Geologic units in Union county, New Mexico

Ogallala Formation (Lower Pliocene to middle Miocene) at surface, covers 30 % of this area

Alluvial and eolian deposits, and petrocalcic soils of the southern High Plains. Locally includes Qoa.

Upper and lower Cretaceous rocks of east-central and northeast New Mexico (Cenomanian and Albian) at surface, covers 22 % of this area

Consists of Dakota Group, which includes Romeroville Sandstone (Cenomanian), Pajarito Shale, and Mesa Rica Sandstone (Albian); the underlying Tucumcari Shale (Albian) in Tucumcari area and Glencairn Formation (Albian) in Union County.

Basaltic to andesitic lava flows (Pliocene) at surface, covers 16 % of this area

Includes minor vent deposits and small shield volcanoes. Flows are commonly interbedded in the Santa Fe and Gila Groups.

Morrison Formation and upper San Rafael Group (lowermost Cretaceous? - upper Jurassic) at surface, covers 7 % of this area

Morrison Formation and upper San Rafael Group

Eolian deposits (Holocene to middle Pleistocene) at surface, covers 7 % of this area

Eolian deposits.

Alluvium (Holocene to upper Pleistocene) at surface, covers 4 % of this area

Alluvium

Greenhorn Formation and Graneros Shale (Turonian and Cenomanian) at surface, covers 3 % of this area

Limited to northeastern area.

Chinle Group (Upper to middle Triassic) at surface, covers 3 % of this area

Map unit includes Moenkopi Formation (Middle Triassic) at base in many areas; in eastern part of state the following five formations are mapped: TRr, TRb, TRt, TRg, and TRs.

Morrison Formation (Upper Jurassic) at surface, covers 2 % of this area

Upper Jurassic nonmarine rocks.

Entrada Sandstone (Middle Jurassic) at surface, covers 1 % of this area

Entrada Sandstone

Landslide deposits and colluvium (Holocene to Pleistocene) at surface, covers 1 % of this area

Landslide deposits on western flanks of Socorro Mountains not shown for clarity.

Basaltic to andesitic lava flows (Holocene to middle Pleistocene) at surface, covers 1 % of this area

Flows south of Grants and west of Carrizozo are Holocene. Includes minor vent deposits.

Basaltic to andesitic lava flows (Miocene) at surface, covers 0.9 % of this area

Includes minor vent deposits. Flows are commonly interbedded in the Santa Fe and Gila Groups.

Intermediate to silicic volcanic rocks (Neogene) at surface, covers 0.6 % of this area

Mostly andesitic to dacitic strato volcanoes. Includes rhyolite lavas and tuffs in the Jemez Mountains, Volcanoes in Jemez Mountains and eastern Colfax County are upper Miocene. Mount Taylor and composite volcanoes in the Taos Plateau volcanic field are Pliocene.

Basaltic to andesitic lava flows (Neogene) at surface, covers 0.4 % of this area

Includes minor vent deposits. Flows are commonly interbedded in the Santa Fe and Gila Groups.

Basaltic to andesitic lava flows (Middle to lower Pleistocene) at surface, covers 0.1 % of this area

Includes vent deposits.

Carlile Shale (Turonian) at surface, covers 0.1 % of this area

Limited to northeastern area.

Ogallala Formation (Pliocene) at surface, covers < 0.1 % of this area

CIMARRON- Generally semiconsolidated clay, silt, sand, gravel, and caliche 0 to 400 feet thick. BEAVER- Interbedded sand, siltstone, clay, gravel lenses, and thin limestone. Caliche common near surface but occurrence is not limited to the surface. Caliche accounts for most of the white color in the Ogallala. Other colors generally light tan or buff but locally may be pastel shades of almost any color. The Laverne and Rexroad Formations of Pliocene age and the Meade Group and Odee (of local usage) and other formations of Pleistocene age occur locally and are included with the Ogallala Formation, 0-700 feet thick. WOODWARD- Gravel, sand, silt, clay, caliche, and limestone, locally cemented with calcium carbonate. Generally light-tan to gray to white. Thickness ranges up to 400 feet and probably averages 150 feet. CLINTON- Gray to light-brown, fine- to medium-grained sand with some, clay, silt, gravel, volcanic ash, and caliche beds; locally cemented by calcium carbonate. Thickness ranges from 0 to about 320 feet. The formation thins eastward.

