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Continental successions of the North American Western Interior retroarc foreland basin provide an excellent opportunity to evaluate the tectonic controls on nonmarine sequence stratigraphy. The transition between the Upper Jurassic Brushy Basin Member anastomosed fluvial system of the Morrison Formation and the gravelly braided-river deposits of the Buckhorn Conglomerate has been studied to assess the dispersal of coarse clastics and the development of associated basin-wide unconformities in a sequence stratigraphic framework. The sharp contact between the two members is interpreted to be conformable based on stratigraphic, sedimentologic, and petrologic data collected at and near Cedar Mountain in central Utah,...
The fossil-bone mineral in dinosaurs from the Morrison Formation is well-crystallized, stoichiometric francolite. The closely packed, subparallel francolite crystals have equidimensional cross sections mostly 10-40 nm wide. In contrast, crystallites in unaltered mammal bone tissue are poorly crystallized, nonstoichiometric carbonate hydroxyapatite, a few nanometers thick, and plate-, rod- or needle-shaped. The diagenetic francolite crystals are elongated in the c axis direction, as are bone-tissue crystallites. Along permeable cracks, francolite crystals grew to 250 nm wide. Compared to unaltered crystallites in mammal bones, the francolite has higher concentrations of Ba, Ce, Cr, F, La, Mn, Ni, Pb, Rb, Sr, Th,...
Interpretation of depositional environments combined with field measurement of permeability for a portion of the Upper Cretaceous Straight Cliffs Formation near Escalante, Utah, provides new results for understanding and modeling facies-dependent permeability variations. Offshore, transition-lower shoreface, upper shoreface, and foreshore environments are interpreted for part of the John Henry Member on the basis of outcrop investigation. Using a newly designed drillhole minipermeameter probe, permeability was measured for two of the facies within this unit: lower-shoreface bioturbated sandstone and upper-shoreface cross-bedded sandstone. Approximately 500 permeability measurements at a sample spacing of 15 cm were...
Basinal facies of the Green River Formation have two main modes, lacustrine and playa. The lacustrine mode (Tipton and Laney members) accumulated mainly varved oil shale. Here annual cycles are recorded as varves. Variations in verve thickness demonstrate El Nino (ENSO)-type and sunspot cycles (Ripepe et al., this volume). Milankovitch-scale cycles are not obvious in lithic variations, but gamma ray logs record 1) precessional variations with a mean period (varve-timed) of 19.5 ka, and 2) a bundling of these in the ca. 100 ka eccentricity cycle. In the playa mode (Wilkins Peak Member), the lithic succession oil shale-trona-dolomitic marlstone records the precessional drying up of a lake and is again bundled in sets...
Nonmarine sequence stratigraphic models hypothesize systematic changes in fluvial style within individual sequences and across sequence boundaries, based largely on mudstone-sandstone ratios. The main purpose of the paper is to evaluate the validity of these models by documenting facies relationships and detailed bedding architecture of bar and channel deposits as well as mudstone-sandstone ratio within a compound incised-valley fill at the top of the Cretaceous Ferron Sandstone Member of the Mancos Shale Formation in the Henry Mountains region, Utah, U.S.A. Field photomosaics, walking out of beds, and 42 measured sections document the stratal and facies organization in the incised-valley fill. Two erosional surfaces...
Laramide uplift and erosion of the Uinta Mountains are recorded in a 10-km-long outcrop of the Lower Eocene Wasatch Formation, on the Utah-Wyoming border. This 750-m-thick package of interbedded sandstones and conglomerates is dominated by a coarsening then fining-upward megasequence 650 m thick that records the growth and abandonment of a humid alluvial fun system during a major cycle of uplift and unroofing of the thrust-bounded northern flank of the Uinta mountains. Grain size, thickness, and lateral extent of channel-complex deposits increase upward in the lower 400 m of the sequence, reflecting construction and northward progradation of the fan. Grain size and channel-complex thickness decrease upward in the...
