Hydrogeologic unit of Eisen et al. (1980) and Hydrogeologic unit of Gutentag and Weeks Hydrogeologic unit of Crist (1990) and Hydrogeologic role/unit of Hydrogeologic role/unit inferred from Hydrogeologic role/unit inferred from Hydrogeologic role/unit inferred from Western Water Consultants, Inc. (1982) (1980), Weeks and Gutentag (1981), Avery and Lithostratigraphic units of Love at al. Cooley and Crist (1981) Hydrogeologic unit of Libra et al. (1981) Statewide Framework Water Plan Hydrogeologic unit used in this report SYSTEM AND SERIES Rapp et al. (1957) Morris and Babcock (1960, Table I) Lowry and Crist (1967, Table I) [Flanks of Laramie Mountains, Pettijohn (1984), and Gutentag et al. (1984) (1993) in the Denver-Julesberg Basin [Laramie County, Wyo., and adjacent [Denver-Julesberg Basin, southeastern Wyo.] (WWC Engineering et al., 2007, Figure 4-9) for Denver-Julesberg Basin [Goshen County] [Platte County] [Laramie County] including eastern flank bordering [Parts of Colo., Kans., Nebr., N.Mex., Okla., ERATHEM part of Colo.] [All of Wyoming] Denver-Julesberg Basin] S.Dak., Tex., and Wyo.]

Holocene Quaternary QUATERNARY Alluvium and terrace deposits Local aquifers Local aquifers Local aquifers Local aquifers4 Local aquifers4 Major aquifer-Quaternary aquifers Major aquifer-alluvial and unconsolidated-deposit aquifers Pleistocene 4,5,6,7 4

Pliocene1 4 High Plains Ogallala Formation3 Not discussed Not discussed Aquifer Aquifer Aquifer Major aquifer Major aquifer–sandstone Ogallala aquifer High Plains Miocene aquifer system Arikaree Formation3 Aquifer Aquifer Aquifer Aquifer Aquifer aquifer system Major aquifer–sandstone Arikaree aquifer Aquifer system Conglomerate White River Group3 CENOZOIC TERTIARY White Aquitard with White River Oligocene River Brule Formation3 Aquifer/confining unit Aquifer/confining unit Aquifer/confining unit Aquifer Aquifer/ Aquifer/confining unit5 discontinuous major Aquitard with discontinuous Marginal aquifer major aquifers aquifer system Tertiary aquifer/confining unit Formation2,3 Lower part confining unit5,6 and minor aquifers 2,3 6 Aquitard with discontinuous Chadron Formation Confining unit with local aquifers minor aquifers 5 Eocene2 Brule aquifer/confining unit Chadron aquifer/ confining unit6,7 Paleocene1

Lance Formation Aquifer Aquifer Aquifer Minor aquifer–Lance aquifer Lance- Major aquifer–sandstone Lance aquifer Lance- Fox Hills Fox Hills Fox Hills Sandstone Potential aquifer Aquifer Aquifer Minor aquifer–Fox Hills aquifer aquifer Major aquifer–sandstone Fox Hills aquifer aquifer

Pierre Shale Major aquitard Pierre confining unit Upper Cretaceous Not discussed/not present in investigators’ study area Major aquitard with discontinuous Confining units. minor aquifers CRETACEOUS Niobrara Formation Hydrogeologic characteristics Muddy Sandstone (referred to as the Major aquitard Niobrara confining unit unknown at time of study “Newcastle Sandstone”) Carlile Shale Major aquitard Carlile confining unit

MESOZOIC can be considered an aquifer Greenhorn Formation Major aquitard Greenhorn confining unit Belle Fourche Shale Major aquitard Belle Fourche confining unit Mowry Shale Major aquitard ? Mowry-Thermopolis Muddy Sandstone Minor aquifer–Muddy Sandstone [Newcastle] aquifer Not discussed Muddy Sandstone aquifer confining unit Lower Thermopolis Shale Aquitard Major aquitard Cretaceous Inyan Fall River Formation Potential aquifer Potential aquifer Minor aquifer Minor aquifer–Inyan Kara [Cloverly] aquifer Inyan Kara aquifer Kara (referred to as the Cloverly Formation) (referred to as the Cloverly Formation) (assuming equivalent to Cloverly aquifer) Group Lakota Formation Upper Morrison Formation Confining unit Aquitard with discontinuous minor aquifers Minor aquifer Morrison aquifer and confining unit Jurassic JURASSIC Sundance Formation Potential aquifer Hydrogeologic characteristics unknown Minor aquifer Sundance aquifer Middle Jurassic JURASSIC (?) AND TRIASSIC (?) Upper Triassic Not discussed Not discussed TRIASSIC Lower Chugwater Formation of Darton (1908) Confining unit Aquitard with discontinuous minor aquifers Major aquitard Chugwater confining unit Triassic Not discussed/not present/not defined in investigators’ study area at time of study Hydrogeologic characteristics Forelle Limestone Major aquitard Hydrogeologic role/unit not defined for study area unknown at time of study Not discussed PERMIAN Satanka Shale Confining unit Major aquitard Satanka confining unit ? ?

