Lower Green River Research Articles

Environmental and microbial influence on chemistry and dolomite formation in an ancient lake, Green River Formation (Eocene), Uinta basin, Utah, U.S.A.

ABSTRACT Integrated stratigraphic, petrographic, and geochemical data allow interpretation of biogeochemical and mineralization processes in paleoenvironmental context of ancient lacustrine environments. These indicate that lake chemistry, microbial processes, and organic matter (OM) strongly influenced dolomite formation in near-surface environments throughout deposition of the Green River Formation (Eocene, Uinta basin, Utah). The lower Green River Formation consists of interbedded fluvio-deltaic siliciclastics, paleosols, carbonate mud, coated-grain carbonates, mollusk and ostracod limestones, and microbialites all landward of profundal OM-bearing illitic mudrocks. Calcite, dolomite, Fe-dolomite, and authigenic feldspars are common. Carbonate δ18O and δ13C are covariant, and positive excursions of carbonate δ13C (up to 6.9‰ VPDB) and organic-matter δ15N (up to 13.9‰ V-AIR) occur in profundal OM-bearing mudrocks. The upper Green River Formation consists mainly of laminated OM-lean and OM-rich dolomitic muds (i.e., “oil-shales”). Zoned dolomite crystals with Mg-calcite centers and Fe-dolomite rims are widespread in addition to authigenic feldspars and Na-carbonates. Carbonate δ13C-enrichment (up to 15.8‰ VPDB), and organic-matter δ15N-enrichment (up to 18.4‰ V-AIR) occur in these OM-rich dolomite muds. Organic-matter δ13C is relatively invariable (mean = –29.3‰ VPDB) and does not covary with carbonate δ13C. Trends in mineralogy, organic-matter abundance, and stable isotopes result from changing hydrologic systems, paleoclimate, lake chemistry and microbial processes coincident with the Early Eocene Climate Optimum. The lower Green River Formation paleo-lake was smaller in area and volume, heavily influenced by meteoric fluvial input, variably oxygenated, and ranged from neutral and fresh to alkaline and saline. Especially in littoral environments with abundant microbialites, dolomite formed through recrystallization of precursor carbonate involving both replacement of precursor carbonate and direct precipitation as cements and overgrowths. The upper Green River Formation paleo-lake was more expansive with widespread low-oxygen, nutrient-rich, and alkaline saline environments with increased planktic organic-matter productivity. Microbial decay of organic matter in low-oxygen environments produced alkaline lake waters through methanogenesis, possible denitrification, and bacterial sulfate reduction to a limited degree. This favored precipitation of widespread dolomite, as well as Na-carbonates, authigenic feldspars, and analcime from lake water and phreatic pore water. Extracellular polymeric substances (EPS) excreted by microbial communities provided favorable nucleation sites for Mg-carbonate, allowing kinetic barriers of low-temperature dolomite formation to be overcome. Cycling of pH due to turnover of organic matter and associated microbial processes potentially bolstered EPS generation and abiotic environmental conditions favorable to dolomite precipitation. It is likely that metastable precursor carbonate was recrystallized to ordered dolomite, but it is possible that direct precipitation occurred. Fe-dolomite overgrowths precipitated after dolomite where microbial Fe reduction occurred in stagnant, oxygen-depleted, alkaline pore waters.

Using pore system characterization to subdivide the burgeoning Uteland Butte Play, Green River Formation, Uinta Basin, Utah

