Fluvial systems and their associated deposits host globally important mineral deposits, water reserves and hydrocarbons. Crucial to the extraction of these resources is an understanding of heterogeneity distribution within deposits of fluvial systems. To constrain and predict heterogeneity distribution within fluvial deposits, outcrop data together with lidar and drone derived virtual outcrop models have been collected from the Salt Wash Distributive Fluvial System (DFS) in Utah and Colorado. The study records an analysis of sedimentary architecture, facies distribution and intra-channel heterogeneity of five study sites within the proximal, medial and distal reaches of the Salt Wash DFS. Specifically the fluvial style, lateral variability of fluvial architecture, intrachannel and overbank ratio, grainsize, channel body and storey width:thickness ratios and intrachannel heterolthics at outcrops considered representative of the proximal, medial and distal portions of a DFS have been documented. Data from the study sites have been used to generate 3D reservoir models. The models have been subject to flow simulation to better understand the significance of hetergenity variability within fluvial reservoirs at an 'inter-well' scale (approximatley 0.1 km2). An indepth workflow and methodology for measuring and describing DFS channel bodies and for the construction of a reservior flow simulation model from outcrop derived data are presented here. Data collection has involved mapping and measuring; palaeocurrents, barscale accretion surfaces, storey dimensions, channel body dimensions, facies and intrachannel heterolithics. Results show clear trends within channel channel bodies and associated deposits such as, intra channel heterogenity channel body percentage, channel body grain size, storey/channel body width thickness; which can be predicted within a distributive fluvial system context, ultimately leading to better subsurface interpretation with smaller datasets. This field based study of the Salt Wash DFS, coupled with virtual outcrop models has provided a quantitive analys's of channel body architectures and facies distributions. Additionally, field work conducted on point bar deposits now illustrates the limitations of 2D outcrops when attempting to describe meandering or braided fluvial deposits and why this may have resulted in gross underestimation of meanderbelt deposits in the fluvial rock record.

Thesis (M.S.)--Brigham Young University. Dept. of Geological Sciences, 2006. / Includes bibliographical references.

Universiẗat, Diss., 2003--Bonn.

The Middle-Upper Jurassic sedimentary rocks (i.e., the Entrada Sandstone, Wanakah Formation, and Morrison Formation) in western Colorado were mostly deposited in the Paradox Basin and form part of the modern-day Colorado Plateau in the Cordilleran foreland region. These rocks were deposited in the Mesozoic during periods of active tectonic processes in western and eastern Laurentia due to the Cordilleran magmatism and continued rifting of Pangaea, respectively. The Middle-Late Jurassic sedimentary record in the Paradox Basin shows rapid transition in depositional environments, pulses in sedimentation, post-depositional alteration, and changes in provenance. This dissertation project utilizes three main scientific tools to address pertinent geologic questions regarding the stratigraphic evolution of these units in the Paradox Basin. U-Pb detrital zircon geochronology of sandstones from these units show local and distal provenance sources. The anisotropy of magnetic susceptibility (AMS) of sediments and rock magnetism attribute the post-depositional alteration to percolation of ferruginous fluids driven by an adjacent regional uplift. Multi-geochemical proxies in paleosols suggest variable redox conditions, and a sub-humid to humid paleoclimate with seasonal precipitation during sedimentary hiatus in the Paradox Basin.

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The Lower Cretaceous Cedar Mountain Formation preserves several vertebrate faunas and has the potential of providing critical timing information pertaining to Early Cretaceous dinosaurs and the Sierran magmatic arc. Historically, the Morrison/Cedar Mountain contact and the duration of the unconformity between them have been difficult or impossible to determine because 1) the formations were deposited in similar environments, 2) the basal Cedar Mountain Formation is composed of reworked Morrison Formation, and 3) there are no radiometric ages for the lower Cedar Mountain Formation. A stratigraphic study through central Utah reveals a diagnostic suite of pedogenic and sedimentologic characters across the previously enigmatic boundary. The uppermost Morrison Formation is characterized by redoximorphic paleosol features, including iron concentrations, manganese-coated grains, and intense red-purple-green mottling. Upsection increases in chert-pebble lags and channelized conglomerates within the paleosol section indicate a period of reduced accommodation space in the Tithonian. The paleosols are usually capped by a groundwater or pedogenic carbonate. This unit is consistently present from Green River, Utah to the Utah-Colorado border. The lower Cedar Mountain Formation above this package is a poorly sorted mixture of fine-grained material and sand-gravel sized chert grains. Within a sequence stratigraphic framework, these characters record a terrestrial sequence boundary in the uppermost Morrison Formation and degradational-aggradational systems tracts in the Cedar Mountain Formation. To resolve the lack of age control for the basal Cedar Mountain Formation, a geochronologic zircon study was conducted near the Dalton Wells dinosaur quarry, Moab, Utah. The Dalton Wells quarry, along with numerous other fossil assemblages occurs in the basal Yellowcat Member. Zircons from the Dalton Wells quarry and a correlative eggshell site place the age of this horizon near the Barremian/Aptian boundary at ~124 Ma. Thus, the Yellowcat fauna is time equivalent with the feathered dinosaurs of the Yixian Formation, of Liaoning, China. This age constrains the Morrison/Cedar Mountain unconformity to a period of magmatic quiescence in western North America from 148 Ma-124 Ma. The basal Cedar Mountain age coincides with renewed magmatic activity at ~125 Ma. The Cedar Mountain Formation covers a period of 27 Myr and likely contains numerous small unconformities.

Mineralogical and petrographic analyses of the upper Jurassic - lower Cretaceous units in the vicinity of the Dinosaur National Monument quarry near Jensen, Utah, have elucidated their characteristics and the locations of formational boundaries. The lower part of the Morrison Formation is distinguished by a decreased amount of illite and an increased amount of kaolinite. In contrast, the underlying Curtis Formation contains an approximately equal mixture of illite and kaolinite. The lower Salt Wash Member and the upper Brushy Basin Member of the Morrison are both lithologically and mineralogically identifiable in this area. Above the boundary between the two, kaolinite decreases and illite increases. The strata above the Morrison, here recognized as an extension of the Cedar Mountain Formation, reveal another change in clay content. They contain kaolinite as the dominant clay mineral, whereas illite is almost completely absent. The upper Curtis Formation is a near-shore marine deposit, whereas the members of the Morrison Formation are fluvial and lacustrine. A possible climatic or depositional change is equated with the changes in the clay content within the members of the Morrison Formation. After deposition of the Morrison, the lower Cretaceous sediments that now comprise the Cedar Mountain Formation accumulated. These formed in a transitional zone (fluvial to littoral) and were eventually covered by the Dakota Formation (littoral) and the Mowry Formation (marine).