Stratigraphic relationships of the Eocene Duchesne River Formation and Oligocene Bishop Conglomerate, northeastern Utah—pulsed sedimentary response to rollback of the subducted Farallon slab (original) (raw)
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Late Cretaceous to Early Tertiary tectonostratigraphy of southwestern Utah
Museum of Northern Arizona Bulletin, v. 59, p. 181-188, 1993
The Upper Cretaceous to Paleogene sedimentary rocks of southwestern Utah record three temporally overlapping tectonic phases: 1) active Sevier-style thrust activity and foreland sedimentation; 2) cessation of thrust activity; and 3) active Laramide-style folding and intermontane sedimentation. The formations recording this tectonic evolution are, from oldest to youngest: the Iron Springs (and eastern equivalents), Kaiparowits, Canaan Peak, Grand Castle (new informal name), Pine Hollow, and Claron formations. Tbe Santonian to lower Campanian(?) upper part of the Iron Springs and mid-to-upper Campanian Kaiparowits formations represent synorogenic, fluvial sedimentation derived from the Sevier fold and thrust belt. The Iron Springs Formation received sediment from Precambrian to Upper Paleozoic strata exposed in the Wah Wah and Blue Mountain thrust sheets of southwestern Utah. The upper Campanian(?) to lower Paleocene Canaan Peak Formation was deposited in an east-to-northeast-directed, braided fluvial system. Petrographic and geochemical analysis of volcanic and siliceous clasts indicate that the Canaan Peak and Kaiparowits formations were derived from the Jurassic Deifonte Volcanics of southeastern California and the Mississippian Eleana Formation of southern Nevada. The early Paleocene Grand Castle formation represents an east- to southeast-flowing braided river system. Clast and sandstone lithologies indicate that the Grand Castle formation had the same provenance as the Iron Springs Formation. Conglomerate of the Grand Castle formation overlaps the easternmost Sevier thrust faults, suggesting a post-Sevier origin. The lower Pine Hollow Formation records active Laramide partition of the foreland basin associated with the development of the Johns Valley anticline and possibly the Circle Cliffs uplift. Fluvial, deltaic, and lacustrine deposits of the Claron Formation overlap paleotopographic highs of the Pine Hollow basin and indicate cessation of Laramide deformation by the middle Eocene.
Sedimentary Geology, 2001
The Neoproterozoic Uinta Mountain Group was deposited in an east-trending intracratonic rift bounded on the north by an active fault system and opening into a shallow sea on the west where the Big Cottonwood Group was deposited in an estuary. Although this rift may have been associated with the early stages in the breakup of Rodinia, it was not an aulacogen. Geochemical, Nd isotope, and detrital mode studies indicate that Uinta Mountain Group sediments were derived from mixed Archean and Paleoproterozoic sources with the former dominating. Big Cottonwood Group sediments appear to have been derived predominantly from Paleoproterozoic sources. The Archean sediment source is the Wyoming craton, and source rocks comprised dominantly granites enriched in Th, U, Y, Zr, Hf, and REE. The relative abundance of enriched granite implied by sedimentary rocks of the Uinta Mountain Group indicates that the Wyoming craton is anomalous compared to other Archean cratons. CIA values and A±CN±K relationships in shales of the Uinta Mountain and Big Cottonwood groups indicate high degrees of weathering of sources, probably in subtropical to tropical climates supporting a near-equatorial location for southwestern Laurentia at about 800 Ma. Differences in the Nd isotopic composition between the Big Cottonwood Group and Neoproterozoic sedimentary rocks in western Utah and northeast Nevada suggest a northwest-striking uplift in northwest Utah, possibly ancestral to the Paleozoic Toole±Uinta arch.
Faulty foundations: Early breakup of the southern Utah Cordilleran foreland basin
GSA Bulletin, 2021
Anomalous features of Upper Cretaceous strata in southern Utah challenge existing tectonic and depositional models of the Cordilleran foreland basin. Extreme thickness variations, net to gross changes, and facies distributions of nonmarine to marginal marine strata of the Turonian–early Campanian Straight Cliffs Formation are documented across the Southwestern High Plateaus. Contrary to most traditional models of foreland basin architecture, regional correlations demonstrate abrupt stepwise thickening, with a punctuated increase in average grain size of key intervals from west to east, i.e., proximal to distal relative to the fold-thrust belt. Except in the most proximal sections, fluvial drainage systems were oriented predominantly subparallel to the fold-thrust belt. Combined, these results suggest that modern plateau-bounding faults may have had topographic expressions as early as Cenomanian time, and influenced the position of the main axial river system by creating northeast-tr...
Kowallis, B.J., Christiansen, E.H., Balls, E., Heizler, M.T., and Sprinkel, D.A., 2005
Two ash beds from the Bishop Conglomerate along the south fl ank of the Uinta Mountains have given 40 Ar/ 39 Ar laser fusion eruption ages of 30.54 ± 0.22 Ma (ash of Diamond Mountain Plateau) and 34.03 ± 0.04 Ma (ash of Yampa Plateau).
