Ogallala Formation (TXPOMIo;0)

State	Texas
Name	Ogallala Formation
Geologic age	Phanerozoic \| Cenozoic \| Tertiary \| Pliocene Miocene
Original map label	PoMo
Comments	Sand, silt, clay, gravel, and caliche. Sand, fine to cs-grain quartz, silty in part, caliche nodules locally, cemented locally by calcite and by silica, locally crossbedded. Minor silt and clay with caliche nodules, sandy in places. Gravel present locally, pebbles and cobbles of quartz, quartzite, minor chert, igneous rock, metamorphic rock, limestone, clay balls in lower part, and abraded Gryphaea in intraformational channel deposits and in basal conglomerate. Caliche sandy, pisolitic, white, gray, pink comprises 4 or 5 beds up to 12 ft thick. Forms ledges and caprock. Max thickness 550 ft.
Primary rock type	sand
Secondary rock type	silt
Other rock types	clay or mud; gravel; carbonate
Lithologic constituents	Major Unconsolidated > Coarse-detrital > Sand (Bed) Minor Unconsolidated > Fine-detrital > Clay (Bed) Unconsolidated > Fine-detrital > Silt (Bed) Incidental Unconsolidated > Coarse-detrital > Gravel (Bed)
Unit references	Bureau of Economic Geology, 1969, Amarillo Sheet, Geologic Atlas of Texas, Bureau of Economic Geology, University of Texas at Austin, scale 1:250,000. Bureau of Economic Geology, 1970, Perryton Sheet, Geologic Atlas of Texas, Bureau of Economic Geology, University of Texas at Austin, scale 1:250,000.
Geographic coverage	Andrews - Armstrong - Bailey - Borden - Briscoe - Carson - Castro - Cochran - Coke - Collingsworth - Crosby - Dallam - Dawson - Deaf Smith - Dickens - Donley - Ector - Fisher - Floyd - Gaines - Garza - Glasscock - Gray - Hale - Hall - Hansford - Hartley - Hemphill - Hockley - Howard - Hutchinson - Kent - Lamb - Lipscomb - Lubbock - Lynn - Martin - Midland - Mitchell - Moore - Motley - Nolan - Ochiltree - Oldham - Parmer - Potter - Randall - Roberts - Scurry - Sherman - Sterling - Swisher - Terry - Tom Green - Wheeler - Winkler - Yoakum