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Table 1. Generalized stratigraphic column of the Upper Colorado River Basin study unit
<br />[---, no data; Fm, formation; Ss, sandstone; Grp, group; Sh, shale; Ls, limestone. Parentheses indicate geologic units associated with the specific formation or
<br />group. Modified from Cashion, 1973; Pearl, 1974; Tweto, 1976; 1979; 1980; Tweto and others, 197R.J
<br />Map
<br />Period Epoch stratigraphic unit Principal lithology Thickness symbol
<br />(feet) used in
<br />figure 3
<br />Quaternary Holocene and Valley-fill deposits Clay, sand, gravel, boulders, and glacial 20-140 Not
<br />Pleistocene debris mapped
<br />Colluvium, landslide Silt, clay, sand, gravel, and debris piles 1(?-100 Not
<br />debris, glacial moraines, mapped
<br />Quaternary
<br />and Tertiary
<br />Tertiary
<br />Tertiary and
<br />Cretaceous
<br />Cretaceous
<br />terrace deposits
<br />Volcanic rocks
<br />Miocene and Browns Park Fm
<br />Oligocene
<br />Troublesome Fm
<br />Eocene Uinta Fm
<br />Green River Fm
<br />Eocene and Wasatch Fm
<br />Paleocene
<br />Paleocene and Middle Park Fm
<br />Late Cretaceous
<br /> Volcanic rocks of the
<br /> Laramide Orogeny
<br />Late Mesaverde Grp
<br /> (Price River Fm)
<br /> Mancos Sh
<br />Early
<br />Jurassic Late
<br />Middle
<br />Early
<br />Triassic Late
<br />Permian and
<br />Perutsylvanian
<br />Mississippian
<br />Devonian,
<br />Ordovician, and
<br />Cambrian
<br />Precambrian
<br />Pierre Sh
<br />Colorado Grp
<br />(Niobrara Fm and
<br />Benton Sh)
<br />Dakota Ss,
<br />Biuro Canyon Fm
<br />Morrison Fm
<br />(Brushy Basin Member)
<br />Eutrada Ss
<br />Glen Canyon Fm
<br />or Grp, Wingate Ss
<br />Chirtle Fm
<br />Maroon Fm, Belden Fm,
<br />Eagle Valley Fm
<br />Leadville Ls
<br />Mississippian rocks
<br />including Chaffee Grp
<br />and Manitou Fm
<br />Lava flows, breccias, tuff, and related --- QTuv
<br />materials
<br />Fine-grained grayish sandstone, gravel, As thick as I ,800 Tu
<br />cobbles, chert, fresh water limestone,
<br />and a conglomerate at the base
<br />Chiefly siltstone; contains beds of volcanic As thick as 1,500 Tu
<br />ash and some sandstone and conglomerate
<br />Sandstone and siltstone in the Piceance As thick as 1,000 Tl
<br />Basin
<br />Intertonguing lenses of siltstone, marlstone, As thick as 3,500 Tl
<br />sandstone, limestone, and shale
<br />Clay, shale, and lenses of sandstone, 300--5,000 Tl
<br />limestone, and conglomerate
<br />Sandstone, shale, conglomerate, and 2,SOt1-5,000 TKl
<br />breccia
<br />Intrusive rocks-mainly intermediate to --- TKv
<br />felsic in composition, some mafic
<br />Mudstone, shale, coal, and varicolored, 1,500-5,300 Ku 1
<br />crossbedded sandstone
<br />Dark shale and calcareous shale with As thick as 4,000 Kul
<br />interbedded sandstone
<br />Dark shale and sandy shale with local 200-4,000 Kul
<br />stringers of sandstone
<br />Calcareous shale and thin-bedded limestone 200-700 Kul
<br />interbedded with shale, dark fissile shale
<br />with bentonitic seams, and sandstone
<br />Light-colored sandstone, mostly cross- As thick as 300 Kl
<br />bedded, dark shale, and thin beds of coal
<br />Varicolored siltstone and mudstone with 25000 7
<br />beds of sandstone and limestone
<br />Fine-grained sandstone, mostly crossbedded 50-200 J
<br />Sandstone, lenses of limestone, varicolored As thick as 500 ~
<br />siltstone, and mudstone
<br />Red siltstone, sandstone, and limestone 80-120 ~
<br />Dolomite, limestone, quartzite, sandstone, As thick as 13,000 P1P
<br />conglomerate, shale, and chert
<br />Limestone, dolomite, sandstone, and chert 50-200 MDO
<br />Dolomite, limestone, and quartzite As thick as 2,500 MDO
<br />Granite, schist, gneiss, and pegmatite dikes --- p6
<br />ENVIRONMENTAL SETTING 5
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