Over 240 horizontal wells with highly variable production results have been drilled in the Uteland Butte member (UBm) of the lower Green River Formation in the Uinta Basin, Utah. The best wells have each produced more than 300,000 barrels of oil in the first 12 months of production, with conservative Estimated Ultimate Recoveries (EURs) for several wells above a million barrels. Conversely, the poorest UBm wells have initial production rates of less than 10,000 barrels of oil in the first year and will never recoup their drilling costs. Pore pressure, oil viscosity, well length, and well completion are recognized as important controls on well productivity. Less understood, but of equal importance, is the variability in reservoir types across the UBm play. The UBm can be divided into sub-plays by district using the dominant pore systems in each area. We defined four distinct sub-plays within the Uinta Basin: 1) intergranular-dominated porosity, 2) intercrystalline- pore-dominated dolomite, 3) mixed intercrystalline-organic porosity, and 4) organic porosity. Reservoirs in the intergranular-dominated porosity sub-play are mostly present in the form of nearshore siliciclastic and carbonate bars, such as ooid and ostracod shoals, fluvial mouth bars, and nearshore siliciclastic bars. The normal pressure and charge in these reservoirs are due to hydrocarbon migration out of the deeper basin. Source rocks in this sub-play have an average maturity of 0.5 to 0.7 vitrinite reflectance (VRo), too low for mainstage oil generation for these lacustrine shales (Ruble and others, 2001), and produce highly viscous black wax with very low gas-to-oil ratios (GORs). To date, horizontal wells drilled in this sub-play have not been economically successful. The intercrystalline-pore-dominated sub-play consists of thin (<2 to 8+ feet), laterally continuous, high-porosity dolomites that act as the best reservoirs. The reservoir is normally to slightly overpressured and is predominately charged with hydrocarbons that migrated out of the deeper basin. This sub-play was the first to be drilled horizontally, with the dolomite beds being identified as the highest quality targets. The UBm is thick in the intercrystalline-pore-dominated fairway, consisting of over 130 feet of carbonates and black shales, with only a fraction of the interval being high-porosity dolomites. This sub-play has an average VRo of 0.6 to 0.8, still too low for mainstage oil generation in these rocks and produces a migrated black wax with low GORs. The mixed intercrystalline-organic porosity sub-play is largely self-sourced and significantly overpressured. This sub-play has the thickest gross section and is dominated by thin dolomite beds, thicker argillaceous limestones, and thicker shaley beds, with the latter units contributing significant production. Maturities in this sub-play range from 0.8 to 1.0 VRo. This sub-play produces a yellow to gray wax with moderate GORs. Finally, the organic-porosity-dominated sub-play is highly overpressured and completely self-sourced. There is relatively little reservoir-quality dolomite, the limestones are more argillaceous, and the organic-rich carbonate shales are thicker. The productive reservoir in this sub-play consists of organic porosity largely contained in bitumen that has been expelled at lower maturity, then continued to thermally degrade with higher maturity, converting to zones of interconnected organic porosity. Maturities range from 1.0 to 1.2 VRo and the hydrocarbons produced are a bright yellow wax with relatively high GORs. To be economically developed, each of these sub-plays requires individually tailored drilling, completion, and production strategies. By recognizing the important differences these pore systems exert on best development practices and then accurately mapping them across the basin, operators, interest owners, and regulatory agencies can more efficiently plan operations.

Channel narrowing by inset floodplain formation of the lower Green River in the Canyonlands region, Utah

AbstractThe lower Green River episodically narrowed between the mid-1930s and present day through deposition of new floodplains within a wider channel that had been established and/or maintained during the early twentieth century pluvial period. Comparison of air photos spanning a 74-yr period (1940–2014) and covering a 61 km study area shows that the channel narrowed by 12% from 138 ± 3.4 m to 122 ± 2.1 m. Stratigraphic and sedimentologic analysis and tree ring dating of a floodplain trench corroborates the air photo analysis and suggests that the initial phase of floodplain formation began by the mid-1930s, approximately the same time that the flow regime decreased in total annual and peak annual flow. Tamarisk, a nonnative shrub, began to establish in the 1930s as well. Narrowing from the 1940s to the mid-1980s was insignificant, because floodplain formation was approximately matched by bank erosion. Air photo analysis demonstrates that the most significant episode of narrowing was underway by the late 1980s, and analysis of the trench shows that floodplain formation had begun in the mid-1980s during a multi-year period of low peak annual flow. Air photo analysis shows that mean channel width decreased by ∼7% between 1993 and 2009. A new phase of narrowing may have begun in 2003, based on evidence in the trench. Comparison of field surveys made in 1998 and 2015 in an 8.5 km reach near Fort Bottom suggests that narrowing continues and demonstrates that new floodplain formation has been a very small proportion of the total annual fine sediment flux of the Green River. Vertical accretion of new floodplains near Fort Bottom averaged 2.4 m between 1998 and 2015 but only accounted for ∼1.5% of the estimated fine sediment flux during that period. Flood control by Flaming Gorge Dam after 1962 significantly influenced flow regime, reducing the magnitude of the annual snowmelt flood and increasing the magnitude of base flows. Though narrowing was initiated by changes in flow regime, native and nonnative riparian vegetation promoted floodplain formation and channel narrowing especially through establishment on channel bars and incipient floodplains during years of small annual floods.

Paleoflood hydrology on the lower Green River, upper Colorado River Basin, USA: An example of a naturalist approach to flood-risk analysis

Through a comprehensive paleoflood hydrological investigation we document natural evidence for at least 27 high-magnitude paleofloods at six sites on the Lower Green River, Utah. Hydraulic analysis, using the Sedimentation and River Hydraulic-2D model (SRH-2D), shows that the responsible peak paleoflood discharges ranged between 500 and 7500 m3/s. At least 14 of these paleoflood discharge peaks exceed a level twice that of the maximum systematic record of gauged flows: 1929 m3/s. Geochronological analyses, employing optically stimulated luminescence (OSL) and radiocarbon dating techniques, demonstrate that these 14 largest paleoflood peaks occurred during the past 700 years. Integration of the paleoflood data into flood frequency analyses (FFA) reveals considerably higher values for the upper tails of the flood distribution than does a FFA based solely on the systematic gauged record, indicating that extreme floods are larger and more frequent than implied by the relatively short gauged record. Through examination of three approaches to extreme flood estimation – conventional FFA, probable maximum flood estimation (PMF), and paleoflood hydrology (PFH) – we show the significance of the natural evidence for advancing scientific understanding of extreme floods that naturally occur in the Colorado River system. We argue that this kind of scientific understanding is absolutely essential for achieving a credible evaluation of extreme flood risk in a watershed of immense importance to economic prosperity of the southwestern U.S.

