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Channel- and lens-shaped deposits of non-eolian red sandstone are enclosed within the eolian Leche-e Member of the Page Sandstone in south-central Utah. Detailed analysis of lithology and geometry, and regional correlation of the red sandstone deposits suggests that the channel-shaped scours and in-filling deposits were formed by ephemeral stream processes, in contrast to earlier interpretations that suggested a marine estuarine origin. We hypothesize that ephemeral streams transporting volcanic debris flowed toward the north and northeast along the western edge of the Page erg. Local avulsion, possibly caused by eolian damming of an adjacent drainage, led to stream flow into low areas of the Page erg. Entrainment...
Channel- and lens-shaped deposits of non-eolian red sandstone are enclosed within the eolian Leche-e Member of the Page Sandstone in south-central Utah. Detailed analysis of lithology and geometry, and regional correlation of the red sandstone deposits suggests that the channel-shaped scours and in-filling deposits were formed by ephemeral stream processes, in contrast to earlier interpretations that suggested a marine estuarine origin. We hypothesize that ephemeral streams transporting volcanic debris flowed toward the north and northeast along the western edge of the Page erg. Local avulsion, possibly caused by eolian damming of an adjacent drainage, led to stream flow into low areas of the Page erg. Entrainment...
The Dakota Formation in southern Utah (Kaiparowits Plateau region) is a succession of fluvial through shallow-marine facies formed during the initial phase of filling of the Cretaceous foreland basin of the Sevier orogen. It records a number of relative sea-level fluctuations of different frequency and magnitude, controlled by both tectonic and eustatic processes during the Early to Late Cenomanian. The Dakota Formation is divided into eight units separated by regionally correlatable surfaces that formed in response to relative sea-level fluctuations. Units 1?6B represent, from bottom to top, valley-filling deposits of braided streams (unit 1), alluvial plain with anastomosed to meandering streams (2), tide-influenced...
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Caddisfly-dominated microbial-carbonate mounds and avian eggshell fragments are common in a nearshore, oolite facies of the Tipton Shale Member of the Eocene Green River Formation. The fossils occur in a 9 m thick carbonate sequence exposed on the south-west flank of Essex Mountain, Sweetwater County, Wyoming. The eggshell was determined to be of avian origin by examination of the radial eggshell microstructure by scanning electron microscopy and polarized light microscopy. Common allochems in the limestone include: ooids, pisoids, oncoids, ostracods, gastropods, intraclasts, caddisfly larval/pupal cases, fish bones, avian bones and avian eggshell fragments. Carbonate mineralogy varies between 95% calcite and 95%...
The effect of rock fragments and rock fragment cover on the accumulation of airborne dust was examined in a long-term field experiment in the Negev desert of Israel. Four parameters were studied: pebble eccentricity, pebble size, pebble flattening and cover density. The effect of these parameters on the accumulation of dust on the pebbles, on the accumulation of dust between and underneath the pebbles, and on total dust accumulation (pebbles+interpebble space) was measured separately. Accumulation on the pebbles increased as the pebbles became larger, less flattened and more elongated, and as cover density increased. Accumulation between and underneath the pebbles increased as the pebbles became smaller, more flattened...
Categories: Publication; Types: Citation, Journal Citation; Tags: Sedimentology
Experimental modelling of an aggrading braided river has allowed investigation of the relationship between the frequency of channel avulsion (Af), the duration of time that the braidplain is occupied by flow, the spatial pattern of braidplain sedimentation and how these respond to a change in sediment supply (Ss). Model results demonstrate a strong, positive relationship between Ss and Af and that there is no downstream change in Af over the short braidplain distances (ca 100 m) modelled herein. Although Af is strongly dependent on Ss, the degree of channel switching does not influence the rate, or spatial pattern, of braidplain sedimentation. All experiments used a single, central input for water and sediment,...
Categories: Publication; Types: Citation, Journal Citation; Tags: Sedimentology
The Permian Cedar Mesa Sandstone of south-east Utah is a predominantly aeolian succession that exhibits a complex spatial variation in sedimentary architecture which, in terms of palaeogeographic setting, reflects a transition from a dry erg centre, through a water table-controlled aeolian-dominated erg margin, to an outer erg margin subject to periodic fluvial incursion. The erg margin succession represents a wet aeolian system, accumulation of which was controlled by progressive water table rise coupled with ongoing dune migration and associated changes in the supply and availability of sediment for aeolian transport. Variation in the level of the water table relative to the depositional surface determined the...