Fort Hays Limestone Member of Niobrara Formation (Coniacian to Turonian) at surface, covers < 0.1 % of this area

Fort Hays Limestone Member of Niobrara Formation

Sand sheet deposits (Holocene) at surface, covers < 0.1 % of this area

Sand sheet deposits

Basaltic tephra and lavas near vents (Upper to middle Pleistocene) at surface, covers < 0.1 % of this area

Tuff rings, maars, cinder cones, and minor proximal lavas. Includes maars at Killbourne Hole and Zuni Salt Lake.

Dakota Sandstone (Early Cretaceous) at surface, covers < 0.1 % of this area

CIMARRON- Buff to light-brown, fine- to medium-grained, thin bedded to massive sandstone with interbedded shales.

Ogallala Formation (Pliocene to Miocene) at surface, covers < 0.1 % of this area

Ogallala Formation

Upper and Middle Jurassic rocks, undivided (Upper and Middle Jurassic) at surface, covers < 0.1 % of this area

In southwest includes the basalt-bearing Broken Jug Formation.

Dockum Group (Late Triassic) at surface, covers < 0.1 % of this area

CIMARRON- Upper shale unit: Varicolored siltstone or claystone, conglomerate, fine-grained sandstone, and limestone. Lower sandstone unit: Varicolored, fine- to coarse-grained sandstone with some clay and interbedded shale.

Dune sand sheet deposits (Holocene) at surface, covers < 0.1 % of this area

Dune sand sheet deposits

Caliche deposits (Pleistocene and Holocene) at surface, covers < 0.1 % of this area

Caliche deposits

Pierre Shale and Niobrara Formation (Campanian to Coniacian) at surface, covers < 0.1 % of this area

Pierre Shale and Niobrara Formation

Purgatoire Formation (Early Cretaceous) at surface, covers < 0.1 % of this area

CIMARRON- Kiowa Shale Member: Gray to black fossiliferous shale with sandstone in the upper part. Thickness ranges from 0 to 50 +/- feet. Cheyenne Sandstone Member: Massive, white to buff, fine- to medium-grained sandstone, containing some conglomerate in the lower part, from 0 to 120 +/- feet thick.

Alluvium (Holocene) at surface, covers < 0.1 % of this area

CIMARRON- Clay, silt, sand, and gravel 0 to 100 feet thick. TEXAS- Sand, silt, clay, and gravel located in valleys of principal streams. Thickness not known but may exceed 100 feet in North Canadian River valley and may be 50 to 100 feet in lower parts of valleys of Coldwater and Palo Duro Creeks BEAVER - Sand, gravel, silt, and clay in discontinuous lenses along courses of larger streams. 0-50 feet thick.

Niobrara Fm (Cretaceous) at surface, covers < 0.1 % of this area

Calcareous shale and limestone

Morrison Formation (Late Jurassic) at surface, covers < 0.1 % of this area

CIMARRON- Varicolored fine-grained sandstone, limestone, dolomite, shale, and conglomerate 0 to 470 +/- feet thick.

Exeter (Entrada) Sandstone (Late Jurassic) at surface, covers < 0.1 % of this area

CIMARRON- Massive, white to buff, fine- to medium-grained sandstone 0 to 50 +/- feet thick.

Terrace deposits (Pleistocene and Holocene) at surface, covers < 0.1 % of this area

Terrace deposits

Carlile Shale, Greenhorn Limestone, and Graneros Shale (Cretaceous) at surface, covers < 0.1 % of this area

Carlile Shale, Greenhorn Limestone, and Graneros Shale

Ogallala Fm (Tertiary) at surface, covers < 0.1 % of this area

Loose to well-cemented sand and gravel

Basalt (Pliocene) at surface, covers < 0.1 % of this area

CIMARRON- Dark, dense to vesicular volcanic rock 50 to 85 +/- feet thick forming cap rock of Black Mesa.

Alluvium (Holocene) at surface, covers < 0.1 % of this area

Alluvium