Forage Kochia and Russian Wildrye Potential for Rehabilitating Gardner’s Saltbush Ecosystems Degraded by Halogeton

Gardner’s saltbush ecosystems are increasingly being invaded by halogeton (Halogeton glomeratus [M. Bieb.] C.A. Mey.), an annual halophyte that increases soil surface salinity and reduces plant biodiversity. Thus, a study was established in the Flaming Gorge National Recreation Area within the lower Green River Basin of Wyoming to evaluate the potential for rehabilitating halogeton-dominated Gardner’s saltbush ecosystems with forage kochia (Bassia prostrata [L.] A.J. Scott), Russian wildrye (Psathyrostachys juncea [Fisch.] Nevski), tall wheatgrass (Thinopyrum ponticum [Podp.] Z.-W. Liu & R.-C. Wang), Indian ricegrass (Achnatherum hymenoides [Roem. & Schult.] Barkworth), and Gardner’s saltbush (Atriplex garneri [Moq.] D. Dietr.). A seeding evaluation, with and without prior disking, was conducted to determine ability of these species to establish. A transplant evaluation determined the effect of established plants on halogeton frequency at four 10-cm intervals (10–20, 20–30, 30–40, and 40–50 cm) distal from transplants. Gardner’s saltbush, tall wheatgrass, and Indian ricegrass did not establish in the seeded study or persist beyond the first year in transplant study. In contrast, Russian wildrye and forage kochia established and persisted, with Russian wildrye establishment higher (P = 0.05) in the disked treatment compared with no-till (4.5 and 1.7 plants m−2, respectively) and no-till favoring (P = 0.05) forage kochia establishment (2.3 and 0.8 plants m−2, respectively). Transplants of these two species reduced halogeton frequency by 52% relative to the control. Moreover, this interference of halogeton establishment by Russian wildrye and forage kochia had extended to 50 cm distal from transplant by the second year of the study. By the third year (2014), transplant survival and halogeton frequency were highly correlated (r = −0.61, P = 0.0001), indicating the importance of plant persistence. Results indicate that Russian wildrye and forage kochia can establish and reduce halogeton frequency, thereby providing an opportunity for rehabilitation of halogeton-invaded areas.

High-Resolution Stratigraphy of the lower portion of the Green River Formation at Raven Ridge and Red Wash Field, NE Uinta Basin, Utah, Colorado, USA: Facies and Stratigraphic Patterns in a High-Gradient, High-Energy Lacustrine System

