Lower Miocene and Upper Oligocene rocks or rocks equivalent to Upper and Lower Miocene rocks and White River Formation

Lower Miocene and Upper Oligocene rocks--Light-colored soft porous sandstone and underlying white tuffaceous claystone and siltstone. Arikaree Formation in Denver Basin; rocks equivalent to Upper and Lower Miocene rocks and White River Formation--Light-colored sandstone, white tuffaceous blocky claystone, and siltstone. Black Hills.
State Wyoming
Name Lower Miocene and Upper Oligocene rocks or rocks equivalent to Upper and Lower Miocene rocks and White River Formation
Geologic age Upper Oligocene-Upper Miocene
Lithologic constituents
Major
Sedimentary > Clastic > Mudstone > Claystone (Tuffaceous)
Sedimentary > Clastic > Siltstone
Sedimentary > Clastic > Sandstone
Minor
Sedimentary > Clastic > Conglomerate
Incidental
Igneous > Volcanic (Pyroclastic-tuff)
References
NGMDB product
Counties Albany - Converse - Crook - Goshen - Laramie - Niobrara - Platte