Geologic units in Goshen county, Wyoming

Lower Miocene and Upper Oligocene rocks or rocks equivalent to Upper and Lower Miocene rocks and White River Formation (Upper Oligocene-Upper Miocene) at surface, covers 40 % of this area

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.

White River Formation - Brule Member (Oligocene) at surface, covers 14 % of this area

Pale-pink to white blocky tuffaceous claystone and lenticular sandstone. Locally includes the Upper Conglomerate Member (Twru).

White River Formation - Chadron Member (Oligocene) at surface, covers 12 % of this area

Light-gray to dark-red tuffaceous claystone, sandstone, and lenticular conglomerate.

Dune sand and loess (Pleistocene-Holocene) at surface, covers 9 % of this area

Includes active and dormant sand dunes. In northwestern Wyoming is chiefly loess (age 12,000-19,000 years).

Alluvium and Colluvium (Pleistocene-Holocene) at surface, covers 9 % of this area

Clay, silt, sand, and gravel in flood plains, fans, terraces, and slopes.

Lance Formation (Upper Cretaceous) at surface, covers 9 % of this area

(North Wyoming) - Thick-bedded buff sandstone and drab to green shale; thin conglomerate lenses. (South and Northeast Wyoming) - Brown and gray sandstone and shale; thin coal and carbonaceous shale beds.

White River Formation (Oligocene) at surface, covers 4 % of this area

White to pale-pink blocky tuffaceous claystone and lenticular arkosic conglomerate.

Gravel, pediment, and fan deposits (Pleistocene-Holocene) at surface, covers 0.8 % of this area

Mostly locally derived clasts. Includes some glacial deposits along east flank of Wind River Range. Locally includes some Tertiary gravels.

Hartville Formation (Lower Pennsylvanian-Permian) at surface, covers 0.7 % of this area

Red and white sandstone underlain by gray dolomite and limestone, red shale, and red and gray sandstone. Lowermost unit may be Late Mississippian in age.

Guernsey Formation (Upper Devonian-Lower Mississippian) at surface, covers 0.5 % of this area

Blue-gray massive cherty limestone and dolomite. Locally includes unnamed dolomite and sandstone of Devonian and Cambrian(?) age.

Upper Miocene Rocks (Upper Miocene) at surface, covers 0.5 % of this area

Southwest Wyoming: South end of Wind River Range--Siliceous, arkosic, and locally radioactive sandstone, claystone, and conglomerate. Fission-track age about 27 Ma. Recent work suggests that part of these deposits may be of Eocene age. Pliocene and Miocene (as originally defined 2) South Pass Formation. Saratoga Valley--White to greenish-gray tuffaceous sandstone, siltstone, and claystone; locally conglomeratic. North Park Formation; Central Wyoming: Arkosic sandstone, conglomerate, and siltstone; some light-colored tuffaceous radioactive claystone and white cherty limestone. North of Sweetwater River in Granite Mountains--Light-colored tuffaceous radioactive claystone, siltstone, sandstone, and arkose. Moonstone Formation; East Wyoming: Light-colored tuffaceous claystone, sandstone, and conglomerate. Ogallala Formation in Denver Basin.

Metasedimentary and metavolcanic rocks (Middle Archean-Late Archaen) at surface, covers 0.5 % of this area

Amphibolite, hornblende gneiss, biotite gneiss, quartzite, iron-formation, metaconglomerate, marble, and pelitic schist; locally preserved textures and structures suggest origin to be sedimentary or volcanic. Older than 2,875 Ma in Teton Range; older than 3,200 Ma in Granite Mountains; older than 2,600 Ma in Medicine Bow Mountains and Sierra Madre, where it is the Late Archean Phantom Lake Metamorphic Suite 3.

Granitic rocks of 1,700-Ma Age Group (Early Proterozoic) at surface, covers 0.2 % of this area

Granitic rocks of 1,700-Ma Group

Granitic rocks of 2,600-Ma Age Group (Late Archean) at surface, covers 0.1 % of this area

Teton Range--Mount Owen Quartz Monzonite. Age 2,500+/- Ma; may be of Early Proterozoic age. Gros Ventre and Washakie Ranges--Granitic rocks. Yellowstone National Park, Owl Creek, Granite, and Seminoe Mountains, Rawlins uplift, and Medicine Bow Mountains--Granite. Wind River Range--Granodiorite to porphyritic and equigranular granite. Sierra Madre--Granite and granodiorite. Laramie Mountains--Granite, amphibolite, and minor amounts of metasedimentary rocks. Hartville uplift--Granite and quartz monzonite. Black Hills uplift--Granite and minor amounts of metasedimentary rocks.

White River Formation - Upper conglomerate member (Oligocene) at surface, covers < 0.1 % of this area

Light-gray soft conglomeratic tuffaceous sandstone and conglomerate of Precambrian clasts.

Fox Hills Sandstone (Upper Cretaceous) at surface, covers < 0.1 % of this area

Light-colored sandstone and gray sandy shale containing marine fossils.

White River Group (Oligocene) at surface, covers < 0.1 % of this area

Clay, some claystone, silt and siltstone. Predominantly greenish gray and volcaniclastic. Other occurrences are greenish gray to white and bentonitic. Local channel sandstone at base. Aprox thickness 195 ft.

Arikaree Group (Miocene to Oligocene) at surface, covers < 0.1 % of this area

Consists mainly of gray, fine, loose to compact sand that has layers of hard, fine-grained dark-gray concretions which vary from few in to 15 in and often have tabular form. Includes a large amount of volcanic ash mixed in with the sand. Contains a number of channels filled with coarse conglomerate along ridge south of North Platte River. About 500 ft thick.

Playa lake and other lacustrine deposits (Pleistocene-Holocene) at surface, covers < 0.1 % of this area

Chiefly clay, silt, and fine sand. Includes travertine deposits.

Granitic rocks of 2,000-Ma Age Group (Early Proterozoic) at surface, covers < 0.1 % of this area

Medicine Bow Mountains--Gaps Intrusion 3 (granitic). Hartville uplift--Granite and quartz monzonite of Flattop Butte 6; age 2,150+/- Ma.

Fox Hills Formation (Late Cretaceous) at surface, covers < 0.1 % of this area

Consists of fossiliferous, gray, ferruginous and yellowish fine-grained sandstone, arenaceous clays and a few interbeds of gray to brown sandy shale and coal totaling 172 ft thick at that section. Estimated thickness 500 ft.

Ogallala Group or Formation (Miocene) at surface, covers < 0.1 % of this area

Silt, sand, sandstone, gravel and conglomerate. Predominantly interfingered fine- to coarse grained, poorly sorted, arkosic, fluvial deposits of light-gray, light-olive-gray, and grayish-green calcareous silt and sand, and locally poorly consolidated conglomerate, sandstone, and siltstone.

Quartz diorite (Early Proterozoic) at surface, covers < 0.1 % of this area

Sierra Madre--Encampment River Granodiorite 4; age 1,800 Ma. Medicine Bow Mountains--Keystone Quartz Diorite 5. Hartville uplift--Diorite of Twin Hills 6.