Lacustrine strata of a portion of the Green River Formation studied in outcrops along Raven Ridge and in the subsurface around Red Wash Field in the northeastern Uinta Basin represent cyclic storm-dominated shoreface to deep lake deposition within a syntectonic embayment on the margin of Eocene Lake Uinta. The study interval consists of the lower Green River Formation, including the Douglas Creek, Garden Gulch, and lower Parachute Creek members, from the top of the underlying Wasatch to the Mahogany Zone of the Parachute Creek Member. Data consists of 11,900 ft (3627 m) of section measured at 23 locations across Raven Ridge, including 7,800 ft (2377 m) of hand-held gamma-ray scintillometer measurements, and over 500 wells in the greater Red Wash Field area, including pay zone analysis correlated to stratigraphy in the field. Facies analysis, as the basis for an integrated stratigraphic approach, reveals a seven-fold hierarchy of stratigraphic cycles ranging from two orders of large-scale cycles to five orders of progressively higher-frequency (smaller scale) shoreface-lake cycles across an 18-mile (29 km) long and 1900-ft (579 m) thick dip-oriented stratigraphic transect. This study recognized twenty-two facies grouped into eight facies tracts using Walther’s Law for two composite shoreface successions: one for a siliciclastic storm-graded shoreface profile that was dominant during times of regression and one for a carbonate profile that dominated in times of transgression. Two important regional facies trends across Raven Ridge include: 1) greater proportions of mudstone facies present in the southern, upper portion of the Green River Formation; and 2) significantly higher proportion of bioturbated sandstone in the northern, lower portion of the formation. The long-term 2nd-order transgression of Lake Uinta from base to top of the study interval results in an evolution from a low-gradient shoreline with marshes, ponds, and sand/mud flats to a high-gradient high-energy profile composed of spits and shorefaces that grew southward away from the emergent highlands. A composite storm-graded shelf profile shows how trough, hummocky, and swaley cross stratification type and amalgamation style change offshore proportionally to contain mud-dominated tempestites, erosional storm furrows, and oil shale. In the most offshore positions, diastasis cracks caused by differential loading are common. The lacustrine shoreface profile is compressed in the Green River Fm. in the study area with narrow facies tracts and large local gradient changes as a result of different responses to sediment supply. As a lake grows and shorelines migrate, the increase in accommodation is balanced, or in-phase, by a corresponding increase in sediment supply resulting in shoreface progradation keeping up with lake-level rise. As the shoreface stacks vertically during the rise, over steepening and failure of the profile generates gravity-flow sandstone facies. Little reworking of hummocky cross stratification high on the profile was observed, probably because wave power was limited by a shallow fair-weather wave-base. These differences also result in more symmetrical lacustrine shoreface cycles, with a large proportion of sediment partitioned into rise hemicycles, as opposed to the classical fall-asymmetric marine para-sequence which tends to have little to no strata preserved in the rise hemicycle along most of the shoreface profile. Landward-stepping lacustrine shoreface cycles are more common during the early rise portions of larger-scale 3rd-order megacycles for similar reasons. Strata at Raven Ridge support the concept that Eocene Lake Uinta was chemically stratified, or meromictic, at least during certain periods. The equable subtropical Eocene paleoclimate is interpreted to be the most important control on meromixis. Chemical stratification played a critical role in the development and preservation of organic matter, as evidenced by oil shale facies. The equable climate, however, might also have made the lake prone to thermal stratification. A paradox exists in the storm dominance of the lacustrine shorefaces and the coeval lake stratification: wave energy apparently was insufficient to break through the strong chemocline. Red Wash Field, directly downdip from the Raven Ridge outcrop belt, is an example of an oil field in a setting where the lake margin is not coincident with a structural feature: a “non-coincident” margin. Reservoirs mostly are present in the 6th-order aggradational shoreface cycles that are interpreted to have accumulated in the rise portions of 3rd-order megacycles. The best reservoir facies are trough, hummocky, and swaley cross-stratified sandstone deposited by storm processes and structureless sandstone probably derived from over steepening and failure of the shoreface during transgression. A petroleum accumulation model encompassing the Red Wash-Raven Ridge area proposes that lacustrine-sourced petroleum originated from an over-pressured mature cell in the Altamont-Bluebell field region. Oil migrated updip through leaky seals and became trapped in reservoirs within the non-coincident lake margin strata. An irregular shoreline configuration and compaction folds at Red Wash Field trapped petroleum. After reaching spill point at Red Wash Field, oil migrated farther updip to Raven Ridge and Asphalt Ridge, forming tar sand accumulations.

Effects of Moderate and Extreme Flow Regulation on Populus Growth along the Green and Yampa Rivers, Colorado and Utah

AbstractRiver regulation induces immediate and chronic changes to floodplain ecosystems. We analysed both short‐term and prolonged effects of river regulation on the growth patterns of the keystone riparian tree species Fremont cottonwood (Populus deltoides ssp. wislizenii) at three upper Colorado River Basin rivers having different magnitudes of flow regulation. We compared cottonwood basal area increment on (i) the regulated Upper Green River below Flaming Gorge Dam; (ii) the adjacent free‐flowing Yampa River; and (iii) the partially regulated Lower Green River below their confluence. Our goal was to identify the hydrologic and climatic variables most influential to tree growth under different flow regimes. A dendrochronological analysis of 182 trees revealed a long‐term (37 years) trend of declining growth during the post‐dam period on the Upper Green, but trees on the partially regulated Lower Green maintained growth rates similar to those on the reference Yampa River. Mean annual, mean growing season, and peak annual discharges were the multicollinear flow variables most correlated to growth during both pre‐dam and post‐dam periods at all sites. Annual precipitation was also highly correlated with tree growth, but precipitation occurring during the growing season was poorly correlated with tree growth, even under full river regulation conditions. This indicates that cottonwoods rely primarily on groundwater recharged by river flows. Our results illustrate the complex and prolonged effects of flow regulation on floodplain forests, and suggest that flow regulation designed to simulate specific aspects of flow regimes, particularly peak flows, may promote the persistence of these ecosystems. Copyright © 2016 John Wiley & Sons, Ltd.

