Southeastern Uinta Basin Research Articles

Highly Seasonal and Perennial Fluvial Facies: Implications For Climatic Control On the Douglas Creek and Parachute Creek Members, Green River Formation, Southeastern Uinta Basin, Utah, U.S.A.

Abstract: The early to middle Eocene Green River Formation consists of continental strata deposited in Laramide ponded basins in Utah, Colorado, and Wyoming. This study (1) documents fluvial and lacustrine strata from the Douglas Creek and Parachute Creek members of the middle Green River Formation, southeastern Uinta Basin, Utah, and (2) uses new interpretations of the link between climate and fluvial sedimentary expression to interpret the terrestrial evolution of early Eocene climate. The stratigraphy was analyzed via outcrops along a 10 km transect in Main Canyon on the Tavaputs Plateau, and is divided into three distinct, stratigraphically separated depositional settings: (1) the lowermost Interval 1 is dominated by amalgamated sandstone channels that contain 70–100% upper-flow-regime sedimentary structures. The channels are interpreted to represent fluvial deposits controlled by a highly seasonal climate, where most deposition was limited to seasonal flooding events. (2) Interval 2 is dominated by alternating siliciclastic and carbonate lacustrine deposits, interpreted as local pulsed fluvial siliciclastic input into shallow Lake Uinta, and periods of fluvial quiescence represented by littoral carbonate deposition. (3) The uppermost Interval 3 is dominated by erosionally-based, trough cross bedded sandstone channels interbedded with littoral lacustrine and deltaic deposits. The Interval 3 sandstone channels are interpreted as perennial fluvial deposits with relatively little variation in annual discharge, akin to modern humid-temperate fluvial systems. The stratigraphic transition from seasonally controlled (Interval 1) to perennial (Interval 3) fluvial deposits is interpreted to represent a fundamental shift in Eocene climate, from the peak hyperthermal regime of the Early Eocene Climatic Optimum (EECO) to a more stable post-EECO climate.

Results of Detailed Mapping in the Northern Paradox Basin and Southeastern Uinta Basin Energy and Metal Resource Area, Grand and Uintah Counties, Utah

Results of Detailed Mapping in the Northern Paradox Basin and Southeastern Uinta Basin Energy and Metal Resource Area, Grand and Uintah Counties, Utah

Unconformity-Bounded Paleocene Conglomerate Sequence, Southeastern Uinta Basin: ABSTRACT

Unconformity-Bounded Paleocene Conglomerate Sequence, Southeastern Uinta Basin: ABSTRACT

A baseline geochemical description of surficial materials in the southeastern Uinta Basin, Utah

A geochemical baseline survey was conducted in the oil shale region of the Uinta Basin, Utah, to describe the trace element composition of surface soils, stream sediments, and selected plant species Sampling was conducted using nested, hierarchical designs The baseline description was constructed, in part, with analysis of variance techniques Baseline data for B, F, Mo, and Cu are presented because of their potential environmental sensitivity Baseline concentrations of these four elements are elevated above an average soil and an average plant ash, but are similar to geochemical baselines constructed in the Piceance Creek Basin, Colorado Surface soil Mo, B, and F, stream sediment Mo, and F in Big sagebrush exhibit reproducible geographic variation on the basis of this sampling

Bituminous Sandstone Resource Evaluation of PR Spring Deposit, Uintah and Grand Counties, Utah: ABSTRACT

The Laramie Energy Technology Center (LETC), Department of Energy, completed a seven-corehole drilling program in 1980 at the PR Spring tar sand deposit, southeastern Uinta Basin, Utah. The core data from these locations were integrated with data from 70 other locations to update the following deposit characteristics: vertical and aerial extent, stratigraphy, and rock properties. Oil-impregnated sandstones are found as surface outcrops and to depths of 475 ft (145 m). Three main tar sand zones in the Douglas Creek Member of the Eocene Green River Formation were correlated across the deposit. Up to 27 separate tar sand beds were identified across the deposit, ranging from 1-35 ft (0.5-11 m) thick. These saturated zones and beds are lenticular and discontinuous, both vertic lly and horizontally. Analytical results from 6 of the LETC cores and 32 other cores were interpreted to further evaluate the deposit. Computer-generated isopleth maps identified the following general trends: the thickest zones are found in the south-central portion of the deposit; extracted permeability and extracted porosity decrease downdip (northwest); oil saturation decreases to the west-southwest; and water saturation decreases to the east. End_of_Article - Last_Page 528------------

