Bluff Sandstone Research Articles

The Morrison Formation and its bounding strata on the western side of the Blanding basin, San Juan County, Utah

In 2016 and 2017, the Utah Geological Survey partnered with the U.S. Bureau of Land Management to conduct a paleontological inventory of the Morrison Formation south and west of Blanding, Utah, along the eastern margin of the Bears Ears National Monument. The Morrison in this region is critical to understanding Upper Jurassic stratigraphy across the Colorado Plateau because it is the type area for the Bluff Sandstone, Recapture, Westwater Canyon, and Brushy Basin Members of the Morrison Formation, which are the basis for nomenclature in New Mexico and Arizona as well. Researchers have disagreed about nomenclature and correlation of these units, which transition northward in the study area into the Tidwell, Salt Wash, and Brushy Basin Members. Numerous vertebrate localities make inclusion of the Bluff Sandstone and Recapture Members in the Middle Jurassic San Rafael Group, as suggested by some previous workers, unlikely. The Salt Wash Member does not separate the Bluff Sandstone and Recapture Members at Recapture Wash, but sandstone lenses of Salt Wash facies occur higher in northern Recapture exposures. Northward, along the outcrop belt east of Comb Ridge, the Bluff-Recapture interval thins, interlenses, and pinches out into the Tidwell and lower Salt Wash, with the main lower sandstone interval of the Westwater Canyon merging northward into the upper Salt Wash Member.
 The partly covered, 1938 type section of the Brushy Basin Member is identified along Elk Mountain Road at the southern end of Brushy Basin. We describe a detailed, accessible Morrison Formation reference section about 11.2 km (7 mi) to the south along Butler Wash. There, 81.68 m (268 ft) of Brushy Basin Member is well exposed along a road between the top of the Westwater Canyon Member and the base of the Lower Cretaceous Burro Canyon Formation. We informally call the upper sandstone bed(s) of the Westwater Canyon Member that cap mesas and benches in the region “No-Mans Island beds.” Smectitic mudstones between the No-Mans Island beds and the main sandstone body of the Westwater Canyon suggest that the Salt Wash-Brushy Basin contact to the north may be somewhat older than the base of the Brushy Basin Member as originally defined in its type area. Determining whether the No-Mans Island beds pinch out to the north or are removed by erosion below the regional basal Brushy Basin paleosol requires further research. Several significant fossil vertebrate and plant sites have been documented in the Brushy Basin type area. Newly identified volcanic ashes provided zircons for U-Pb ages of 150.67 ± 0.32 Ma from near the top of the Brushy Basin Member and of 153.7 ± 2.1 Ma and 153.8 ± 2.2 Ma for two zircons in lower part of Recapture Member. At the top of the Brushy Basin Member, ferruginous paleosols commonly overlying conglomeratic sandstone are speculated to be of Early Cretaceous age (detrital zircon age pending) and are assigned herein to the Yellow Cat Member of the Burro Canyon Formation. These iron-rich paleosols suggest wetter climatic conditions during the Jurassic-Cretaceous transition in the Blanding basin.

Depositional facies and extent of the late Neogene Sandringham Sandstone in southern Victoria, Australia

The late Neogene sedimentary rocks in the Port Phillip region have in the past been subdivided into a lower shallow marine unit, Black Rock Sandstone, overlain by a fluvial unit, Red Bluff Sandstone. Re-examination of the type section of these units at Sandringham shows that it is entirely of paralic origin, with no evidence for fluvial deposition. Criteria for interpreting a shallow marine origin are sedimentary structures including a planar bedding style and swaley cross-stratification, and highly rounded clasts in conglomerates. Using these criteria it can be demonstrated that all named late Neogene sedimentary rock units in the Port Phillip region are paralic deposits, and that the same applies to the Hanson Plain Sand of the Port Campbell Embayment. Because these were deposited as a continuous sheet, the multiplicity of names used hitherto is not justified and should be unified under the single name Sandringham Sandstone. This formation was deposited on a strandplain that extends across western Victoria to the southern fringe of the Western Uplands. The same lateral continuity applies to the underlying Miocene marl formation, which is unified under the name Gellibrand Marl.

