top of pageStratigraphy of the Dinosaur Ridge area
ERA PERIOD GEOLOGIC UNIT THICKNESS DESCRIPTION C
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yGreen Mountain Conglomerate
600 Boulder conglomerate with very poorly sorted sandstone and siltstone lenses Denver/Arapahoe Formation 1,200
Volcaniclastic sandstones and claystones, olive to light tan color. Very poorly sorted. Andesite pebble conglomerate near base and occasional granite and gneiss boulder beds above. Petrified wood fossils. M
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sLaramie Fm. 500
Gray, white, and tan fine- to medium-grained quartz sandstones and silty shales. Thin coal beds in lower part. Fossil palm tree fronds Fox Hills Fm. 60 Tan, friable, fine- to medium-grained quartz sandstone and gray shales. Occasional poorly sorted preserved leaf fossils Pierre Fm. 8,000 Gray shale with few thin sandstones. Ammonite fossils Niobrara Fm. 350 Dark gray calcareous shales with light gray fossiliferous limestone at base Benton Fm. 420 Dark gray shale with bentonite steaks. Thin limestones in middle part. Thin brown, sandy limestone with fossil shell "hash" and shark's teeth fossils at top. Fossil fish scales, bones, vertebrae, and ammonites in gray shales near base. D
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pSouth Platte Fm. 270 Light gray, fine- to medium-grained cross-bedded quartz sandstones. Several dark gray shales in middle part. Leaf and tree limb fossils, numerous trace fossils and rarely dinosaur foot tracks. Lytle Fm. 100 Light gray, fine- to coarse-grained, locally conglomeratic, cross-bedded quartz sandstone. Frequent gray and maroon shale lenses. Diagnostic chert pebbles in conglomerate. Base of formation by convention is the lower-most sandstone containing chert pebbles. Jurassic Morrison Fm. 350 Maroon and gray-green shales and buff quartz sandstones. Frequent thin limestones of fresh water lake origin. Famous for dinosaur bone fossils. Ralston Creek Fm. 100 Light red to tan shales, sandstones and thin gypsum beds. Triassic Lykins Fm. 120 Red mudstones with two thin, white marine limestones (Falcon & Glennon) in lower part. P
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CPermian Lyons Fm. 120 White to gray, fine- to medium-grained, well-sorted, cross-bedded quartz sandstone. Arkosic fine-pebble conglomerate lenses frequent. Paleo-mudcracks occur in several zones. Near Lyons, CO, paleo-raindrop impressions common. Pennsylvanian Fountain Fm. 1,000 Red, fine- to coarse-grained, poorly sorted, cross-bedded, arkosic quartz sandstone and coarse conglomerate. Thin red mudstones common. Well-cemented beds resistant to weathering and form ridges and "flat-irons". PRECAMBRIAN
Idaho Springs Fm.
Gneiss, schist, granite, granitic pegmatites, and rarely marble. Highly resistant to weathering, forms mountains.
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