Stratigraphy and Structure of the Uinta Range*
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Downloaded from gsabulletin.gsapubs.org on August 4, 2015 BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA VOL. 18, PP. 427-448, PLS. 43-48 NOVEMBER 30, 1907 STRATIGRAPHY AND STRUCTURE OF THE UINTA RANGE* BY F. B. WEEKS (.Presented by title before the Society December 29, 1906) CONTENTS Page Introduction ..................................................................................................................... 428 Geography ........................................................................................................................ 429 General features .................................................................................................... 429 Central a r e a ............................................................................................................ 430 Southern slope ........................................................................................................ 430 Northern slope.......................................................................................................... 430 Western end of the range.................................................................................... 431 Eastern end of the range...................................................................................... 431 Landslides and “rock streams” ....................................................................................431 Geology .............................................................................................................................. 432 General sections of Wasatch, Uinta, and Grand Canyon regions.............432 Geologic map .......................................................................................................... 432 General features .................................................................................................... 432 Pre-Cambrian “Uinta” formation....................................................................... 434 Nomenclature and correlation....................................................................434 Description ...................................................................................................... 435 Cambrian Lodore shales........................................................................................435 Nomenclature and correlation.................................................................... 435 Description ...................................................................................................... 436 Ordovician Ogden quartzite................................................................................ 436 Nomenclature and correlation.................................................................... 436 Description ...................................................................................................... 437 Carboniferous ......................................................................................................... 437 Mississippian s e r ie s ....................................................................................... 437 Nomenclature and correlation........................................................... 437 Description ............................................................................................. 438 Pennsylvanian series ...................................................................................438 Nomenclature and correlation................................................... •••• 438 Description .............................................................................................. 438 Weber formation .......................................................................... .. 438 Permian Permo-Carboniferous ..................................................................439 Nomenclature and correlation............................................................439 Description ..............................................................................................439 * Received by the Secretary of the Society from the censor September 13, 1907. * Manuscript received by the Secretary of the Society from the censor September 13, 1907. XXXVII— B u l l . G e o l . S o c . Am., Vol. 18, 1906 ( 427) Downloaded from gsabulletin.gsapubs.org on August 4, 2015 428 F. B. WEEKS— STRATIGRAPHY OF THE UNITA RANGE Page Post-Paleozoic ........................................................................................................ 439 Trias .................................................................................................................. 439 Jura ................................................................................................................... 440 Cretaceous ....................................................................................................... 440 Tertiary ........................................................................................................... 440 Interpretation of the sedimentary record............................................................... 441 Unconformities in the Uinta region...........................................................................441 Structure ........................................................................................................................... 442 In general .................................................................................................................442 General structural features of southern slope................................................ 443 General structural features of northern slope............................................... 443 Extent of major fold.............................................................................................. 444 Other similar folds................................................................................................. 445 Age of the folding................................................................................................... 445 Degradation ......................................................................................................................446 Geologic history ..............................................................................................................446 References ......................................................................................................................... 448 I ntroduction The geologic history of the Uinta region has been described by King and Emmons in the reports of the U. S. Geological Exploration of the Fortieth Parallel, and of the eastern portion by Powell in his Geology of the Uinta mountains. For more than 30 years these reports have com prised the extent of our knowledge of this interesting section. Recently Berkey published in the Proceedings of this Society an account of a reconnaissance in thè Duchesne region and discussed the bearing of his observations on the stratigraphy and structure. The 40th Parallel geologists had studied the ranges of northern Nevada and Utah, while Powell’s previous work had been in the Grand canyon of the Colorado and the plateau region of eastern Utah. The nomenclature and correlations of the two explorations varied considerably. Having taken part in several reconnaissance trips in Nevada and north ern, central, and western Utah in previous years, I was able during the summer of 1906 to extend this work over the Uinta range. About six weeks were devoted to this reconnaissance, which extended from the Wasatch mountains along the southern flank of the Uinta to the vicinity of Vernal, Utah; thence, crossing the range to the north, a side trip was made to Red creek, about 25 miles east of Green river ; thence, returning westward, it followed the north slope and around the western end to the Downloaded from gsabulletin.gsapubs.org on August 4, 2015 GENERAL GEOGRAPHIC FEATURES 4 2 9 starting point. The route of travel followed closely the strike of the Paleozoic strata. Geography GENERAL FEATURES The Uinta range as an orographic feature is a unit. It is a broad, anti clinal arch of horizontal or of slightly tilted strata 25 to 35 miles in width and 130 miles in length. The fold is not, however, wholly sym metrical, since there are regions of faulting and abrupt change to steep dips. It is limited on all sides by Tertiary strata, which abut against or overlap its slopes except on the west, where it is covered by lava flows Its culminating peaks and ridges extend in an east-west direction along the northern side of the broad summit of the arch. At the eastern end the fold is broad, but broken by sharply compressed folds and faults, while at the western end it narrows to a width of 10 to 12 miles. The plateau-like summit has been deeply dissected and eroded into jagged peaks and ridges having immense amphitheaters at their bases, widening out and then closing into deep glacial-cut canyons through the upturned Downloaded from gsabulletin.gsapubs.org on August 4, 2015 430 F. B. WEEKS----STRATIGRAPHY OF THE UNITA RANGE Paleozoic and Mesozoic beds which form the anticlinal slopes. Its aver age elevation is 9,000 to 11,000 feet and many peaks exceed 13,000 feet, the highest being Kings peak, 13,498 feet. CENTRAL AREA This region, varying from 10 miles in width on the west to 12 or 15 miles on the east, is formed of the horizontal strata of the “Uinta” forma tion more or less buried beneath debris not yet removed by erosion since the melting of the glaciers. Hundreds of lakelets and ponds, held in their rocky basins by accumulations of debris, still remain