Shinarump Conglomerate Research Articles

Evaluation of Rockfall-hazard Potential For Rockville, Utah, Following a 2013 Fatal Rockfall

Abstract In December 2013, a rockfall in the town of Rockville, Utah, released an estimated 2,700 tons (2,450 tonnes) of rock from a 400-ft (122-m) high slope; the rock struck a house at the base of the slope, resulting in two fatalities. We performed detailed field and laboratory investigations to (1) identify the modes of failure and factors contributing to rockfalls along the east-west trending, south-facing slope where it passes through the town; (2) identify sections of the slope that pose the highest hazard for future property damage or injury; and (3) suggest potential remedial measures. Field investigations included mapping discontinuities, establishing stratigraphy, measuring slope geometry, and evaluating potential failure modes at four selected sites. Laboratory investigations included determining dry density, friction angle, and slake durability index of rock samples. Using the Dips software, we determined the principal joint sets and performed a kinematic analysis. The maximum rollout distances for rock blocks of various sizes were determined for each of the study sites using the RocFall software. Results of the kinematic analysis and field observations indicate that wedge, plane, and toppling failures are possible within the Shinarump Conglomerate Member of the Chinle Formation and the Upper Red Member of the Moenkopi Formation along the entire slope. Based on the results of the study, we developed a rockfall-hazard map that indicates that the western portion of the town faces the highest hazard from potential rockfalls. The most feasible future remedial measure is not to build close to the hazardous slopes. Other possible remedial measures include removing loose rock blocks, installing rock anchors, and using drapery mesh.

Sources of volcanic detritus in the basal Chinle Formation, southwestern Laurentia, and implications for the Early Mesozoic magmatic arc

The Upper Triassic Chinle Formation in southwestern Laurentia is the oldest distinctive record of Early Mesozoic Cordilleran arc magmatism, in the form of detrital zircons and volcanic clasts. Initial deposition of the basal Shinarump and Mesa Redondo members, herein collectively called the Shinarump conglomerate, began in Late Triassic time, yet the earliest known arc magmatism is older by as much as 40 m.y. Analysis of detrital zircons from eight sites in southeastern Nevada, southern Utah, and northeastern Arizona and volcanic-clast zircons from four of these sites provides a basis for understanding the evolution of the Early Mesozoic arc. Most Permian and Triassic detrital zircons from the Shinarump conglomerate have ages from ca. 260 to 220 Ma with rare grains as old as 280 Ma. These ages are compatible with derivation from sources in the magmatic arc to the west and southwest, including plutons of corresponding age in the Mojave Desert. Volcanic clasts are uniformly in the range 232–224 Ma; their age and zircon geochemistry argue against a source in currently exposed Mojave Desert Triassic plutons. As a further test, we compared Th/U ratios of clast and detrital zircons with those of possible sources to the west. Th/U values of many detrital grains support their derivation from Triassic Mojave Desert plutons. Some detrital grains and those from the clasts, however, have Th/U values that are uniformly higher than those in Permo-Triassic Mojave Desert plutons and therefore argue for a different, unexposed source. We propose that the early arc lay offshore of western Laurentia. Over time, plutons were emplaced across a range of continental crustal thicknesses that likely increased toward the east. At approximately 235–230 Ma, a land connection between the arc and retro-arc areas was established and fluvial sedimentation began. The observation that the youngest grain ages in our detrital samples are variable suggests that this land connection was tenuous for perhaps 10 m.y. until well into Chinle Formation sedimentation.

Post-Paleozoic alluvial gravel transport as evidence of continental tilting in the U.S. Cordillera

