Chugwater Formation or Group

Chugwater Formation (North and Northeast Wyoming) - Red siltstone and shale. Alcova Limestone Member in upper middle part in north Wyoming. Thin gypsum partings near base in north and northeast Wyoming. Chugwater Group or Formation (South Wyomingt) - Red shale and siltstone containing thin gypsum partings near base. Group includes Popo Agie Formation (red shale and red, yellow, and purple siltstone; lenses of lime-pellet conglomerate), Crow Mountain Sandstone (red and gray, thick bedded), Alcova Limestone, and Red Peak Formation (red siltstone and shale). Chugwater Formation includes as members all the units listed above. Includes overlying Jelm Formation in Shirley and Seminoe Mountains and at northern end of Laramie Basin. Jelm Formation - Red sandstone.
State Wyoming
Name Chugwater Formation or Group
Geologic age Lower Triassic-Upper Triassic
Lithologic constituents
Major
Sedimentary > Clastic > Mudstone > Shale
Sedimentary > Clastic > Siltstone
Minor
Sedimentary > Clastic > Sandstone
Sedimentary > Carbonate > Limestone
Incidental
Sedimentary > Clastic > Conglomerate
References
NGMDB product
Counties Albany - Big Horn - Carbon - Converse - Fremont - Johnson - Natrona - Park - Platte - Washakie