Stratigraphic Architecture of a Fluvial-lacustrine Basin-fill Succession at Desolation Canyon, Uinta Basin, Utah: Reference to Walthers’ Law and Implications for the Petroleum Industry

A continuous window into the fluvial-lacustrine basin-fill succession of the Uinta Basin is exposed along a 48-mile (77-kilometer) transect up the modern Green River from Three Fords to Sand Wash in Desolation Canyon, Utah. In ascending order the stratigraphic units are: 1) Flagstaff Limestone, 2) lower Wasatch member of the Wasatch Formation, 3) middle Wasatch member of the Wasatch Formation, 4) upper Wasatch member of the Wasatch Formation, 5) Uteland Butte member of the lower Green River Formation, 6) lower Green River Formation, 7) Renegade Tongue of the lower Green River Formation, 8) middle Green River Formation, and 9) the Mahogany oil shale zone marking the boundary between the middle and upper Green River Formations. This article uses regional field mapping, geologic maps, photographs, and descriptions of the stratigraphic unit including: 1) bounding surfaces, 2) key upward stratigraphic characteristics within the unit, and 3) longitudinal changes along the river transect. This information is used to create a north-south cross section through the basin-fill succession and a detailed geologic map of Desolation Canyon. The cross section documents stratigraphic relationships previously unreported and contrasts with earlier interpretations in two ways: 1) abrupt upward shifts in the stratigraphy documented herein, contrast with the gradual interfingering relationships proposed by Ryder et al., (1976) and Fouch et al., (1994), 2) we document fluvial deposits of the lower and middle Wasatch to be distinct and more widespread than previously recognized. In addition, we document that the Uteland Butte member of the lower Green River Formation was deposited in a lacustrine environment in Desolation Canyon. Two large-scale (member-scale) upward patterns are noted: Waltherian, and non-Waltherian. The upward successions in Waltherian progressions record progradation or retrogradation of a linked fluvial-lacustrine system across the area; whereas the upward successions in non-Waltherian progressions record large-scale changes in the depositional system that are not related to progradation or retrogradation of the ancient lacustrine shoreline. Four Waltherian progressions are noted: 1) the Flagstaff Limestone to lower Wasatch Formation member records the upward transition from lacustrine to fluvial—or shallowing-upward succession; 2) the upper Wasatch to Uteland Butte records the upward transition from fluvial to lacustrine—or a deepening upward succession; 3) the Uteland Butte to Renegade Tongue records the upward transition from lacustrine to fluvial—a shallowing-upward succession; and 4) the Renegade Tongue to Mahogany oil shale interval records the upward transition from fluvial to lacustrine—a deepening upward succession. The two non-Waltherian progressions in the study area are: 1) the lower to middle Wasatch, which records the abrupt shift from low to high net-sand content fluvial system, and 2) the middle to upper Wasatch, which records the abrupt shift from high to intermediate net-sand content fluvial system.

“Branded by the Lincolnites as Guerrillas”: Adam Rankin Johnson, Guerrilla Identity, and Irregular Warfare in the Lower Green River Valley in 1862

“Branded by the Lincolnites as Guerrillas”: Adam Rankin Johnson, Guerrilla Identity, and Irregular Warfare in the Lower Green River Valley in 1862

Lacustrine depositional environments in the Green River Formation, Uinta Basin: Expression in outcrop and wireline logs

Lacustrine basins are key oil-productive areas of the world. Because fewer lacustrine exist than marine basins, lacustrine systems are relatively less well studied. This paper investigates fluvial-lacustrine depositional environments and their representation in wireline logs in the lower part of the Green River Formation, Uinta Basin, Utah. The five principal depositional environments of the lower Green River Formation are (1) deep lacustrine, (2) shallow lacustrine, (3) lacustrine delta, (4) coastal plain, and (5) alluvial plain. Deep-lake environments are characterized by laminated oil shales and fine-grained carbonates. These facies exhibit anomalously high neutron porosity, and low bulk density relative to other settings. Shallow-lake environments are dominated by weakly laminated to massive gray mudstones, and limestones, with occasional thin high-bulk-density sandstones. Lacustrine deltas (both sand-prone and mud-prone) grade from shallow-lake muds to ripple-laminated to cross-bedded sandstones. The upward decrease in clay can be seen in the gamma-ray, neutron-porosity, and bulk-density profiles of deltaic intervals. Coastal plain mudstones have a greenish hue, and frequently contain organic matter. Channels in coastal plain settings are typically thin, isolated, and heterolithic. Alluvial plain channels tend to be sandier, thicker, and less isolated than coastal plain channels. Alluvial mudstones are reddish with abundant pedogenic features. The vertical association of depositional environments in the lower Green River indicates both high-amplitude and high-frequency lake-level fluctuations. However, the macro-scale trend shows a rapid deepening of the lake lower in the section, followed by a gradual filling of the accommodation, and a gradual flooding near the top of the studied interval. The lower Green River depositional environments form key petroleum system components. Oil shales in the deep lacustrine settings are the major source rock, and coastal plain muds are a potential minor source. Regional seals are formed by deposits of tight lacustrine shale and carbonate deposited in both marginal and deep lacustrine settings. Delta, coastal plain, and alluvial plain sands form the principal reservoirs. Some deep lacustrine mudstones and carbonates are also potential unconventional reservoirs. Correlation of outcrop observations from well log expressions allows depositional environments to be interpreted in the Uinta Basin and other lacustrine basins.

