Rierdon and Piper Formations

Rierdon Formation (Jr): Gray, locally fossiliferous limestone that may contain floating grains of quartz sand, interbedded with greenish gray limy shale. Lagoonal and marine shelf. Thickness as much as 105 m (344 ft). Piper Formation (Jp): Upper part: red mudstone and gypsum; middle part: gray shale, limestone, and dolomite; lower part: red mudstone and gypsum. Marine and restricted coastal evaporite basins. Thickness as much as 75 m (246 ft).
State Montana
Name Rierdon and Piper Formations
Geologic age Jurassic
Lithologic constituents
Major
Sedimentary > Clastic > Mudstone (Bed)
Sedimentary > Carbonate > Limestone (Bed)
Sedimentary > Chemical > Evaporite > Gypsum (Bed)
Minor
Sedimentary > Carbonate > Dolostone (Bed)
Sedimentary > Clastic > Mudstone > Shale (Bed)
References

Vuke, S.M., Porter, K.W., Lonn, J.D., and Lopez, D.A., 2007, Geologic Map of Montana - Compact Disc: Montana Bureau of Mines and Geology: Geologic Map 62-C, 73 p., 2 sheets, scale 1:500,000. This map was digitized in 2012 as a result of a contract between the U.S. Geological Survey and the Montana Bureau of Mines and Geology.

NGMDB product
Counties Fergus