Hydrogeologic Geologic Period Phase Stratigraphic Unit Unit
Modern- Alluvium associated with present Alluvial Aquifers Quaternary Glaciation rivers
Neogene Extension San Juan volcanic field Volcanics Transition
San Jose - Blanco Basin Formations San Jose Aquifer
Paleogene
Animas-Nacamiento-Ojo Alamo Animas Aquifer Formations Laramide
Kirtland confining Kirtland Shale unit
Fruitland Formation Fruitland-Pictured Cliffs Aquifer Pictured Cliffs Sandstone
Lewis confining Lewis Shale unit
Cliff House Sandstone
Cretaceous Mesaverde Interior Menefee Formation Aquifer Seaway
Mesaverde Group
Point Lookout Sandstone
Mancos confining Mancos Shale unit
Regional Cretaceous Seaway shale- dominated formations form multiple hydrogeologic units, most are confining units Jurassic Mesozoic Multiple sedimentary units deposited in the stable continent interior may be present that may form aquifers Triassic Sandstones
Permian Ancestral Rocky Mountains event Colorado Plateaus marine and non-marine sedimentary Ancestral Regional and formations form multiple Rocky Paradox Basin Pennsylvanian hydrogeologic units in the Paradox Mountains hydrogeologic Basin and may be present, depending units on location
Mississippian Lower Paleozoic sedimentary Devonian formations that are dominantly Paleozoic limestone and dolomite form multiple Silurian Carbonates aquifers preserved in the Paradox Ordovician Basin may be present depending on location Cambrian
Crystalline rocks of igneous and Crystalline Precambrian Precambrian metamorphic origin in mountainous bedrock region Table 11b-02-04-01. San Juan Basin stratigraphic chart. San Juan Basin
Unit Thickness Hydrogeologic Geologic Period Phase Stratigraphic Unit Physical Characteristics Hydrologic Characteristics (ft) Unit
Modern- Alluvium associated with present rivers Alluvial Aquifers Quaternary Glaciation
Neogene Extension Basaltic, andesitic and rhyolitic volcanic flows, ash flow tuffs and clastic San Juan volcanic field Volcanics Mountainous region debris Transition Red, gray, and brown mudstone to sandy shale with beds of fine to San Jose - Blanco Basin Formations 1,000 San Jose Aquifer conglomeratic sandstone Paleogene Varicolored shale, with interbedded breccia, conglomerate, and light to Animas-Nacamiento-Ojo Alamo 500-2,700 rusty browntuffaceous sandstone; McDermott Member at base is Animas Aquifer Important source of water in areas southeast of Durango Formations Laramide predominately conglomeratic
Interbedded sandstone, olive to gray shale, and siltstone; Farmington Kirtland confining Kirtland Shale 1,500 Usable yields probably limited to Farmington Sandstone Member. Sandstone Member, is thick to massive and crossbedded unit
Target formation for coal mining and coal-bed methane development; Fruitland Formation 500 Interbedded gray, brown and olive sandstone, shale, and coal. typically poor quality water due to presence of coal Fruitland-Pictured Sandstone, light-olive-gray, to grayish-orange and orange, well-sorted, fine- Cliffs Aquifer Pictured Cliffs Sandstone 400 Not a significant aquifer in Colorado to medium-grained, medium- to thick-bedded, and cliff-forming
Lewis confining Lewis Shale 1,800 Shale unit
Gray calcareous marine sandstone, shaly sandstone, and silty shale; Cliff House Sandstone 50-350 Cretaceous crossbedded and massive in places
Interior Mesaverde Seaway Light-gray sandstone, siltstone, and shale with several interbedded coal Presence of coal beds often determines water quality; widely used Menefee Formation 400-1,000 Aquifer seams; thickness decreases to the north where it pinches out regional aquifer where water quality is acceptable
Mesaverde Group Light-gray to brown marine sandstone, massive and cliff-forming; contains Point Lookout Sandstone 350 interbedded siltstone and shale in the lower part
Dark-gray, silty and sandy marine shale; contains some interbedded Mancos confining Mancos Shale 1,900 sandstones and limestones. unit
Regional Cretaceous Seaway shale-dominated formations form multiple hydrogeologic units, most are confining units
Jurassic Mesozoic Multiple sedimentary units deposited in the stable continent interior may be present that may form aquifers Triassic Sandstones Permian Ancestral Ancestral Rocky Mountains event marine and non-marine sedimentary formations form multiple hydrogeologic units in the Colorado Plateaus Rocky Paradox Basin and may be present, depending on location Regional and Pennsylvanian Mountains Paradox Basin Mississippian hydrogeologic units Devonian Paleozoic Lower Paleozoic sedimentary formations that are dominantly limestone and dolomite form multiple aquifers preserved in the Silurian Carbonates Paradox Basin may be present depending on location Ordovician
Cambrian Crystalline Precambrian Precambrian Crystalline rocks of igneous and metamorphic origin in mountainous region bedrock Table 11b-02-04-01. San Juan Basin stratigraphic chart,detailed. Colorado Geological Survey ON-010 Colorado Groundwater Atlas. Sources: Steven and others (1974); Lipman and Hail (1975); Craigg and others (1990); Dam and others (1990); Kernodle and others (1990); Levings and others (1990); Levings and others (1990b); Thorn and others (1990); Kernodle (1996); Levings and others (1996); Raynolds and Hagadorn (2017)