From flood control to flood adaptation: a case study on the Lower Green River Valley and the City of Kent in King County, Washington

Despite massive investment in flood control infrastructure (FCI), neither cities nor rivers have been well served—flooding continues to challenge cities around the world, while riverine ecosystems are degraded by FCI. Although new flood hazard management concepts have shifted the focus away from FCI, many cities continue to count on FCI to prevent flood damage. It is assumed that existing built-up areas can only count on FCI, as large-scale retreat is often impossible. However, flood adaptation—retrofitting the built environment to prevent damage during flooding—as an option is often ignored. This paper argues against the continual use of FCI to prevent flood damage by reviewing FCI’s established problems. The paper examines human–river interactions associated with FCI, focusing on the feedback mechanisms in the interactions, with a case study on the Lower Green River (LGR) valley in King County, Washington, USA. An urban ecology research model is employed to organize the case study, where interactions between floodplain urbanization, FCI, flow and sediment changes, flood risk, and riverine ecosystem are explored and two feedback mechanisms—river adjustment and flood risk perception—are explicitly addressed. The resulting complex dynamics, in terms of cross–scale interactions, emergence, nonlinearity, and surprises, are synthesized and limitations of FCI outlined. Flood adaptation is explored as a plausible alternative to flood control to nurture flood resilience. A management scenario of flood adaptation for the City of Kent—the largest municipality in the LGR valley—is developed to discuss the implications of flood adaptation on flood risk and river restoration.

Amplifiers, filters and geomorphic responses to climate change in Kentucky rivers

Efforts to predict responses to climate change and to interpret modern or paleoclimate indicators are influenced by several levels of potential amplifiers, which increase or exaggerate climate impacts, and/or filters, which reduce or mute impacts. With respect to geomorphic responses and indicators, climate forcings are partly mediated by ecological, hydrological, and other processes which may amplify or filter impacts on surface processes and landforms. Then, geomorphic responses themselves may be threshold-dominated or dynamically unstable, producing disproportionately large and long-lived responses to climate changes or disturbances. Or, responses may be dynamically stable, whereby resistance or resilience of geomorphic systems minimizes the effects of changes. Thus a given geomorphic response to climate could represent (at least) two levels of amplification and/or filtering. An example is given for three fluvial systems in Kentucky, U.S.A, the Kentucky, Green, and Big South Fork Rivers. Climate impacts in the early Quaternary were amplified by glacially-driven reorganization of the ancestral Ohio River system to the North, and by dynamical instability in the down-cutting response of rivers incising plateau surfaces. Effects of more recent climate changes, however, have been filtered to varying extents. Using alluvial terraces as an example, the study rivers show distinctly different responses to climate forcings. The lower Green River has extensive, well-developed terraces recording several episodes of aggradation and downcutting, while the Big South Fork River has no alluvial terraces. The Kentucky River is intermediate, with limited preservation of relatively recent terraces. The differences can be explained in terms of differences among the rivers in (1) filtering effects of constraints on fluvial responses imposed by strongly incised, steep-walled bedrock controlled valleys; and (2) amplifier effects of periodic damming of lower river reaches by glaciofluvial outwash.

Population Status of Colorado Pikeminnow in the Green River Basin, Utah and Colorado

AbstractCapture‐recapture sampling of 819 km of streams in the Green River subbasin, Utah and Colorado, of the Colorado River basin was conducted in 2000‐2003 to estimate population demographic parameters and recovery status for endangered Colorado pikeminnow Ptychocheilus lucius. Parameter estimates from a Huggins robust‐design, multistratum model suggested a basinwide decline in the abundance of adult (total length, ≥450 mm) Colorado pikeminnow. Reductions were most severe in the middle Green River (59%) and White River (63%), the two largest population segments. Reductions were less severe in the Yampa River (29%), Desolation‐Gray Canyon (11%), and lower Green River reaches (36%). In 2001, the first year the entire subbasin was sampled, adult Colorado pikeminnow abundance was estimated at 3,304 fish (95% confidence interval, 2,900‐3,707) but declined to 2,142 fish (1,686‐2,598) by 2003, a 35% reduction. However, accounting for a reach not sampled in 2000 makes it likely that the reduction was 48% over the 2000‐2003 period. The abundance of recruits (400‐449 mm) in the study area averaged 8.9% of adult abundance. The annual survival rate for 2000‐2003 was 0.65 (0.59‐0.71), lower than the 0.82 rate estimated for 1991‐1999; mortality exceeded recruitment. The few captures and lack of recaptures of fish of at least 800 mm suggest that apparent survival was low for large Colorado pikeminnow. The reduced abundance of adult Colorado pikeminnow was due, in part, to the weak year‐classes of age‐0 fish produced in the 1990s and the reduced survival of recruits and adults in 2000‐2003. Based on these results, downlisting of this species is not warranted at this time. Better understanding of the factors that influence adult survival rates, abundance dynamics, and the recruitment of early life stages as well as the effects of flow recommendations and nonnative predaceous fishes would assist the conservation of Colorado pikeminnow.