Mid-Cretaceous (Albian–Cenomanian) freshwater Mollusca from the Clarence Valley, Marlborough, New Zealand, and their biogeographical significance

Mollusca from the Warder Formation in the middle Clarence Valley, Marlborough, are the first well-preserved Cretaceous freshwater Mollusca recorded from New Zealand. They include a common mytilid (?Mytilus), a rare second mytilid (?Xenostrobus), a rare hyriid (?Echyridella), a common smooth ?Corbicula species and a rare commarginally sculptured one, an uncommon thiarid (?Melanoides), a rare lymnaeid (?Austropeplea), and abundant Clarenciella hippopedion n. gen., n. sp., a rissooidean gastropod referred to Cochliopidae. The Warder Formation underlies Gridiron Volcanics (97–95 Ma) and is laterally equivalent to the Bluff Sandstone, which contains a marine Ngaterian fauna (99.5–95.2 Ma, late Albian–Cenomanian). The freshwater fauna lived before New Zealand began to separate from the rest of Gondwana (85 Ma). Faunal elements lost from New Zealand since the Cretaceous include Cyrenidae and Cochliopidae, which are diverse in the South American Cenozoic and living freshwater faunas. In contrast, Hyriidae have a continuous Jurassic–Recent record in New Zealand and are among freshwater taxa that survived both the fragmentation of Gondwana and the putative Oligocene submergence. These and other archaic endemic freshwater taxa such as Latia (Gastropoda, Chilinoidea) remain a vestige of New Zealand’s Gondwanan heritage, modified by extinction, evolution and dispersal.

A model for uranium mobility in groundwater in the Grand Pré region, Nova Scotia, Canada

Elevated levels of uranium that surpass maximum allowable concentrations have been recognized in some well water samples throughout Nova Scotia. In this study we examine the influence of redox conditions and regional geology on the mobility of uranium in groundwater in the Grand Pré region, located in the eastern end of the Annapolis-Cornwallis Valley in southwestern Nova Scotia. The study site is underlain by carbon-rich shale and arkosic sandstone of the Late Mississippian Horton Bluff Formation and the arenaceous sandstone of the Triassic Wolfville Formation. Water samples from drilled wells were analyzed on site for various water quality parameters (pH, conductivity, temperature, dissolved oxygen) and in the laboratory to determine alkalinity and cation (72) and major anion (9) concentrations.
 
 Several samples exceeded Health Canada (2011) limits for uranium (20 μg/L) with values up to 50.8 μg/L and aesthetic objectives (AO) for iron (up to 605 μg/L), manganese (up to 2.28 mg/L) and other cations. Data show that different redox conditions occur in the study area. The geospatial arrangement of the chemical data suggests that the lithology of the underlying aquifer strongly influences the availability of uranium in groundwater. Reduced groundwater in Horton Bluff sandstone typically contains elevated concentrations of Fe 2+ and Mn 2+ , whereas groundwater containing high concentrations of U is found primary in oxidizing environments in quartz arenite sandstone units in the Wolfville Formation.
 
 Consumption of groundwater in the Grand Pré region may pose a health risk; however, the level of risk remains unknown. This study emphasizes that in the area of Grand Pré, water that is considered aesthetically undesirable (containing high Fe and Mn) may pose less of a health risk (low U) than waters that are aesthetically pleasing.