Nonmarine sequence stratigraphic models hypothesize systematic changes in fluvial style within individual sequences and across sequence boundaries, based largely on mudstone-sandstone ratios. The main purpose of the paper is to evaluate the validity of these models by documenting facies relationships and detailed bedding architecture of bar and channel deposits as well as mudstone-sandstone ratio within a compound incised-valley fill at the top of the Cretaceous Ferron Sandstone Member of the Mancos Shale Formation in the Henry Mountains region, Utah, U.S.A. Field photomosaics, walking out of beds, and 42 measured sections document the stratal and facies organization in the incised-valley fill. Two erosional surfaces...
The effects of downstream base-level control on fluvial architecture and geometry are well explored in several broadly similar sequence-stratigraphic models. Cretaceous Dakota Group strata, U.S. Western Interior, have characteristics reflecting combined downstream and upstream base-level controls that these models cannot address. Particularly, three layers of amalgamated channel-belt sandstone within this group thicken and are continuous for distances (? 300 km) along dip that stretch the reasonable lengths for which these models are intended to apply. As well, architecture in up-dip reaches records repeated valley-scale cut-and-fill cycles. This contrasts with equivalent strata down dip which record channel-scale...
The Castlegate Sandstone at its type section, Price Canyon, near Price, Utah, encompasses a single stratigraphic sequence spanning approximately 5 m.y. It includes a sandstone member corresponding to a lowstand systems tract, consisting of braided-fluvial sheet sandstones, and a mudstone member, in which shales are more abundant and some evidence of tidal influence is present. This is the transgressive to highstand systems tract. From near Trail Canyon eastward the mudstone member passes laterally into the Sego Sandstone and Neslen Formation, a succession of at least six higher-frequency sequences of fluvial-estuarine origin. The Buck Tongue, a marine shale unit separating the Castlegate Sandstone and the Sego Sandstone...
Paleocene crayfish burrows are present locally in great abundance in the Greater Green River, Hanna, Wind River, and Piceance basins of Wyoming and Colorado. In the Washakie sub-basin of the Greater Green River Basin, burrows are found in (1) lenticular, cross-bedded sandstones of fluvial-channel origin, (2) massive sandstones and mudrocks of floodplain origin that surround and interfinger with the cross-bedded sandstones, and (3) thin, sandy ironstone beds of overbank and crevasse-splay origin. The burrows, which represent crayfish activity in proximal to distal floodplain settings, are assigned to Camborygma symplokonomos, C. eumekenomos, and C. litonomos on the basis of their architectural morphologies. C. araioklados...
Even though paleoloess (loessite) deposits serve as important stratigraphic markers and can imply specific environmental and/or climatic conditions, few have been described in detail. The Mahogany Member of the Triassic Ankareh Formation of north-central Utah contains a well exposed example of an ancient loess, Although difficult to trace regionally, its distinguishing characteristics are uniform massiveness (lacking visible internal structure or bedding) over a 37 m thickness and a silt grain-size distribution. The upper 2.6 m of the loessite contains a distinct, vertical color zonation with lithologic changes indicating development of an immature paleosol, Whole-rock chemical analyses indicate trends in carbonate...
A new approach is recommended for estimating the catchment size and paleohydrology of ancient rivers from analysis of their sedimentary record. Estimates of drainage area have significant predictive value across a broad spectrum of geological applications, though attempts to derive them are remarkably uncommon. Previous sedimentological studies have relied on discharge-area relationships created by amalgamating data from a wide range of hydro-physiographic catchment characteristics. This averaging can lead to large errors in drainage-area calculations. Geomorphologists and engineers have been developing an extensive database of relationships between drainage area and channel dimensions or discharge that account...
In the middle Green River Formation of central Nine Mile Canyon, Uinta Basin, Utah, several lacustrine-dominated intervals [~]10 m thick comprise aggradational carbonate parasequence sets and a progradational clastic parasequence. Maximum flooding surfaces are best identified within profundal oil shale that caps some of the clastic parasequences. These lacustrine transgressive systems tracts therefore exhibit parasequence stacking patterns unlike typical marine sequences. Two types of sequence boundary are identified. Type A sequence boundaries display evidence for a basinward shift in facies across a regionally mappable surface that is an angular or, rarely, parallel unconformity, and they typically juxtapose amalgamated...
