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Title	Jurassic history and stratigraphy of Colorado
Publication Type	thesis
School or College	College of Social & Behavioral Science
Department	Geology
Author	Holmes, Clifford N.
Date	1960
Description	At the beginning of the Jurassic period western Colorado was a relatively low-lying, flat plain with the Ancestral Rockies reduced to low relief The Chino formation, on which the rocks of the Glen Canyon group rest, thins gradually from west to east and disappears completely before reaching the axes of the ancestral Uncompahgre and Colorado Range positive elements 0 The first rocks deposited, assigned to the Glen Canyon group, consist of the Wingate sandstone, Kayenta formation and Navajo sandstone, in ascending order. These formations were deposited in an immense desert basin. The Wingate sandstone pinches out rapidly within a belt that cuts diagonally across the western edge of the Uncompahgre high before reaching the axis of the positive element. No Wingate is known in or east of the central Colorado basin. The Kayenta formation has approximately the same distribution as the Wingate sandstone, but of flaps its outer boundaries. The Navajo and its equivalent the Nugget extend southeastward across northwestern Colorado into the central Colorado basin as far as Rifle Rocks of the San Rafael group are also present in Colorado although their marine origin is less evident here than in central Utah. The Carmel formation extends eastward only a few miles into Colorado before it disappears 0 The widespread Entrada sandstone transgresses all older formations before pinching out against the Ancestral Rockies in southwestern and north central Colorado In these areas the basal part of the Entrada contains fragments of igneous and metamorphic rocks where it rests on the Precambrian roc􁪽s of the positive elements. The Entrada is correlative with local units such as the Garo sandstone, Exeter sandstone, Dr. Bond sandstone, and the lower Stance The marine Curtis formation covers northwestern Colorado and extends southeastward in a fairly well-defined lobe as far as Aspen in the Central Basin Thin-bedded sandstone and shale beds that may correlate with the marine Curtis formation extend southward from Wyoming along the Front Range to the vicinity of Boulder. Th􁪽se have not yielded diagnostic fossils A gypsum deposit over 200 feet thick was formed in a restricted part of the Curtis sea, both to the southeast of the Colorado uplift and to the southwest of the Uncompahgre uplift In southwestern Colorado the gypsum deposit passes laterally into the Bilk Creek sandstone member of the Wanaka formation and the Moab tongue of the Entrada sandstone to the west. The Wanaka formation and the Tidily limestone are confined to the gypsum basin southwest of the Uncompahgre uplift The Wanaka formation passes laterally into the typical Summerville formation of western Colorado.
Type	Text
Publisher	University of Utah
Dissertation Name	Doctor of Philosophy
Language	eng
Rights Management	© Clifford No Holmes
Format	application/pdf
Format Medium	application/pdf
ARK	ark:/87278/s6d19tx4
Setname	ir_etd
ID	2206252
Reference URL	https://collections.lib.utah.edu/ark:/87278/s6d19tx4

Page Metadata

Title	Page 26
Format	application/pdf
Setname	ir_etd
ID	2206278
OCR Text	Show 11 GEOLOGIC HISTORY During early Paleozoic time, northeastern Colorado the, Transcontinental Arch; shallow, shelf-type posited in the Late karst nearly the -- at little effect in Peneplanation of the of the fonnation. followed of a sea Springs. prevailed An are at were raised These ranges trended north to north areas major Pennsylvanian uplift to and -- of the Transcontinental' apparently had the location of the Ancestral Rockies. The surface of the mild environment was a de was eldngate ranges and Wet early Paleozoic stable Uncompahgre Uplift, high angles covered by development the trend of the stable Phosphoria Glenwood as to controlling sion of the Permian far south vertically. after the three Uncompahgre, Colorado right angles Arch; the position stand at of erosion and Pennsylvanian time, (see Fig. 4), several thousand feet margin period This of part the limestone. on Ancestral Rockies west a was carbonate rocks during Mississippian time. Mississippian by topography In A thin sequence of sea. the state over the remainder of Colorado was an inva into the Central Colorado Basin overlap where is known highland along Mississippian overlapped by the ended with was beginning the as the western limestone beds gently dipping Cutler smoothed and a relatively of Mesozoic time. During the Triassic period, the basins to the west received occasional deposits of conglomerate with igneous and Uncompahgre complex exposed to metamorphic fragments the northeast, The derived from the lenticular, bedded sediments of the Cutler formation contrast with the cross strikingly reg ular, horizontally bedded, ripple-marked, fine-grained Moenkopi formation.
Reference URL	https://collections.lib.utah.edu/ark:/87278/s6d19tx4/2206278