Paleomagnetic and rock magnetic evidence for a secondary yet early magnetization in large sandstone pipes and host Late Middle Jurassic (Callovian) Summerville Formation and Bluff Sandstone near Mesita, west central New Mexico

Processes responsible for the acquisition of ancient yet secondary magnetizations are important facets of the geologic history of rocks and, when the age of such magnetizations can be estimated with confidence, provide useful information on the ancient geomagnetic field. In west central New Mexico near Mesita, on the Colorado Plateau, hematitic sandstone and siltstone beds of the Middle Jurassic (Callovian) Summerville Formation and overlying Bluff Sandstone are host to numerous large (up to 100 m2 in map area) pipe‐like sandstone bodies. The pipes are as strongly cemented by hematite (colors range from 10R 6/6 to 10R 3/4) as the host strata; paleomagnetic data from them and their host strata are interpreted to indicate that these rocks have been remagnetized, probably in association with sandstone pipe formation. Reverse polarity magnetizations isolated in both alternating field and thermal demagnetization from pipes are well grouped and are similar to, and not statistically distinct from, those in adjacent host strata. The grand‐mean direction for 16 sites (7 sites in sandstone pipes and 9 in host strata), corrected for slight (5°) west‐northwest tilt of the strata, is D = 163.0°, I = −44.3° (α95 = 2.7°, k = 169). This direction yields a pole position of 72.8°N, 135.7°E (dp = 2.1°, dm = 3.4°). Assuming a modest (i.e., ∼5°) clockwise rotation of the Colorado Plateau, the pole lies at 68.7°N, 143.8°E. Median destructive fields for the remanence in pipes and host strata are typically 40–50 mT; over 90% of the remanence is “unblocked” or removed during changes in the magnetic mineralogy by temperatures of ∼400–450°C. Isothermal remanent magnetization (IRM) acquisition data, and thermal demagnetization of “saturation” IRM, however, demonstrate that the dominant magnetic phase is of high coercivity and relatively high (above 600°C) laboratory unblocking temperatures in both sandstone pipes and host strata, yet it does not appear to contribute significantly to the characteristic remanent magnetization. The similarity in demagnetization properties between pipes and adjacent host strata, the absence of a well‐defined high unblocking temperature remanence that is more typical of hematite‐cemented detrital strata, and the essentially uniform reverse polarity of the remanence are all interpreted to indicate that pipes and host strata contain secondary, yet early acquired magnetizations and that magnetization acquisition continued after pipe injection. We propose that acquisition of the secondary magnetization took place in the presence of alkaline, high pH brines formed by the dissolution of the underlying gypsum‐dominated Lower Jurassic Todilto Formation strata and therefore the remanence is early in age. On the basis of a comparison with Summerville and Morrison (Middle and Late Jurassic) paleomagnetic poles from rocks on the Colorado Plateau, we interpret the secondary remanence in Summerville strata and sandstone pipes near Laguna to be latest Middle to Late Jurassic in age. If realistic, this interpretation further emphasizes the importance of fluid‐rock interaction in the acquisition of secondary magnetizations.

Stratigraphy and structure of the Monkey Face area, Marlborough, New Zealand, with special reference to shallow marine Cretaceous strata

Abstract The Monkey Face area, southern Marlborough, New Zealand, lies on the boundary between the East Coast Deformed Belt and the Canterbury Basin. Late Jurassic–Early Cretaceous Torlesse rocks are overlain unconformably by Motuan–?Arowhanan (Albian–?Cenomanian) Gridiron Formation, comprising nonmarine Warder Coal Measures Member and shallow marine Bluff Sandstone Member. The Bluff Sandstone Member recordssedimentationonawave-dominatedcoastline in what may have been a local subsiding asymmetric fadt-controlledbasin.OverlyingGridironFormation is a thin unnamed Piripauan or lowest Haumurian (Campanian) greensand unit, formation A. Disconformably overlying this is Haumurian (Maastrichtian) Conway Formation, which, in turn, is separated by a disconformity from Eocene Amuri Limestone. The top of the Amuri Limestone is not exposed, and a small block of Altonian (late Early Miocene) Waima Formation is fault bounded. Folding and complex faulting of the area is thought to result from post-Altonian dextral movement of the Hope Fault during the Kaikoura Orogeny. This deformation continues today.