Age determinations of non-marine sandstones and conglomerates generally rely on fossils and/or direct dating of volcanic ash. However, in fluvial deposits where air-fall tuff comprises a significant proportion of the sediment, U-Pb dating of detrital zircons can provide ages accurate to within 1 to 2 million years of depositional ages. This suggestion stems from several new U-Pb ages of detrital zircons acquired from a suite of conglomerate and sandstone samples from the Oligocene Bishop Conglomerate and Miocene Browns Park Formation in southwestern Wyoming and northwestern Colorado. The oldest maximum depositional U-Pb ages (MDA) for these samples are from Bishop Conglomerate outcrops in the southern Green River Basin (ca. 35-34 Ma). The Bishop is overlain by tuffaceous sandstone and siltstone that produced an MDA of ca. 33-31 Ma. In northwestern Colorado, Bishop Conglomerate is overlain by tuffaceous sandstone and siltstone of the Browns Park Formation with MDAs ranging from ~24-8 Ma. Collectively, the samples show consistently younger MDAs upsection. Tuffaceous components of Bishop Conglomerate and Browns Park deposits are air-fall ash derived from Basin and Range caldera complexes in southern Utah and Nevada. Radiometric ages of Basin and Range tuff units help constrain interpretations of Bishop and Browns Park MDAs. For example, the ca. 35-34 Ma MDA of the Bishop Conglomerate in Wyoming is consistent with the ~35.8 Ma tuff of the Stone Cabin Formation in the Basin and Range. However, zircon grains from the younger 31.7 Ma tuff of the Windows Butte Formation are absent from the 35-34 Ma Bishop Conglomerate sample, but are abundant in the overlying 33-31 Ma Bishop tuffaceous sandstone. In summary, we suggest that the MDAs from these deposits generally closely represent their depositional age. The quasi-continuous nature of Oligocene through Miocene caldera eruptions in the Basin and Range Province provided a continuous supply of air-fall ash that drifted across Utah, southern Wyoming and northern Colorado. Subsequent reworking of volcanic ash by rivers produced tuffaceous sandstones and conglomerates. These results suggest that other geologic periods characterized by quasi-continuous volcanic input, such as the Late Cretaceous of the western U.S., may permit similar dating of siliciclastic rocks.
2014
Cenomanian through Campanian strata of the Kaiparowits Basin in south-central Utah record the eastward migration of the Western Interior foredeep axis as the Sevier Thrust Belt approached from the west. Four, mostly conformable, depositional sequences were produced. With the exception of the lowest sequence, each is divided into four parts distinguishable on the basis of alluvial architecture. Together, the upper three sequences make up a nearly 2 km-thick succession comprised almost exclusively of fluvial deposits. At the base of each of these sequences are relatively thin, restricted sandstone sheets that grade both laterally and vertically into fine-grained deposits. Next are thick intervals of predominantly fine-grained material containing scattered lenses and thin sheets of sandstone. These intervals grade upward into extensive multistoried sandstone sheets that contain very little fine-grained material. Sequences are capped by laterally extensive multistory sheets of gravely s...
2017
Thin fallout tuffs in the Duchesne River Formation in the Uinta Basin, Utah are evidence that volcanism was active in northern Nevada and Utah in the late Eocene. The Uinta Basin is a sedimentary basin that formed during the Laramide orogeny. Ponded lakes of various salinity filled and emptied and during the late Eocene the northern rim was dominated by a wetland/floodplain depositional setting. Most of the tuffs have rhyolitic mineral assemblages including quartz, biotite, sanidine, and allanite. Rhyolitic glass shards were also found in one of the ash beds. Biotite compositions have Fe/(Fe+Mg) ratios typical of calc-alkaline igneous rocks and clusters of biotite compositions suggest 3 or 4 volcanic events. Sanidine compositions from five samples grouped at Or73 and Or79. Only one sample had plagioclase with compositions ranging between An22-An49. Some beds also contained accessory phases of titanite, apatite, and zircon. Whole rock compositions of the altered volcanic ash beds indicate these tuffs underwent post-emplacement argillic alteration, typical of a wetland/floodplain depositional setting. Immobile element ratios and abundances, such as Zr/Nb and Y are typical of a subduction zone tectonic setting and rhyolitic composition. 40 Ar/ 39 Ar ages constrain the timing of volcanism. One plagioclase and one sanidine separate from two different tuff beds yielded ages of 39.47 ± 0.16 Ma and 39.36± 0.15 Ma respectively. These dates, along with the compositional data seem to limit the eruptive source for these fallout tuffs to the northeast Nevada volcanic field. These new ages, along with previously published ages in the Bishop Conglomerate which unconformably overlies the Duchesne River Formation, constrain the timing of two uplift periods of the Uinta Mountains at 39 Ma and 34 Ma. Finally, the ages also date the fauna of the Duchesnean Land Mammal Age to be about 39.4 Ma as opposed to less precise earlier estimates that placed it between 42 and 33 Ma.