Upper Aquifer Major aquifer Major aquifer–limestone Casper Formation Not present in Casper aquifer Pennsylvanian Major Major aquifer– Hartville Formation Aquifer Aquifer investigator’s Aquifer Hartville PENNSYLVANIAN Middle Fountain Not aquifer Major aquifer– limestone Pennsylvanian Formation study area Aquifer discussed limestone aquifer Lower Pennsylvanian

Upper Not discussed/not present/not defined Paleozoic aquifer Mississippian in investigators’ study area at time of study Paleozoic aquifer system PALEOZOIC MISSISSIPPIAN Lower Guernsey Formation Aquifer Minor aquifer Major aquifer–limestone Guernsey aquifer

Mississippian Paleozoic aquifer system Englewood Formation/Limestone Not discussed/not present/not defined Not discussed/not present/not defined Not defined in investigators’ study area at time of study Major aquifer–limestone Hydrogeologic role/unit not defined for study area Not defined at time of study in investigators’ study area at time of study in investigators’ study area at time of study Upper Fremont Canyon Sandstone Aquifer (defined as Deadwood Formation at time of studies) Major aquifer–limestone Fremont Canyon aquifer Devonian DEVONIAN1

Lower Devonian SILURIAN1 Upper Ordovician ORDOVICIAN1 Middle Ordovician Lower Ordovician Upper Cambrian CAMBRIAN1 Lower Cambrian

PRECAMBRIAN Precambrian rocks Confining unit with locally permeable zones Confining unit with locally permeable zones Confining unit Minor aquifer–Precambrian aquifer Major aquitard Precambrian basal confining unit

1Rocks of Pliocene, Paleocene, Silurian, Ordovician, and Cambrian age not present in Denver-Julesberg Basin. 5Brule Formation of White River Group considered an aquifer and part of High Plains aquifer system only where permeable (coarse-grained deposits or zones of secondary 2Historically, the Chadron Formation has been considered Oligocene in age (Love et al., 1993, and references therein). Revision of the Eocene-Oligocene boundary permeability) and in hydraulic connection with overlying Arikaree and Ogallala aquifers. Formation functions as lower confining unit to High Plains aquifer system where stratotype to about 34 million years before present or mega-annum (34 Ma) (for example, Berggren et al., 1992; Obradovich et al., 1995), and radiometric age-dating of impermeable. ash beds in the White River Group or Formation in Wyoming suggesting an age older than 34 Ma (Prothero and Swisher, 1992) infers the Chadron Formation is late Eocene 6Regionally, the U.S. Geological Survey does not consider the Chadron Formation to be part of the High Plains aquifer system, and the unit is classified as a confining unit in age (Swinehart and Diffendal, 1997). or confining unit with local aquifers underlying the High Plains aquifer system; however, regional U.S. Geological Survey potentiometric-surface maps of the aquifer system 3Relation of Tertiary lithostratigraphic units (Ogallala and Arikaree Formations and White River Group or Formation) to hydrogeologic units in southeastern Wyoming is include the formation where exposed at land surface in the Goshen Hole area in southeastern Wyoming (Gutentag and Weeks, 1980; Weeks and Gutentag, 1981; Avery and discussed in many additional studies not shown on this plate. See Figure 7-2 for summary of these studies. Pettijohn, 1984; Gutentag et al., 1984). 4Local aquifers in Quaternary unconsolidated deposits can be hydraulically connected laterally or vertically to underlying Tertiary aquifers of the High Plains aquifer system; 7Brule and (or) Chadron Formations (all or upper part) may be considered aquifers and in hydraulic connection with overlying Tertiary and Quaternary aquifers where where hydraulically connected, they are part of the aquifer system. Dashed line indicates possible hydraulic connection with underlying or overlying unit. permeable (coarse-grained deposits or zones of secondary permeability). Both formations function as lower confining unit(s) to overlying Tertiary and Quaternary aquifers where impermeable. Plate M. Relation of lithostratigraphic units to hydrogeologic units, Denver-Julesberg Basin.