Synthesis of late Paleozoic and Mesozoic eolian deposits of the Western Interior of the United States

Late Paleozoic and Mesozoic eolian deposits include rock units that were deposited in ergs (eolian sand seas), erg margins and dune fields. They form an important part of Middle Pennsylvanian through Upper Jurassic sedimentary rocks across the Western Interior of the United States. These sedimentary rock units comprise approximately three dozen major eolian-bearing sequences and several smaller ones. Isopach and facies maps and accompanying cross sections indicate that most eolian units display varied geometry and complex facies relations to adjacent non-eolian rocks. Paleozoic erg deposits are widespread from Montana to Arizona and include Pennsylvanian formations (Weber, Tensleep, Casper and Quadrant Sandstones) chiefly in the Northern and Central Rocky Mountains with some deposits (Hermosa and Supai Groups) on the Colorado Plateau. Lower Permian (Wolfcampian) erg deposits (Weber, Tensleep, Casper, Minnelusa, Ingleside, Cedar Mesa, Elephant Canyon, Queantoweap and Esplanade Formations) are more widespread and thicken into the central Colorado Plateau. Middle Permian (Leonardian I) erg deposits (De Chelly and Schnebly Hill Formations) are distributed across the southern Colorado Plateau on the north edge of the Holbrook basin. Leonardian II erg deposits (Coconino and Glorieta Sandstones) are slightly more widespread on the southern Colorado Plateau. Leonardian III erg deposits formed adjacent to the Toroweap-Kaibab sea in Utah and Arizona (Coconino and White Rim Sandstones) and in north-central Colorado (Lyons Sandstone). Recognized Triassic eolian deposits include major erg deposits in the Jelm Formation of central Colorado-Wyoming and smaller eolian deposits in the Rock Point Member of the Wingate Sandstone and upper Dolores Formation, both of the Four Corners region. None of these have as yet received a modern or thorough study. Jurassic deposits of eolian origin extend from the Black Hills to the southern Cordilleran arc terrain. Lower Jurassic intervals include the Jurassic part of the Wingate Sandstone and the Navajo-Aztec-Nugget complex and coeval deposits in the arc terrain to the south and west of the Colorado Plateau. Major Middle Jurassic deposits include the Page Sandstone on the Colorado Plateau and the widespread Entrada Sandstone, Sundance Formation, and coeval deposits. Less extensive eolian deposits occur in the Carmel Formation, Temple Cap Sandstone, Romana Sandstone and Moab Tongue of the Entrada Sandstone, mostly on the central and western Colorado Plateau. Upper Jurassic eolian deposits include the Bluff Sandstone Member and Recapture Member of the Morrison Formation and Junction Creek Sandstone, all of the Four Corners region, and smaller eolian deposits in the Morrison Formation of central Wyoming and apparently coeval Unkpapa Sandstone of the Black Hills. Late Paleozoic and Mesozoic eolian deposits responded to changing climatic, tectonic and eustatic controls that are documented elsewhere in this volume. All of the eolian deposits are intricately interbedded with non-eolian deposits, including units of fluvial, lacustrine and shallow-marine origin, clearly dispelling the myth that eolian sandstones are simple sheet-like bodies. Rather, these units form some of the most complex bodies in the stratigraphic record.

Sandstone Pipes of the Laguna Area, New Mexico

Strata of Jurassic age contain cylindrical bodies of sandstone called pipes. They cut gently dipping strata in the Summerville Formation, Bluff Sandstone, and Morrison Formation near Laguna, Now Mexico. The pipes range from a few feet to a few hundred feet in height, and from a few inches to 130 ft in width. Petrographic studies of the material in the pipes and of the enclosing strata show that the pipes are composed of reworked subarkosic sandstone derived from the uppermost units cut by the pipes. Some pipes are composed of brecciated sandstone and mudstone in a fine-grained matrix. The wall rocks sag downward around the pipes, and the pipes are bounded by one or more ring faults. The bottoms of the pipes are in sharp contact with the little-deformed underlying beds. The pipes formed during a period of gentle regional folding, and for the most part are located in belts near synclinal axes. Pipes originated during deposition of the uppermost sandstone units that contained them. They probably formed by gravitational foundering of sand into the underlying water-saturated mud. Some of the foundering may have been aided by solution and removal of underlying gypsum.