Research Article| September 01, 2003 Post-Paleozoic alluvial gravel transport as evidence of continental tilting in the U.S. Cordillera Paul L. Heller; Paul L. Heller 1Department of Geology and Geophysics, University of Wyoming, Laramie, Wyoming 82071, USA Search for other works by this author on: GSW Google Scholar Kenneth Dueker; Kenneth Dueker 1Department of Geology and Geophysics, University of Wyoming, Laramie, Wyoming 82071, USA Search for other works by this author on: GSW Google Scholar Margaret E. McMillan Margaret E. McMillan 1Department of Geology and Geophysics, University of Wyoming, Laramie, Wyoming 82071, USA Search for other works by this author on: GSW Google Scholar Author and Article Information Paul L. Heller 1Department of Geology and Geophysics, University of Wyoming, Laramie, Wyoming 82071, USA Kenneth Dueker 1Department of Geology and Geophysics, University of Wyoming, Laramie, Wyoming 82071, USA Margaret E. McMillan 1Department of Geology and Geophysics, University of Wyoming, Laramie, Wyoming 82071, USA Publisher: Geological Society of America Received: 20 Jul 2002 Revision Received: 24 Feb 2003 Accepted: 18 Mar 2003 First Online: 02 Mar 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (2003) 115 (9): 1122–1132. https://doi.org/10.1130/B25219.1 Article history Received: 20 Jul 2002 Revision Received: 24 Feb 2003 Accepted: 18 Mar 2003 First Online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Paul L. Heller, Kenneth Dueker, Margaret E. McMillan; Post-Paleozoic alluvial gravel transport as evidence of continental tilting in the U.S. Cordillera. GSA Bulletin 2003;; 115 (9): 1122–1132. doi: https://doi.org/10.1130/B25219.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract The western United States contains three thin but remarkably widespread alluvial conglomeratic units that record episodes of large-scale tilting across the U.S. Cordilleran orogen in post-Paleozoic time. These units are: (1) the Shinarump Conglomerate of Late Triassic age exposed in northern Arizona and adjacent parts of Utah, Nevada, and New Mexico; (2) Lower Cretaceous gravel deposits that overlie the Morrison Formation throughout the Rocky Mountain region; and (3) the gravel-rich parts of the Miocene-Pliocene age Ogallala Group in western Nebraska and adjacent southeastern Wyoming. Paleoslopes of the rivers depositing these units were in the range of 10−4 to 10−3, based on paleohydraulic calculations. However, depositional thickness trends of these units are not sufficient to have generated such steep paleoslopes. Thus, long wavelength tilting of the Earth's surface must have occurred for these gravels to be transported. Although these units were deposited adjacent to large tectonic features, including an evolving and migrating continental arc, and, for the Ogallala Group, the northward-propagating Rio Grande Rift, the tilting occurred over wavelengths too broad to be directly generated by these features. These widespread gravel units attest to the interplay between the creation of subduction-related isostatic and dynamic topography and continental sedimentation. Hence, paleotopography, as determined from calculated transport gradients of sedimentary deposits, provides a means of relating constructional landforms to mantle-driven processes. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

OSWALDPEETERSITE, (UO2)2CO3(OH)2{middle dot}4H2O, A NEW BASIC URANYL CARBONATE MINERAL FROM THE JOMAC URANIUM MINE, SAN JUAN COUNTY, UTAH, U.S.A.

Oswaldpeetersite, ideally (UO 2 ) 2 CO 3 (OH) 2 ·4H 2 O, is a newly discovered hydrated basic uranyl carbonate mineral found in the Jomac uranium mine, Brown’s Rim, San Juan County, Utah, U.S.A. It occurs along some bedding planes of a layer of siltstone within the Triassic Shinarump conglomerate. Associated minerals are gypsum, cuprite, antlerite, goethite, lepidocrocite, mbobomkulite, hydrombobomkulite, sklodowskite and two undefined uranium minerals. Oswaldpeetersite occurs as micrometric prismatic crystals (approximately 0.1 × 1 × 02 mm). These are canary yellow and transparent, with a vitreous luster and pale yellow streak. It does not fluoresce in ultraviolet radiation. The H Mohs is in the range 2–3. D meas > 4.10 g/cm 3 , D calc = 4.54 g/cm 3 (empirical formula), 4.50 g/cm 3 (idealized formula). Optically biaxial negative, α 1.583(2), β 1.669(2), γ 1.712(2), and 2 V calc = 67.4(2)°. Orientation Z || a and elongation positive. The pleochroism is X and Y very pale yellow to colorless, and Z pale yellow. The cleavage and parting are along the elongation. The tenacity is weak, and the fracture, uneven. The habit can be described as acicular. Oswaldpeetersite is monoclinic, P 2 1 / c , with unit-cell parameters refined from powder data: a 4.1425(6), b 14.098(3), c 18.374(5) A, β 103.62(1)°, V 1042.8(3) A 3 , a:b:c = 0.2938:1:1.3033 and Z = 4. The forms recognized are {100}, {010} and {001}. The strongest eight reflections of the X-ray powder pattern [ d (in A)( I )( hkl )] are: 8.95(65)(002), 7.54(63)(012), 4.55(96)(031), 4.26(60)(014), 3.46(62)(015), 3.32(100)(114), 3.029(85)(043) and 2.273(62)(062). Electron-microprobe and thermogravimetric analyses gave UO 3 81.47 and H 2 O 12.30 wt.%. The CO 2 content was calculated as 6.23 wt.% by difference. The oxide formula is 2.03 UO 3 ·1.01 CO 2 ·4.88 H 2 O, and the empirical formula is (UO 2 ) 2.03 (CO 3 ) 1.01 (OH) 2.05 ·3.85 H 2 O. The name honors the Belgian structural crystallographer Maurice Oswald Peeters, University of Leuven, Belgium.