The Campanian Cliff House Formation represents a series of individually progradational shoreface tongues preserved in an overall landward-stepping system. In the Mancos Canyon area, the formation consists of four, 50- to 55-m-thick and 10- to 20-km-wide sandstone tongues, which pinch out landwards into lower coastal plain and lagoonal deposits of the Upper Menefee Formation and seawards into offshore shales of the Lewis Shale Formation. Photogrammetric mapping of lithofacies along the steep and well-exposed canyon walls was combined with sedimentary facies analysis and mapping of the detailed facies architecture. Two major facies associations have been identified, one comprising the mostly muddy and organic-rich...
In settings where the transport of sand is partially or fully supply limited, changes in the upstream supply of sand are coupled to changes in the grain size of sand on the bed. In this manner, the transport of sand under the supply-limited case is ?grain-size regulated?. Since the closure of Glen Canyon Dam in 1963, the downstream reach of the Colorado River in Marble and Grand Canyons has exhibited evidence of sand-supply limitation. Sand transport in the river is now approximately equally regulated by changes in the discharge of water and changes in the grain sizes of sand on the channel bed and eddy sandbars. Previous work has shown that changes in the grain size of sand on the bed of the channel (driven by...
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Sandstone bodies in the Sunnyside Delta Interval of the Eocene Green River Formation, Uinta Basin, previously considered as point bars formed in meandering rivers and other types of fluvial bars, are herein interpreted as delta mouth-bar deposits. The sandstone bodies have been examined in a 2300 m long cliff section along the Argyle and Nine Mile Canyons at the southern margin of the Uinta lake basin. The sandstone bodies occur in three stratigraphic intervals, separated by lacustrine mudstone and limestone. Together these stratigraphic intervals form a regressive-transgressive sequence. Individual sandstone bodies are texturally sharp-based towards mudstone substratum. In proximal parts, the mouth-bar deposits...
The Permian Cedar Mesa Sandstone represents the product of at least 12 separate aeolian erg sequences, each bounded by regionally extensive deflationary supersurfaces. Facies analysis of strata in the White Canyon area of southern Utah indicates that the preserved sequences represent erg-centre accumulations of mostly dry, though occasionally water table-influenced aeolian systems. Each sequence records a systematic sedimentary evolution, enabling phases of aeolian sand sea construction, accumulation, deflation and destruction to be discerned and related to a series of underlying controls. Sand sea construction is signalled by a transition from damp sandsheet, ephemeral lake and palaeosol deposition, through a phase...
The origins and sedimentary features of grainfall-, avalanche-, and ripple-produced strata have been studied experimentally in a wind sedimentation tunnel. Rate of deposition, wind velocity and wind duration have been shown to control specific sedimentary features of these types of strata. Grainfall-produced strata were deposited on a horizontal surface, and surfaces sloping up to the angle of initial yield for dry sand (about 34�). Thickness of a grainfall-produced stratum depended upon rate of deposition and duration of a specific wind event. Grainfall-produced strata were both non-graded and graded. Graded strata were produced by changes in wind velocity which controlled size of sand in transport and flying distances...
Categories: Publication; Types: Citation, Journal Citation; Tags: Sedimentology
Dominantly coarse-grained, shallow-marine, metasedimentary rocks of the Early Proterozoic Uncompahgre Group (UG) record periods of shoaling and drowning on different temporal scales that are attributed to episodic long-term oscillations in relative sea-level with superimposed shorter duration excursions in relative sea-level. Long-term events are probably tectonic whereas short-term events are eustatic. The 2?5 km thick Uncompahgre Group consists of 250?600 m thick, dominantly coarse-grained quartzite units (Q1?Q4) and 200?300 m thick mudstone/pelite units (P1?P5). Five depositional systems comprise the Uncompahgre Group. The outer shelf system (OSS) is composed of Bouma-type beds and intercalated mudstones that...
Categories: Publication; Types: Citation, Journal Citation; Tags: Sedimentology
The Pennsylvanian to Permian lower Cutler beds comprise a 200 m thick mixed continental and shallow marine succession that forms part of the Paradox foreland basin fill exposed in and around the Canyonlands region of south-east Utah. Aeolian facies comprise: (i) sets and compound cosets of trough cross-bedded dune sandstone dominated by grain flow and translatent wind-ripple strata; (ii) interdune strata characterized by sandstone, siltstone and mudstone interbeds with wind-ripple, wavy and horizontal planar-laminated strata resulting from accumulation on a range of dry, damp or wet substrate-types in the flats and hollows between migrating dunes; and (iii) extensive, near-flat lying wind-rippled sandsheet strata....