Heavy Minerals of Pre-Morrison Jurassic Rocks, Lucero Uplift, Northwestern New Mexico: ABSTRACT

A heavy-mineral study was made of the following formations in the Lucero uplift: Triassic: Chinle Formation and Wingate Sandstone; Jurassic: Carmel Formation, Entrada Sandstone, Todilto Formation (not analyzed), Summerville Formation, Bluff Sandstone, and Morrison Formation; Cretaceous: Dakota Sandstone. Emphasis was placed on the pre-Morrison Jurassic rocks. Heavy minerals identified from these rocks consist dominantly of zircon, garnet, tourmaline, rutile, and several opaque minerals, and very minor epidote, biotite, staurolite, and apatite. This limited suite of mostly rounded, stable heavy minerals indicates that the rocks concerned are multicycle sediments, and agrees with the conclusion previously derived from utilizing other stratigraphic tools in studying these rocks. Thus, in this respect, the usefulness of heavy minerals as a stratigraphic tool is demonstrated. Furthermore, the pre-Morrison part of the section, in which relatively abundant amounts of magnetite-ilmenite occur, is readily distinguishable from the Morrison Formation in which these minerals are virtually absent. When the pre-Morrison Jurassic rocks are viewed in sequence, it appears that the Carmel and lower Entrada are characterized by low zircon-garnet and high magnetite-ilmenite content, the upper Entrada by a high zircon-garnet and low magnetite-ilmenite content, and the Summerville and Bluff by a high zircon-low garnet and variable magnetite-ilmenite content. Nevertheless, with the exception of the upper Entrada, the differences in per cent distribution of the heavy minerals are not sufficient to unequivocally characterize any single pre-Morrison unit. Thus, in this respect the heavy minerals are not as useful a stratigraphic tool as they might be if the suite were mineralogically more varied. Prior to the determination of the heavy-mineral content by using standard techniques of counting individual grains, an attempt was made to estimate the heavy-mineral content. A comparison of the results of the two methods shows that, even with a simple suite of easily identifiable heavy minerals, an estimated per cent distribution is not reliable and does not justify the apparent saving in time. End_of_Article - Last_Page 273------------

Clay Minerals in the Morrison Formation on the Colorado Plateau

Clay Minerals in the Morrison Formation on the Colorado Plateau

Morrison formation and related deposits in and adjacent to the Colorado Plateau

Research Article| August 01, 1944 Morrison formation and related deposits in and adjacent to the Colorado Plateau WILLIAM LEE STOKES WILLIAM LEE STOKES Search for other works by this author on: GSW Google Scholar Author and Article Information WILLIAM LEE STOKES Publisher: Geological Society of America Received: 04 Jun 1942 First Online: 02 Mar 2017 Online Issn: 1943-2674 Print Issn: 0016-7606 © 1944 Geological Society of America GSA Bulletin (1944) 55 (8): 951–992. https://doi.org/10.1130/GSAB-55-951 Article history Received: 04 Jun 1942 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 WILLIAM LEE STOKES; Morrison formation and related deposits in and adjacent to the Colorado Plateau. GSA Bulletin 1944;; 55 (8): 951–992. doi: https://doi.org/10.1130/GSAB-55-951 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 Morrison formation in and adjacent to the Colorado Plateau currently includes diverse lithic units, many of which cannot properly be included if the limitations of the type section and relationships to other formations are considered. The Todilto limestone, Bluff sandstone, Wanakah marl, Pony Express limestone, and Bilk Creek sandstone can be correlated with the San Rafael group and dated as Upper Jurassic by the marine beds in the group. The Salt Wash sandstone, Brushy Basin shale, Recapture Creek sandstone, and Westwater Creek sandstone are considered equivalent to the type Morrison and have yielded vertebrate remains and are almost certainly Jurassic. Succeeding these are two new formations, the Buckhorn conglomerate and Cedar Mountain shale, which have yielded no fossils but are tentatively classed as Lower Cretaceous, mainly by analogy with similar deposits in adjacent areas.Lithology, distribution, and paleogeography of all units are discussed, and changes in nomenclature and correlation are recommended. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Correlation of Cross' La Plata Sandstone, Southwestern Colorado