Shelf-to-Basin Lower Triassic Sediments Across Las Vegas Hingeline, Nevada: ABSTRACT

Lower Triassic Moenkopi (Formation of McKee, 1954; Group of Poborski, 1954) changes facies with increase in thickness from mostly nonmarine and minor marine character east of Las Vegas, Nevada, to progressively more marine character toward the west as the Las Vegas hingeline is crossed. The thickness of Moenkopi strata east of this hinge in the Rainbow Garden area (east of Frenchman Mountain) is 1,810 ft, of which about 350 ft is the marine Virgin Limestone. About 20-22 mi farther east, Moenkopi aggregates about 1,250 ft; this section contains more redbed but less carbonate and gypsiferous facies than at Rainbow Gardens. Outcrops west of the hinge in the expanse between Las Vegas and east Blue Diamond Mountain show a progressive increase in Moenkopi thickness, with more marine sediments; Virgin Limestone is about 500 ft thick. A much more striking change takes place westward, End_Page 520------------------------------ toward the west side of Blue Diamond Mountain, where the Virgin Limestone consists of 900 ft of marine limestone, dolostone, claystone, and shale; weaker units in the Moenkopi are covered largely by alluvium. About 6-8 mi farther south, in the Cottonwood Wash-Bird Spring Range area, total Moenkopi is about 2,000 ft, of which Virgin Limestone consists of 1,025 ft of cyclically accumulated marine limestone, dolostone, claystone, and shale. The leading edge of the Keystone overthrust is 2-3 mi west of Triassic outcrops of the Blue Diamond Mountain-Bird Spring Range localities; Triassic strata on the upper plate are exposed superbly in the Lovell Wash-Lovell nose area, and in the Grapevine Springs locality near Kyle Canyon, about 10-15 mi west and northwest, respectively, from the Blue Diamond locality. Total thickness of interbedded and cyclically accumulated marine limestone, shale, and claystone is at least 2,435 ft; west-dipping strata are beneath Quaternary alluvium. Lower Triassic strata of the autochthonous sections east of the Keystone overthrust are disconformable on the Harrisburg Member (gypsiferous) of the Kaibab Formation in most localities, and in turn are overlain disconformably by Shinarump Conglomerate. In the allochthonous block, however, the Harrisburg Member is absent, and only locally do Lower Triassic sediments lie on the Kaibab; elsewhere, channels were cut through the Kaibab and Toroweap, and the Mesozoic sediments have thick cobble and boulder conglomerate resting with marked unconformity on Permian redbeds. End_of_Article - Last_Page 521------------

Possible eddy markings in the Shinarump conglomerate of northeastern Utah

Spiral impressions in sandstone of the Shinarump conglomerate (Triassic) occur about 10 mi. N of Vernal on the southern flank of the Uinta Mountains, Utah. The impressions are 1-3 ft. in diameter and have been cut 1/4 to 1/2 in. deep into the sandstone bedding surface. The spirals may have originated from movement of a tree branch caught in a vortex or eddy current of a stream that deposited the sandstone.

Proposed Nomenclature of Part of Upper Triassic Strata in Southeastern Utah

The Triassic rocks in southeastern Utah have been divided into the Moenkopi formation of Early and Middle (?) Triassic age, and the Shinarump conglomerate, Chinle formation, and Wingate sandstone of Late Triassic age. Recent work has shown that the strata formerly called Shinarump conglomerate in southeastern Utah consist, in places, of a lower sandstone and conglomerate unit, a middle claystone and clayey sandstone unit, and an upper sandstone and conglomerate unit. The lower and upper units are Shinarump-type deposits whereas the middle unit is a Chinle-type deposit. Deposits of Shinarump-type and Chinle-type are interstratified and intertonguing. The writer proposes that the two types be grouped together in the Chinle formation and that the Shinarump conglomerate be re efined as the Shinarump member of the Chinle formation. The lower unit is correlative with strata in southwestern Utah, that are designated as type Shinarump conglomerate, and the writer proposes that the term Shinarump member be restricted in southeastern Utah to this lower unit. The middle and upper units, although formerly included in the Shinarump conglomerate, are considered as separate members of the Chinle formation. The middle unit has been defined as the Monitor Butte member of the Chinle formation, and the name Moss Back member is here proposed for the upper unit. In southeastern Utah, the Shinarump conglomerate included, in places, all of the Shinarump, Monitor Butte, and Moss Back members of the Chinle formation. In other places, the Shinarump conglomerate consisted only of the Moss Back member, and in still other parts of southeastern Utah the Shinarump conglomerate consisted of only the Shinarump member. Locally in the San Rafael Swell area, Emery County, a thin unit now called Temple Mountain member was included by previous workers in the Shinarump conglomerate. In addition to subdividing the strata previously included in the Shinarump conglomerate, the overlying part of the Chinle formation has been subdivided into members. As now recognized, the Chinle formation consists of seven members in southeastern Utah. They are, in ascending order, the Temple Mountain, Shinarump, Monitor Butte, Moss Back, Petrified Forest, Owl Rock, and Church Rock members.

