Ranchester isa poorly exposed, variable sequence of cherty dolomiteand limestone, red shale and siltstone, and sandstone thatranges from about 20 to 80 feet in thickness in the Beartooth Mountains.

Both its lower and upper boundariesare transitional

The dark shale and limestone facies that occursin the lower part of the member at sections 5 and 6 mayrepresent a local partly non-marine sediment

The Horseshoe Shale Member is interpreted as a shallow, off-shore, predominantly marine facies of the transgressing Amsden sea

Horseshoe Shale Member — This m e m b e r consistsprincipally of red siltstone and shale and discontinuousthin beds of fine-grained quartz sandstone. Thin beds ofvaricolored, argillaceous, fine-grained limestone occur atsome localities (sections 9, 13, and 14), and at others (sections 5 and 6), the sequence includes plant-bearing darklimestone and shale. The Horseshoe ranges from about40 to 125 feet in thickness in the Beartooth Mountains.Although fossils are extremely rare in the HorseshoeShale Member, conodonts of Chesterian age (identifiedby J. W. Huddle) were collected at four localities

Darwin Sandstone Member—The Darwin is a discontinuous unit that consists principally of unfossiliferous,fine- to medium-grained, ordinarily cross-bedded quartzsandstone. It includes some red siltstone and shale inthe lower half at the north end of the Beartooth Mountains(sections 13 and 14). As in central Wyoming, the Darwinis absent at many localities (sections 5, 6, and 10) or represented only as sandstone deposits in sinkholes or solution cavities below the top of the Madison (section 1).Where present (sections 9, 13, and 14), it is about 30 to50 feet thick