Processes Of Tamarix Invasion And Floodplain Development Along The Lower Green River, Utah

Significant ecological, hydrologic, and geomorphic changes have occurred during the 20th century along many large floodplain rivers in the American Southwest. Native Populus forests have declined, while the exotic Eurasian shrub, Tamarix, has proliferated and now dominates most floodplain ecosystems. Photographs from late 19th and early 20th centuries illustrate wide river channels with largely bare in-channel landforms and shrubby higher channel margin floodplains. However, by the mid-20th century, floodplains supporting dense Tamarix stands had expanded, and river channels had narrowed. Along the lower Green River in eastern Utah, the causal mechanism of channel and floodplain changes remains ambiguous due to the confounding effects of climatically driven reductions in flood magnitude, river regulation by Flaming Gorge Dam, and Tamarix invasion. This study addressed whether Tamarix establishment and spread followed climate- or dam-induced reductions in annual peak flows or whether Tamarix was potentially a driver of floodplain changes. We aged 235 Tamarix and 57 Populus individuals, determined the hydrologic and geomorphic processes that controlled recruitment, identified the spatial relationships of germination sites within floodplain stratigraphic transects, and mapped woody riparian vegetation cohorts along three segments of the lower Green River. The oldest Tamarix established along several sampling reaches in 1938, and 1.50-2.25 m of alluvium has accreted above their germination surfaces. Nearly 90% of the Tamarix and Populus samples established during flood years that exceeded the 2.5-year recurrence interval. Recruitment was most common when large floods were followed by years with smaller peak flows. The majority of Tamarix establishment and Green River channel narrowing occurred long before river regulation by Flaming Gorge Dam. Tamarix initially colonized bare instream sand deposits (e.g., islands and bars), and most channel and floodplain changes followed the establishment of Tamarix. Our results suggest that Tamarix recruitment was triggered by large annual floods that were followed by years with lower peak flows, not by periods of low flow alone. Tamarix appears to have actively invaded floodplains, while Populus colonization has been limited. Thus, Tamarix invasion may have greatly influenced floodplain development and riparian vegetation composition along the lower Green River since the early 20th century.

Evaluation of soluble benzene migration in the Uinta Basin

AbstractField sampling and mathematical modeling are used to study the long‐distance transport and attenuation of petroleum‐derived benzene in the Uinta Basin, Utah. Benzene concentration was measured from oil and oil field formation waters of the Altamont‐Bluebell and Pariette Bench oil fields in the basin. It was also measured from springs located in the regional groundwater discharge areas, hydraulically down‐gradient from the oil fields sampled. The average benzene concentration in oils and co‐produced waters is 1946 and 4.9 ppm at the Altamont‐Bluebell field and 1533 and 0.6 ppm at the Pariette Bench field, respectively. Benzene concentration is below the detection limit in all springs sampled. Mathematical models are constructed along a north–south trending transect across the basin through both fields. The models represent groundwater flow, heat transfer and advective/dispersive benzene transport in the basin, as well as benzene diffusion within the oil reservoirs. The coupled groundwater flow and heat transfer model is calibrated using available thermal and hydrologic data. We were able to reproduce the observed excess fluid pressure within the lower Green River Formation and the observed convective temperature anomalies across the northern basin. Using the computed best‐fit flow and temperature, the coupled transport model simulates water washing of benzene from the oil reservoirs. Without the effect of benzene attenuation, dissolved benzene reaches the regional groundwater discharge areas in measurable concentration (>0.01 ppm); with attenuation, benzene concentration diminishes to below the detection limit within 1–4 km from the reservoirs. Attenuation also controls the amount of water washing over time. In general, models that represent benzene attenuation in the basin produce results more consistent with field observations.