Uranium ore guides, Monument Valley District, Arizona

The contact between the Shinarump conglomerate and the Moenkopi formation, both of Triassic age, is a marked erosional unconformity. Basal Shinarump sediments fill ancient stream channels incised into the underlying Moenkopi. On the Colorado Plateau uranium ore deposits are commonly found in these stream channels. Paleostream channels are the prime guide to ore in the Shinarump. Twenty-seven others of varying degrees of usefulness are summarized.

Uranium ore controls of the Happy Jack deposit, White Canyon, San Juan County Utah

The major uranium ore control of the Happy Jack uranium deposit of White Canyon, San Juan County, Utah, is a paleostream channel containing sediments of the Shinarump conglomerate. Intrachannel controls include organic matter, lithologic variations, and channel lows.Microscopic studies reveal that uraninite, the primary ore mineral, occurs as cement and as a replacement of organic material. Both uraninite and copper sulfides replace secondary quartz overgrowths. Uraninite is dated as later than the secondary overgrowths and of about the same age as the copper sulfides.

Exploration Frontiers in Mesozoic Sediments of Four Corners Region: ABSTRACT

The Four Corners region includes 40,000 square miles in New Mexico, Colorado, Utah, and Arizona and is underlain by Mesozoic sediments. Within this area, 21,000 square miles are underlain by sediments at depths favorable for oil or gas production in at least one formation. The present development of oil and gas fields in this area was foreshadowed by shows of oil and gas in early wells, and by seeps in outcrop areas. Much of the present significant production is associated with stratigraphic changes in the formations which produce. End_Page 951------------------------------ The Triassic Shinarump conglomerate, the Jurassic Entrada sand, the uppermost Jurassic Morrison(?) sand, the Upper Cretaceous Dakota-Graneros sands, and many other Upper Cretaceous sands intertonguing with the Mancos and Lewis shales have a record of oil and gas shows which has not been fully exploited in 90 per cent of the favorable area. Exploration frontiers associated with sedimentation exist as overlooked variations in deposition, development, and permeability of the Mesozoic sands. Frontiers associated with structure exist with possibility of fault traps, permeability traps, and hydrodynamic traps on low plunging folds with no apparent surface closure. Closure may exist on these folds in the pre-Cretaceous sediments. The known lithologic variations of the many possible reservoir beds, when combined with known regional structural anomalies, point to many areas of possible production in the sands with a proved record of shows. End_of_Article - Last_Page 952------------

Identification and Lead-Uranium Ages of Massive Uraninites from the Shinarump Conglomerate, Utah

Identification and Lead-Uranium Ages of Massive Uraninites from the Shinarump Conglomerate, Utah

CENOZOIC GRAVELS ON THE RIM OF SYCAMORE CANYON, ARIZONA

Cenozoic gravels along the rim of Sycamore Canyon are of two types: one containing rounded pebbles derived locally from the Shinarump conglomerate and developed in Pleistocene-Recent time; the other, angular pebbles derived from rocks similar to those exposed today in the Black Hills-Bradshaw Mountains area to the southwest and developed in the Miocene or Pliocene. The angular gravels were laid down, not upon a peneplain as suggested by Robinson, D. W. Johnson, et al ., but upon a pediment that extended northeastward from the mountains and covered that area of the Colorado plateau now occupied by Sycamore Canyon.

A Primitive Stone Industry of the Little Colorado Valley, Arizona

About eight years ago there was discovered in the valley of the Little Colorado River between Hoi brook and Cameron in northern Arizona, evidence of an ancient alluvial terrace. Sand and waterworn pebbles largely derived from the Triassic Shinarump Conglomerate that once covered the area, form the deposit. The terrace which was formed by the gravels is now much dissected and remains only as the isolated flat tops of hills and ridges, the surfaces of which are covered with a desert pavement of waterworn pebbles. There are remnants also of later and lower alluvial deposits containing angular fragments of rock, of which a large proportion is made up of basaltic rocks from the San Francisco Peaks (Fig. 22).