Categories: Publication; Types: Citation, Journal Citation; Tags: Sedimentology
Detailed models already exist that outline physical and temporal relationships in marine and marginal marine strata. Such models are still in their infancy in alluvial deposits. Recognition of tidal and estuarine influence in fluvial strata is critical to the development of high resolution sequence stratigraphic correlations between marine and non-marine strata. Strata that have previously been interpreted as low energy meandering river deposits contain sedimentary and biogenic structures that suggest a tidal influence. These structures include sigmoidal bedding, paired mud/silt drapes, wavy and lenticular bedding, shrinkage cracks, multiple reactivation surfaces, inclined heterolithic strata, complex compound cross-beds,...
Categories: Publication; Types: Citation, Journal Citation; Tags: Sedimentology
The Upper Cretaceous (Campanian) Kenilworth Member of the Blackhawk Formation (Mesaverde Group) is part of a series of strand plain sandstones that intertongue with and overstep the shelfal shales of the western interior basin of North America. Analysis of this section at a combination of small (sedimentological) and large (stratigraphical) scales reveals the dynamics of progradation of a shelf-slope sequence into a subsiding foreland basin. Four major lithofacies are present in the upper Mancos and Kenilworth beds of the Book Cliffs. A lag sandstone and channel-fill shale lithofacies constitutes the thin, basal, transgressive sequence, which rests on a marine erosion surface. It was deposited in an outer shelf...
Categories: Publication; Types: Citation, Journal Citation; Tags: Sedimentology
The shore-normal transport of fine-grained sediments by shelf turbidity currents has been the focus of intense debate over the last 20 years. Many have argued that turbidity currents are unlikely to be a major depositional agent on the shelf. However, sedimentological, architectural, stratigraphic and palaeogeographic data from the Campanian Aberdeen Member, Book Cliffs, eastern Utah suggests otherwise and clearly demonstrates that storm-generated and river flood-generated underflows can transport a significant volume of fine-grained sediments across the shelf. These across-shelf flowing turbidity currents cut large subaqueous channel complexes up to 7 m deep, tens of kilometres basinward of their time-equivalent...
Integrated fluvial sequence stratigraphic and palaeosol analysis can be used to better reconstruct depositional systems, but these approaches have not been combined to examine halokinetic minibasins. This study characterizes the temporal and spatial patterns of lithofacies and palaeosols in a sequence stratigraphic framework to reconstruct a model of minibasin evolution and identify halokinetic influences on fluvial deposition. This research documents fluvial cycles and stratigraphic hierarchy, palaeosol maturity and apparent sediment accumulation rates in the Chinle Formation within the Big Bend minibasin. This study also uses palaeosols to help identify fluvial aggradational cycle (FAC) sets. The Chinle is divided...
The recognition of terminal fluvial systems, otherwise termed ‘terminal fans’ or ‘distributary fluvial fan systems’, preserved in the ancient rock record is based primarily on the recognition of facies characteristics indicative of a progressive downstream decrease in: (i) fluvial discharge; (ii) channel depth and width; (iii) lateral and vertical connectivity of channel-fill elements; and (iv) evidence for channellized flow and a systematic increase in: (i) evidence for sheetflood deposition; (ii) aeolian and/or playa deposits; and (iii) channel bifurcation. However, despite these criteria having been applied previously to a variety of outcrop successions, there is still no unifying facies model that adequately...
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The lower part of the Cretaceous Sego Sandstone Member of the Mancos Shale in east-central Utah contains three 10- to 20-m thick layers of tide-deposited sandstone arranged in a forward- and then backward-stepping stacking pattern. Each layer of tidal sandstone formed during an episode of shoreline regression and transgression, and offshore wave-influenced marine deposits separating these layers formed after subsequent shoreline transgression and marine ravinement. Detailed facies architecture studies of these deposits suggest sandstone layers formed on broad tide-influenced river deltas during a time of fluctuating relative sea-level. Shale-dominated offshore marine deposits gradually shoal and become more sandstone-rich...
map background search result map search result map Recognition and significance of sharp-based mouth-bar deposits in the Eocene Green River Formation, Uinta Basin, Utah Sharp-based, tide-dominated deltas of the Sego Sandstone, Book Cliffs, Utah, USA Palaeoenvironments associated with caddisfly-dominated microbial-carbonate mounds from the Tipton Shale Member of the Green River Formation: Eocene Lake Gosiute Recognition and significance of sharp-based mouth-bar deposits in the Eocene Green River Formation, Uinta Basin, Utah Sharp-based, tide-dominated deltas of the Sego Sandstone, Book Cliffs, Utah, USA Palaeoenvironments associated with caddisfly-dominated microbial-carbonate mounds from the Tipton Shale Member of the Green River Formation: Eocene Lake Gosiute