Abstract: Sequence stratigraphy and reservoir character of lacustrine carbonates in the Basal Limestone Member: Lower Green River formation (Eocene), Duchesne and Antelope Creek Fields, Duchesne Co., Utah

Abstract: Sequence stratigraphy and reservoir character of lacustrine carbonates in the Basal Limestone Member: Lower Green River formation (Eocene), Duchesne and Antelope Creek Fields, Duchesne Co., Utah

Abstract: The Castle Peak Member of the lower Green River Formation, Antelope Creek Field, Duchesne Co., Utah: An example of the effects of a migrating shoreline on the expression of an open-lacustrine carbonate facies

Abstract: The Castle Peak Member of the lower Green River Formation, Antelope Creek Field, Duchesne Co., Utah: An example of the effects of a migrating shoreline on the expression of an open-lacustrine carbonate facies

Factors controlling the establishment of Fremont cottonwood seedlings on the Upper Green River, USA

Declines in cottonwood (Populus spp.) recruitment along alluvial reaches of large rivers in arid regions of the western United States have been attributed to modified flow regimes, lack of suitable substrate, insufficient seed rain, and increased interspecific competition. We evaluated whether and how these factors were operating during 1993–1996 to influence demographics of Fremont cottonwood (P. deltoides Marshall subsp. wislizenii (Watson) Eckenwalder) along reaches of the Green and Yampa Rivers near their confluence in northwestern Colorado. We examined seedling establishment, defined as survival through three growing seasons, at three alluvial reaches that differed primarily in the level of flow regulation: a site on the unregulated Yampa, an upper Green River site regulated by Flaming Gorge Dam, and a lower Green River site below the Green–Yampa confluence. Seed rain was abundant in all sites, and led to large numbers of germinants (first-year seedlings) appearing each year at all sites. The regulated flow in the upper Green River reach restricted germination to islands and cut banks that were later inundated or eroded; no seedlings survived there. Mortality at the lower Green River site was due largely to desiccation or substrate erosion; 23% of 1993 germinants survived their first growing season, but at most 2% survived through their second. At the Yampa River site, germinants appeared on vegetated and unvegetated surfaces up to 2.5 m above base flow stage, but survived to autumn only on bare surfaces at least 1.25 m above base flow stage, and where at least 10 of the upper 40 cm of the alluvium was fine-textured. Our studies of rooting depths and the stable isotopic composition of xylem water showed that seedlings in the most favorable locations for establishment at the Yampa site do not become phreatophytic until their third or fourth growing season. Further, the results of experimental field studies examining effects of shade and competition supported the hypothesis that insufficient soil moisture, possibly in combination with insufficient light, restricts establishment to unvegetated sites. Collectively, the demographic and experimental studies suggest that, in arid regions, soil water availability is at least as important as light level in limiting establishment of Fremont cottonwood seedlings. We hypothesize that in cases where arid land rivers experience large spring stage changes, recruitment is further constrained within bare areas to those sites that contain sufficient fine-textured alluvium, saturated during the spring flood, to provide the flood-derived soil moisture normally necessary for late-summer seedling survival. Copyright © 1999 John Wiley & Sons, Ltd.

Clearing Up Clouded Waters: Palaeoenvironmental Analysis of Freshwater Mussel Assemblages from the Green River Shell Middens, Western Kentucky

Despite much progress in the analysis of Middle and Late Archaic Period (c. 6000–3000bp) shell midden sites along the lower Green River, many issues remain unresolved. One area of concern is the relationship between malacological and geoarchaeological data. Specifically, archaeological mussel assemblages have been interpreted to suggest shallow, swiftly flowing sections of river near the sites, whereas geoarchaeological discussions have been interpreted to indicate a deep, sluggish channel. This apparent contradiction has contributed to discussions that question the traditionally presumed dietary role of the shellfish, positing instead, for example, that shell could have been transported long distances in order to construct mortuary monuments. In this paper we show that the notion of a contradiction between malacological and geoarchaeological data is false. On the one hand, an analysis of mussels from the Haynes site (15BT11) supports a previous reconstruction of stream conditions based on malacological data from the nearby Carlston Annis site (15BT5). On the other hand, geoarchaeological discussions have been misconstrued through literal interpretation of generalizations that apply at a broad, geological scale. Supporting data, especially from pre-impoundment survey maps, suggest that the stretches of river in question included suitable habitat for the mussel species that dominate the middens. With this point of confusion resolved, we plan subsequent research to expand the data base at Haynes and other shell-bearing sites, focusing on overall palaeoenvironmental reconstruction, taphonomic processes, site distributions in relation to geomorphological contexts, and dietary analysis.

Abstract: High-Resolution Stratigraphy of the Lower Green River Formation at Raven Ridge and Red Wash Field, NE Uinta Basin: Stratigraphic Control on Petroleum Subsystems

Abstract: High-Resolution Stratigraphy of the Lower Green River Formation at Raven Ridge and Red Wash Field, NE Uinta Basin: Stratigraphic Control on Petroleum Subsystems