Fruitland Formation

Named for town of Fruitland on the San Juan River, San Juan Co, NM in the San Juan basin. No type locality designated. Conformably overlies cliff-forming sandstone of the Pictured Cliffs sandstone. Conformably underlies gray sandy shale of the newly named Kirtland shale. Consists of sandstone, shale, and coal. Coal beds are lenticular and more persistent than the other lithologies. Coal occurs at base at most localities. Is irregularly bedded ranging changing facies laterally and vertically from sandy shale to shaly or clayey sandstone. Weathers into pillars, knobs, pyramids, and other shapes. Iron carbonate concretions commonly containing barite occur at many localities. Ranges from 192 to 292 ft thick in area. Cross section. History of nomenclature chart. Geologic map. Cretaceous age. Barnes, Harley, Baltz, E.H., Jr., and Hayes, P.T., 1954, Geology and fuel resources of the Red Mesa area, La Plata and Montezuma Counties, Colorado: U.S. Geological Survey Oil and Gas Investigations Map, OM-149, 1 sheet, scale 1:62,500 Fruitland formation. Described in Red Mesa area, La Plata and Montezuma Counties, Colorado, where it is 510 to 520 feet thick. Occurs as a series of low ridges and valleys on the gentle backslope of the Pictured Cliffs. Consists of gray to brown to olive, fine- to medium-grained, cross-laminated and cross-bedded sandstone; dark-gray to black carbonaceous shale; green feldspathic sandy silty shale; and coal. Deposited in brackish water in coastal plain swamps and in freshwater on floodplains. Underlies Kirtland shale. Gradationally overlies Pictured Cliffs sandstone; contact placed at base of first carbonaceous sandstone or shale. Age is Late Cretaceous. Report includes geologic map, columnar section. Source: US geologic names lexicon (USGS Bull. 1200, p. 1440); supplemental information from GNU records (USGS DDS-6; Denver GNULEX). Unconformably underlies the newly named Cimarron Ridge Formation on the northwest flank of the San Juan Mountains about 17 mi north of Ouray on Spur and Cimarron Ridges, on border between Ouray (San Juan Mountain province) and Gunnison (Paradox basin) Cos, CO. Age is Late Cretaceous. [Scott, G.R., O'Sullivan, R.B., and Weide, D.L., 1984, Geologic map of the Chaco Culture National Historical Park, northwestern New Mexico [includes chapter on archaeology by W.B. Gillespie]: U.S. Geological Survey Miscellaneous Investigations Series Map, I-1571, 1 sheet, scale 1:50,000]( Is Upper Cretaceous formation mapped in San Juan Co, NM (San Juan basin). Overlies Pictured Cliffs Sandstone (Upper Cretaceous); underlies Kirtland Shale (Upper Cretaceous). Is highly variable sequence of intercalated lenticular sandstone, siltstone, mudstone, carbonaceous shale, and coal. Siltstone and mudstone are dusky yellow to moderate brown. Mudstone units generally are 5-20 ft thick, but locally are as much as 50 ft thick. Contains layers of swelling clays. White to yellowish-gray, medium-grained, friable sandstone beds of this unit are lenticular, and most are less than 10 ft thick; locally they contain sideritic ironstone concretions as large as 4 ft maximum dimension. Forms picturesque badland topography. Local individual coal beds are more than 6.5 ft thick. Red clinker beds mark the outcrops of burned coal beds. Total thickness of unit is probably less than 295 ft. Molenaar, C.M., and Baird, J.K., 1989, North-south stratigraphic cross sections of Upper Cretaceous rocks, northern San Juan basin, southwestern Colorado: U.S. Geological Survey Miscellaneous Field Studies Map, MF-2068, 3 sheets, scale 1:633,600 For more information, please contact Nancy Stamm , Geologic Names Committee Secretary.