Isolated sandstone bodies encased in marine mudstones have proved difficult to explain, especially those that are not easily incorporated into conventional facies models. The Hatch Mesa succession (Campanian, lower Kenilworth Member) is a marine mudstone-encased, turbiditic sandstone body, 6 to 20 m thick, that is exposed along a 7-km-long outcrop belt, approximately 15 km east of Green River, Utah, U.S.A. Various interpretations of depositional environment and regional correlation have been proposed over the past 20 years. A sedimentological analysis of the Hatch Mesa succession suggests deposition as a storm-influenced, prodelta turbidite complex on the shallow inner shelf, between fair-weather and storm wave...
Thin (< 30-cm-thick) sets of eolian cross-strata with irregular upper bounding surfaces make up 27% of the Lower Jurassic Wingate Sandstone near Moab in southeastern Utah and up to 40% of the Middle Jurassic Entrada Sandstone near Dinosaur National Monument in northeastern Utah. Deformation structures, interpreted as the tracks of large reptiles, are common in windripple laminae within and directly adjacent to these sets. Lithosomes composed primarily of these sets range from < 1 m to 9 m in thickness. Cosets composed of thick, trough cross-stratified sets that are interbedded with cosets composed of the thinner sets contain smooth, nearly horizontal bounding surfaces. The lack of intertonguing with thick sets of...
Lakes tend to respond noticeably to minor changes in sediment and water balance driven by climatic, tectonic, or geomorphic processes. This unique behavior of lacustrine basins can provide a high-resolution record of geologic processes within the continental setting, far from the globally averaged record of marine strata. The Wilkins Peak Member of the Eocene Green River Formation, in Wyoming, USA, is dominated by aggradation of repetitive sedimentary facies successions recording distinct lacustrine expansions and contractions. These lacustrine "cycles" consist of up to four successive facies associations: littoral, profundal-sublittoral, palustrine, and salt pan. Because they comprise disparate facies that may...
Deposition of lacustrine sediments in the greater Green River Basin was progressively terminated in the middle Eocene as volcaniclastic detritus prograded across the basin; the lacustrine sediment of the Laney Member was replaced by deposition of the deltaic and fluvial sediments of the volcaniclastic Bridger and Washakie formations and the Sand Butte Bed of the Laney Member. The transition from the deposition of lacustrine to alluvial sediment also records a reversal in the direction of drainage across the basin that occurred between 49.5 Ma and 48.9 Ma. Prior to this transition, drainage entered the basin from the east and the arkosic detritus of the Cathedral Bluffs Member of the Wasatch Formation was deposited...
The Castlegate Sandstone is part of the Upper Cretaceous (Campanian-Maastrichtian) Mesaverde Group, a clastic wedge that prograded eastward from the Sevier Orogen of central Utah across the Western Interior Basin. The unit comprises the lowstand part of a regional fourth-order stratigraphic sequence. Earlier studies showed that the Castlegate Sandstone was deposited by braided rivers that deepened downstream from Price to east of Green River. Outcrop mapping employing photomosaics to document facies architecture, bounding surfaces, and paleocurrent information has been used to reconstruct the geometry of bars (macroforms) and bar complexes in the Castlegate rivers. The most common bar types are those that accreted...
The Upper Cretaceous Frontier Formation on the Moxa Arch in the western Green River Basin, Wyoming, has had a varied diagenetic history that was controlled in part by differences in composition of detrital framework grains and in burial history. Petrographic examination of 247 thin sections from 13 cores from the south-plunging arch and adjacent deep basin is the basis for diagenetic investigation of sandstones ranging in depth from 2 km to almost 5 km. Major diagenetic events were (1) mechanical compaction by grain rearrangement and deformation of ductile grains, (2) formation of illite and mixed-layer illite-smectite rims, (3) precipitation of quartz overgrowths, (4) precipitation of calcite cement, (5) generation...
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