Preliminary geologic map of the Rand quadrangle, North and Middle Parks, Jackson and Grand Counties, Colorado

Kinney, Douglas M.; Hail, W.J.

doi:10.3133/ofr70183

Cited by 1 publication

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“…In this formation, which may be as much as 3,000 m thick (Kinney, 1970), andesitic materials predominate in the lower part, and a fraction derived from Precambrian rocks increases upward. In the western part of the park, the very andesitic lower part of the formation is absent, and arkoses higher in the formation lie on an irregular surface cut over Precambrian and various Mesozoic rocks.…”

Section: North Park-middle Park Basinmentioning

confidence: 81%

“…In the western part of the park, the very andesitic lower part of the formation is absent, and arkoses higher in the formation lie on an irregular surface cut over Precambrian and various Mesozoic rocks. The basal andesite breccia and conglomerate member of the east side of the park is questionably of very Late Cretaceous age (Izett and others, 1962;Izett, 1968); the remainder of the formation is Paleocene and possibly early Eocene in age (Kinney, 1970).…”

Section: North Park-middle Park Basinmentioning

confidence: 99%

“…The Coalmont consists principally of conglomerates, arkosic sandstones, and mudstones or clay stones derived from Precambrian rocks; carbonaceous shales and some coal occur in the upper part (Hail, 1965). The formation does not contain the abundant andesite debris that characterizes the Middle Park Formation, but andesitic pebbles are present in a lower member in the southwestern part of the park (Hail, 1968) and in about the lower one-third of the formation in the southeastern part (Kinney, 1970). The Coalmont lies on a very uneven surface cut on Mesozoic and Precambrian rocks and contains a widespread unconformity between its middle and upper members.…”

Section: North Park-middle Park Basinmentioning

confidence: 99%

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Laramide (Late Cretaceous-Early Tertiary) Orogeny in the Southern Rocky Mountains

Tweto

1975

Geological Society of America Memoirs

141

130

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At the beginning of Laramide orogeny, a blanket of undisturbed Cretaceous and minor older Mesozoic sedimentary rocks 1,500 to 3,000 m thick covered the Southern Rocky Mountain province, and the last of a series of Cretaceous seas was starting to withdraw northeastward across the region. Beneath the blanket was an older and inhomogeneous terrane that in some places consisted of the eroded stumps of late Paleozoic mountain ranges made up of Precambrian rocks, and in other places of piles of sedimentary rocks thousands of meters thick on the sites of late Paleozoic basins. At the onset of Laramide orogeny in Late Cretaceous time, most of the buried mountain ranges were re-elevated, and adjoining Laramide basins, in part inherited from the late Paleozoic basins, began to subside and receive orogenic sediments. In addition, two anticlines of mountain-range proportions-the Sawatch and Uinta-rose from the sites of late Paleozoic basins.Orogeny began in the southwest part of the province before marine deposition ended in the northeast. The late Paleozoic San Luis highland of southwestern Colorado and northern New Mexico was re-elevated in late Campanian or middle Montana Cretaceous time, as indicated by orogenic sediments in the San Juan basin to the south and the Raton basin to the east. The Sawatch anticline, which diverges northward from the rejuvenated San Luis highland, rose at about the same time, as indicated by the age (72 to 70 m.y.) of fault-controlled porphyries on the flanks. The Front, Park-Sierra Madre, and Medicine Bow Ranges, on the site of the late Paleozoic Front Range highland, rose after the marine Fox Hills Sandstone was deposited over their sites 67.5 m.y. ago. Uplift and erosion were rapid. By 66 to 65 m.y., and before the close of Cretaceous time, 3,000 m of sedimentary rocks had been eroded from at least parts of these ranges, and streams were carrying detritus from Precambrian rocks to bordering basins.Once started, uplift of mountain units continued through Paleocene and into 1 on July 2, 2015 memoirs.gsapubs.org Downloaded from 2 O. TWETO Eocene time, as indicated by nearly continuous Upper Cretaceous to Eocene sedimentary sequences in the interiors of bordering basins. Uplifts grew laterally as they rose vertically. Consequently, the major uplifts of today are areally larger than those that supplied the first orogenic sediments, and their border structures are younger than those sediments. The crystalline rock body of the interior of the Laramide San Luis highland supplied sediments to adjoining basins in Cretaceous time, but the sedimentary rock flank of the uplift at the site of the Sangre de Cristo Range was not uplifted and deformed until Paleocene and early Eocene time. Similarly, an interior part of the Front Range supplied Precambrian rock detritus to bordering basins very late in Cretaceous time, but the flank structures of the range, which involve the early orogenic sediments, developed in Paleocene and Eocene time. The Laramie Range prong of the northern Front Range probably did not...

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Section: North Park-middle Park Basinmentioning

confidence: 81%

Section: North Park-middle Park Basinmentioning

confidence: 99%

Section: North Park-middle Park Basinmentioning

confidence: 99%

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