Lithosphere, 2010
Growth faults and synorogenic sedimentary strata preserved in Upper Cretaceous units on the margin of the Kaiparowits Basin in southern Utah pinpoint the timing of onset of the Laramide orogeny in this region between 80 and 76 Ma. The newly identifi ed listric normal faults, exposed in the steep limb of the East Kaibab monocline, sole into shales and evaporites of the Jurassic Carmel Formation. Faults lose displacement up-section through the Cretaceous Wahweap Formation and are associated with numerous coseismic sedimentary features. Fault orientations and slip vectors yield strain directions consistent with fold-related extension parallel to the axis of the growing East Kaibab monocline, or with development of a pull-apart basin at a bend in the trend of the fold. The association of the faults with the steep limb of a major basement-cored structure links them to initial Laramide movement along the Kaibab Uplift. When combined with recent radiometric ages of rock units bracketing the fault-induced growth strata, these sedimentary and structural features narrowly defi ne the onset of Laramide deformation in the western Colorado Plateau.
Detrital Zircon U-Pb Geochronological Provenance of Lower Cretaceous Deposits, Foreland Basin, Utah
U-Pb ages of detrital zircon (DZ) grains from Lower Cretaceous foreland basin quartzite conglomerate clasts and sandstones—and from potential sources of quartzite clasts and sandstones—record unroofing of the Sevier fold-thrust belt of Utah and the Mogollon Highlands of Arizona. The oldest Cretaceous deposits in Utah, the Buckhorn Conglomerate (Berremian-Aptian) of the Cedar Mountain Formation, contain sandstone and quartzite clasts with DZ age spectra statistically indistinguishable to Mississippian-Jurassic sandstones on the Colorado Plateau and in Sevier thrust sheets. Medial Albian Cedar Mountain Formation conglomerates on the western San Rafael Swell (Short Canyon Conglomerate) and basal Cedar Mountain conglomerates on the Wasatch Plateau in central Utah and the Markagunt Plateau in southwest Utah contain quartzite clasts derived from the Ordovician-Devonian interval in the thrust belt. Middle Albian-lower Cenomanian San Pitch and Sanpete Formations of the lower Indianola Group and upper Dakota Sandstone in central Utah were supplied with Cambrian-Precambrian quartzite clasts, thus recording full incision into approximately 16,000 m of allochthonous strata in the central Utah thrust belt by mid Albian. These three geochronological provenance intervals define three inverted chronofacies in Lower Cretaceous and basal Upper Cretaceous synorogenic deposits, thus recording a complete unroofing sequence of allochthonous strata in the central Utah thrust belt. The Buckhorn Conglomerate on the San Rafael Swell and the Poison Strip Sandstone in eastern Utah do not share a common provenance. The Poison Strip contains significant proportions of Cordilleran arc derived grains that are also commonly found in the lower Burro Canyon Formation to the southeast, whereas in the Buckhorn Conglomerate they are rare. Whether this phenomenon is due to temporal or sediment dispersal differences are unclear, it may signal the onset of longitudinal trunk river development subsequent to Buckhorn deposition and coeval with orogenesis. An additional source of Mesozoic volcanic arc DZ grains might include recycling from tephras within Mesozoic strata from local and southern sources in the Mogollon Highlands.
Middle Coniacian through Campanian deposits of the Kaiparowits Basin of south-central Utah record the migration of the foredeep basin axis as the Sevier Thrust Belt approached from the west. Three sequences were produced, each consisting of four parts that represent distinct styles of alluvial architecture and together make up a nearly 2 km-thick succession dominated by fluvial deposits. At the base of each sequence are laterally restricted sandstone sheets that grade both laterally and vertically into fine-grained deposits. Next are thick intervals of predominantly fine-grained material containing scattered lenses and thin sheets of sandstone. These intervals grade upward into extensive multistoried sandstone sheets that include very little fine-grained material. Sequences are capped by laterally-extensive multistory sheets of gravely sandstone and sandy conglomerate. Tectonic and eustatic models based on relationships between alluvial architecture and rates of accommodation space production were used to determine whether eustatic and tectonic effects can be differentiated from one another in a foredeep basin setting. Locally, both tectonically- and eustatically-controlled base level fluctuations appear to produce similar vertical patterns. The key to distinguishing between them seems to lie in regional distribution patterns for the coarse-grained sheets that cap each sequence. In tectonically-controlled sequences, these sheets tend to have planar lower and upper boundaries, become progressively thicker and coarser-grained upward through the section, thicken toward the thrust belt but are not traceable back to that region, and step in a progressively basinward direction. In eustatically-controlled sequences, sheets are essentially valley fill deposits with irregular lower boundaries, there is no overall vertical grain-size trend for successive sheets, and the sheets are traceable to the thrust belt. There may still be a progressive basinward migration of these deposits associated with the thrust belt advancement. Upper Cretaceous sequences of the Kaiparowits Basin most closely fit tectonic models, though significant eustatic effects are recorded in the lowest sequence.