Influence of Diagenetic Reactions on Nonmarine Upper Cretaceous Rocks of Southman Canyon Gas Field, Uinta Basin, Utah: ABSTRACT

End_Page 832------------------------------Natural gas is produced from sandstone in the Upper Cretaceous Neslen, Farrer, and Tuscher Formations in the southeastern Uinta basin. Examination of these sandstone units along the eastern Book Cliffs indicates that most of the reservoir units are part of alluvial channels. Sandstone beds in the Neslen represent relatively small and isolated meandering channels in swampy coastal plains. Sandstone beds in the Farrer were deposited by somewhat larger and more numerous meandering streams depositionally upslope from the Neslen setting. The Tuscher Formation represents the most landward facies and was deposited principally by meandering, laterally migrating, large streams with local braided courses. Core samples from the Southman Canyon gas field studied with the scanning electron microscope (SEM) indicate that extensive diagenetic modifications of the reservoir rocks have occurred and have strongly influenced reservoir characteristics. Authigenic overgrowths on detrital quartz are common, but secondary silica is not a significant cementing agent. Feldspars are not abundant and are commonly altered to illitic clay. Carbonate minerals--dolomite, ankerite, calcite, and minor siderite--account for up to 20% of the rock. They are generally interstitial and have replaced some detrital quartz and rock fragments. Chert and other rock fragments account for more than 20% of the volume of many sandstones. Some rock fragments are extensively altered by mechanical deformation, dissolution, and clay-mineral formation. Dissolution and leaching, primarily of rock fragments, have improved the reservoir storage capacity of the sandstone units by producing a significant amount of intergranular and intragranular secondary porosity. The dissolution and leaching appear to have exerted a greater influence on reservoir characteristics than did mechanical deformation and growth of authigenic minerals. Most porosity in the units is of secondary origin. End_of_Article - Last_Page 833------------

Oil-Impregnated Lacustrine and Fluvial Sandstone in Green River Formation (Eocene), Southeastern Uinta Basin, Utah: ABSTRACT

Oil-impregnated sandstone, in units up to 75 ft thick, are present in the lower Green River Formation in the P.R. Spring area, southeastern Uinta basin. Reserve estimates indicate that there may be about 3.7 billion bbl in place. A total of 308 paleocurrent measurements were made at 13 localities in the upper Wasatch Formation (Paleocene-Eocene) and the lower Green River Formation. Of these measurements, 123 were from fluvial sandstone and 185 were from lacustrine sandstone. Streams flowed northward into Lake Uinta in the P.R. Spring area. The considerable scatter in the fluvial paleocurrents suggests that the streams had low gradients and were meandering. Many of the fluvial sandstone bodies are oriented approximately north-south. Lacustrine paleocurrents are generally southeasterly, representing dominantly onshore lake currents. Thus, the shorelines trended northeast through much of the area, although in local embayments shorelines were oriented northwest. The paleocurrent patterns of fluvial and lacustrine sandstone are both unimodal with equal distribution of directions. The 2 environments can be differentiated, however, on the basis of paleocurrent orientations. Fluvial currents flowed northward; lacustrine currents were southerly. Both fluvial and lacustrine sandstones are mostly arkose. Potassium feldspar is more abundant than plagioclase. Quartz-feldspar ratios are greater for lacustrine sandstone than for fluvial sandstone. Lacustrine sandstone contains more quartz and authigenic carbonate and less feldspar, coarse mica, and matrix than fluvial sandstone. Some lacustrine sandstone is also characterized by intraclasts, oolite, fossil fragments, and analcime in contrast to fluvial sandstone. Most of the oil-impregnation is in lacustrine sandstone. Detailed sedimentological study has led to the discovery of new intervals. Such studies will also be useful when these and similar reservoirs are developed. End_of_Article - Last_Page 357------------