Geologic units in San Juan county, Utah

Additional scientific data in this geographic area

Cutler Group (Pennsylvanian to Early Permian) at surface, covers 24 % of this area

Cutler Group (White Rim Ss, De Chelly Ss, Organ Rock Shale, Cedar Mesa Ss, Halgaito Fm, and Elephant Canyon Fm). Includes Natural Bridges National Monument.

Glen Canyon Group (Early Jurassic) at surface, covers 17 % of this area

Glen Canyon Group (Navajo Ss, Kayenta Fm, and Wingate Ss). Includes Rainbow Bridge.

Eolian deposits (Quaternary) at surface, covers 16 % of this area

Eolian deposits

Morrison Formation (Brushy Basin and Salt Wash Members) (Late Jurassic) at surface, covers 11 % of this area

Morrison Formation (Brushy Basin and Salt Wash Members).

Dakota Ss and Cedar Mtn. or Burro Canyon Formations (Cretaceous) at surface, covers 7 % of this area

Dakota Ss and Cedar Mtn or Burro Canyon Formations.

Chinle Shale and Shinarump Conglomerate Member (Late Triassic) at surface, covers 5 % of this area

Chinle Shale and Shinarump Conglomerate Member.

Alluvium and colluvium (Quaternary) at surface, covers 4 % of this area

Alluvium and colluvium

Moenkopi Formation (Early Triassic) at surface, covers 4 % of this area

Moenkopi Formation.

Rico Formation (Pennsylvanian to Permian) at surface, covers 3 % of this area

Rico Formation.

Bluff Ss, Summerville Fm, Curtis Fm, Entrada Ss, and Carmel Formation (Middle to Late Jurassic) at surface, covers 3 % of this area

Bluff Ss, Summerville Fm, Curtis Fm, Entrada Ss, and Carmel Formation. Includes Arches National Park.

Landslides (Quaternary) at surface, covers 2 % of this area

Landslides

Older alluvial deposits (Quaternary) at surface, covers 1 % of this area

Older alluvial deposits

Hermosa Group and Molas Formation (Mississipian to Pennsylvanian) at surface, covers 0.9 % of this area

Hermosa Group (Honaker Trail Fm, Paradox Fm (oil, salt, potash), Pinkerton Trail Fm) and Molas Formation.

Mancos Shale (Late Cretaceous) at surface, covers 0.7 % of this area

Mancos Shale (Masuk Shale Mbr, Emery Sandstone Mbr, Blue Gate Shale Mbr, Ferron Sandstone Mbr, and Tununk Shale Mbr).

Laccolithic intrusions mostly diorite porphyry (Oligocene) at surface, covers 0.4 % of this area

Laccolithic intrusions mostly diorite porphyry (24-28 my).

Glacial deposits (Quaternary) at surface, covers 0.3 % of this area

Glacial deposits

Alluvial materials, Axtell and Harkers Formations (Pliocene to Quaternary) at surface, covers 0.2 % of this area

Alluvial materials, Axtell and Harkers Formations

Kaibab Limestone (Early Permian) at surface, covers < 0.1 % of this area

Kaibab Limestone.

Castle Valley Conglomerate (Pliocene) at surface, covers < 0.1 % of this area

Castle Valley Conglomerate.

Dakota Sandstone and Burro Canyon Fm (Cretaceous) at surface, covers < 0.1 % of this area

Sandstone, shale, and conglomerate. In northwest and west-central: Lower Cretaceous. In southwest: Lower and Upper Cretaceous.

Quaternary surficial deposits, undivided (Quaternary) at surface, covers < 0.1 % of this area

Unconsolidated to strongly consolidated alluvial and eolian deposits. This unit includes: coarse, poorly sorted alluvial fan and terrace deposits on middle and upper piedmonts and along large drainages; sand, silt and clay on alluvial plains and playas; and wind-blown sand deposits. (0-2 Ma)

Morrison Fm, Summerville Fm, and Entrada Sandstone (Jurassic) at surface, covers < 0.1 % of this area

Summerville Fm: Shale and siltstone

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

Commonly cliff-forming, cross-bedded sandstone lenses alternating with slope-forming siltstone, mudstone and shale. Colors are highly variable, and include greenish gray, reddish brown, pink, white, and purple. Sands were deposited by braided streams with finer sediment representing overbank or lacustrine deposits. (145-160 Ma)

San Rafael Group (Middle to Late Jurassic) at surface, covers < 0.1 % of this area

Commonly cross-bedded, ledge-forming sandstone and slope-forming siltstone. Rock typically has a striped red and white aspect. The Carmel Formation and Entrada Sandstone are prominent members of this group. (Late to Middle Jurassic, about 160-180 Ma)

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

Unconsolidated deposits associated with modern fluvial systems. This unit consists primarily of fine-grained, well-sorted sediment on alluvial plains, but also includes gravelly channel, terrace, and alluvial fan deposits on middle and upper piedmonts. (0-10 ka)

Eolian deposits (Quaternary) at surface, covers < 0.1 % of this area

Includes dune sand and silt and Peoria Loess

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

Variegated claystone, mudstone, sandstone, and local beds of limestone

Mancos Shale (Cretaceous) at surface, covers < 0.1 % of this area

In northwest and west-central: Intertongues complexly with units of overlying Mesaverde Group or Fm; lower part consists of a calcareous Niobrara equivalent and Frontier Sandstone and Mowry Shale Members; in areas where the Frontier and Mowry Members (Kmfm), or these and the Dakota Sandstone (Kfd) are distinguished, map unit (Km) consists of shale above Frontier Member. In Southwest: Lower part contains Juana Lopez Member (Kmj)

Landslide deposits (Quaternary) at surface, covers < 0.1 % of this area

Locally includes talus, rock-glacier, and thick colluvial deposits

Nugget Sandstone (Early Jurassic) at surface, covers < 0.1 % of this area

Nugget Sandstone.

Moenkopi Formation (Early and Middle(?) Triassic) at surface, covers < 0.1 % of this area

Dark red sandstone and mudstone; includes gypsum beds in northwestern Arizona; deposited on a low-relief coastal plain. (230-245 Ma)

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

Upper Jurassic nonmarine rocks.