The Upper Jurassic La Plata sandstone, described by Cross as essentially two thick sandstones with a thin limestone between, is shown to consist typically of the following units in ascending order. Unit 1 is the Entrada sandstone, a massive, partly cross-bedded, yellowish to red sandstone. Unit 2 is discontinuous bituminous, thin-bedded limestone, in places associated with gypsum, attaining a thickness of 15 feet, and named the Pony Express limestone member of the Morrison formation. Unit 3 is sandstone or sandy beds about 20 feet thick here named the Bilk Creek sandstone member of the Morrison. At the top of this member there is a sandstone about 1½-2 feet thick, with coarse rounded grains and autochthonous red chert, called carnelian sandstone. Unit 4 consists of 5 -100 feet of red, sandy, cherty marls, named the Wanakah marl member of the Morrison, a restriction of the name to only that part of the section to which it was originally applied. The Wanakah marl contains crystals or concretions of barite and a zone of chert concretions coated with a green mineral. This zone is a valuable diagnostic bed in correlation. Unit 5 is massive, cross-bedded, whitish sandstone attaining a thickness of 500 feet, here named Junction Creek sandstone member of the Morrison. In places beds of Wanakah type overlie the Junction Creek sandstone and make it more difficult to draw, the boundary against the overlying beds. Unit 1, the Entrada, is Cross' lower La Plata sandstone. Unit 5 is thickest in the La Plata Mountains and is the upper La Plata sandstone of that region. In the Telluride region, where this bed is poorly developed or absent, the Bilk Creek sandstone (unit 3) has been called upper La Plata sandstone. In other areas, where both the Pony Express limestone (unit 2) and the Junction Creek sandstone (unit 5) are absent or poorly developed, the Bilk Creek sandstone has been regarded as part of the Entrada, and beds probably younger than the Junction Creek have been called upper La Plata sandstone. We believe that units 2 and 3 are equivalent to the Curtis of east-central Utah, and unit 4 to the Summerville, and that unit 5, the Junction Creek sandstone, hitherto recognized only as the upper a Plata sandstone of the La Plata Mountains, bears more resemblance to the Wingate, Navajo, and Entrada sandstones of the Utah section than to the overlying Morrison sandstones. Pending further studies in this area they are, however, all classed here as members of the Morrison formation. In southeastern Utah the Bluff sandstone member of the Morrison may be equivalent to the Junction Creek. We incline to Gregory's interpretation that the Todilto limestone in Todilto Park is overlain by the Navajo sandstone and is, therefore, not equivalent to the Pony Express limestone; but on Beclabito (Biltabito) Dome in the northwest corner of New Mexico, the limestone called Todilto lies on the Entrada, is overlain by beds resembling the Wanakah, and we, therefore, consider it equivalent to the Pony Express. Possible equivalents of the Junction Creek sandstone in New Mexico are pointed out. A tentative correlation of a section along the Cimarron River, in the northeast corner of New Mexico, with the southwest Colorado section, is proposed. The presence, in places, of a series of y llowish sandy shales and regularly bedded, sideritic sandstones, that may be intermediate in position between the horizon of the top of the Junction Creek and the overlying Morrison sandstones, is pointed out.