Correlation of the Permian of Southern Utah, Northern Arizona, Northwestern New Mexico, and Southwestern Colorado

The Permian of southern Utah, northern Arizona, northwestern New Mexico, and southwestern Colorado is conceived as bounded below, except in the Grand Canyon, by conformable Pennsylvanian limestone (Callville limestone in the extreme west, an unnamed unit in north-central Arizona, Hermosa formation in San Juan Valley and southwestern Colorado, Magdalena limestone in northwestern New Mexico), and above by unconformable Triassic deposits (Moenkopi formation, Shinarump conglomerate, and Dolores formation, in order from west to east). In the Grand Canyon the underlying beds are Mississippian (Redwall) limestone. Three main types of Permian sequence occur: that of the Grand Canyon, with the Supai formation and Hermit shale (red beds), Coconino sandstone (light-colored, cross-be ded), and Kaibab limestone, named in ascending order; that of Monument Valley and adjacent country north and south, with the Rico formation (red beds and limestone) below and five units above, here treated as parts of the Cutler formation and named in ascending order the Halgaito tongue (red beds), Cedar Mesa sandstone member (light-colored, cross-bedded), Organ Rock tongue (red beds), De Chelly sandstone member (light-colored, cross-bedded), and Hoskinini tongue (red beds); that of southwestern Colorado, with the Rico formation (red beds and limestone) below and the undivided Cutler formation (red beds) above. The relations of these units to one another are shown in a number of cross sections and the earlier nomenclatures are correlated with that used here. Apparently the Permian began ith the widespread deposition of red beds derived from the east, except in the extreme west part of the area where light-colored sands were laid down. In the east a few marine limestones (Rico) interrupted the sequence of red materials, representing incursions of a sea from the east. These first red deposits were followed by light-colored sands coming from the northwest (Cononino, et cetera), which interfingered End_Page 1413------------------------------ with the red materials that still continued to come in from the east. Then marine waters gradually advanced from the west across the western half of the area, depositing chiefly limestone (Kaibab). East of the sea the light-colored sandstones were the chief deposits in a wide zone, and still farther east the red materials prevailed. Finally, the sea withdrew with seeming abruptness and the whole area was exposed to the period of erosion represented by the unconformity at the base of the Triassic.

Notes on the Stratigraphy of the Moab Region, Utah

Results of work near Moab, Utah, by U. S. Geological Survey field parties in 1926 in part accord with and in part differ from current interpretations. In the Salt Valley anticline lower Mississippian rocks occur as limestone boulders in a conglomerate of unknown age. The oldest rocks in place at the surface are Pennsylvanian (Hermosa formation), sharply separated from the Permian by contained marine faunas. The Permian formations (Rico and Cutler) are not sharply separated. The former contains marine limestones; the latter, tongues of white sandstone that increase southwestward and at top the sandstone member (De Chelly?) locally known as the White Rim. The Lower Triassic Moenkopi formation, including in Green River Valley a marine limestone member, rests with unconformit upon Cutler and is in turn overlain unconformably by Upper(?) Triassic Shinarump conglomerate. Shinarump grades upward into the Chinle formation and is not recognizable as a separate unit at many localities, especially toward the east. A group of Jurassic(?) formations, including Wingate and Navajo sandstones separated by the Todilto(?) formation, rests unconformably upon the Chinle. The formations of the group are conformable and have arbitrary common boundaries. The succeeding Carmel and Entrada formations (Upper Jurassic) are similar to this group. The Carmel formation may overlie the Navajo sandstone with unconformity. Summerville formation (Upper Jurassic) intertongues with the underlying Entrada sandstone so that Entrada lithology extends higher toward the east. Summerville is sep rated by an unconformity from the overlying Salt Wash sandstone member of the Morrison formation (Cretaceous?). Dakota(?) sandstone (Upper Cretaceous) rests unconformably upon the Morrison formation and is succeeded by the Mancos shale. The stratigraphy would seem to indicate the following events in the history of the region: Possibly folding and erosion between lower Mississippian and Pennsylvanian; folding and erosion at the close of the Permian; erosion and possibly folding between Lower and Upper Triassic, and between Upper Triassic and Jurassic(?) (Wingate); possibly erosion preceding Upper Jurassic (Carmel); erosion between Upper Jurassic and Cretaceous(?) (Morrison), and between Cretaceous(?) and Upper Cretaceous. End_Page 785------------------------------