Functional morphology and morphometric studies on various mammalian groups have shown marked differences in crania and mandible shape based on dietary preferences and feeding habits. In this study I used three-dimensional geometric morphometric methods to measure the shape of crania and mandibles of herbivorous and omnivorous mammals from three formations in northwestern Nebraska to explore the structure and disparity of ecosystems through time: The White River Group (Chadronian/Orellan/Whitneyan), the Arikaree Group (Arikareean), and the Ogallala Group (Hemingfordian/Barstovian/Clarendonian). Throughout the time period compromising these formations the climatic conditions were becoming more arid, grasslands were expanding and the large mammalian faunal compositions were shifting from browser dominated to grazer dominated. Relative warps analysis show a visible separation of faunas between the three formations that cannot be attributed to phylogeny in plots based on either the crania or the mandibles. Phylogenetic effects were taken into account using generalized least squares. These results indicate that it may be possible to differentiate fossil taxa from different formations and environments based on the shape of cranial and mandibular elements as well as to infer the environment or diet of a fossil if other unequivocal data are not available.

The purpose of this thesis is t o describe the occurrences, interrelationships, and possible origin of the metallic mineral deposits of the Bear River Range. In this study, 21 mineral deposits containing minerals of lead, iron, copper, manganese, and zinc with quartz and carbonate gangue minerals, are described and classified as low temperature epigenetic hydrothermal deposits. The deposits predominantly occur in Cambrian limestone and dolomite formations located below formations with a high shale content. The deposition occurred as fracture filling and replacement along fractures associated with Teritary Basin and Range normal faults and joints which generally trend northerly in the range. No zoning of the deposits was observed. No obvious source for the mineralizing solutions was observed; however, the presence of iron and magnesium minerals in all of the deposits may suggest the possibility of a metamorphic origin. The deposits are dated as post-Eocene.

Seven Cambrian formations and two Ordovician formations, with a total thickness of 9,000 feet, crop out west of the Paris thrust fault and comprise the upper plate. Slices of three Ordovician formations, one Silurian formation, two Mississippian formations, and one formation each of Pennsylvanian and Permian age comprise the low plate. Mesozoic units are not present in the mapped area. Two Tertiary formations and unconsolidated Quaternary deposits are also present. The major structural feature is the Paris thrust fault which extends north-south throughout the area. It was active during the Laramide orogeny. This fault involved eastward movement and placed Cambrian over Ordovician and later Paleozoic strata. The oldest formation exposed in the upper plate is the Brigham Formation which generally rests on the Garden City Formation. All units of the lower plate have been severely distorted and displaced by folding, thrusting, and reverse faulting. Both horizontal compression and gravity sliding have been invoked to explain this deformation. Gravity sliding is favored by many geologists; however, an uplifted source area has not been identified. Later, gravity faulting produced the major topographic features of the area today, notably the Bear River Range and Bear Lake Valley. (76 pages)

The geological column in northern Utah has had very little detailed study. Those who have made reports on this section have done so only in a very general way, making no detailed sections of any part of the column, excepting that of the Cambrian made by Walcott. Other work has been done by Mansfield in southeastern Idaho and a general section of the Devonian made in Green Canyon, Bear River Range, Utah by kindle.

Longitudinal profile, channel cross-section geometry, and depositional patterns of the Green River in its course through the eastern Uinta Mountains are each strongly influenced by river -level geology and tributary sediment delivery processes. We surveyed channel cross sections at 1-km intervals, mapped surficial geology, and measured size and characteristics of bed material in order to evaluate the geomorphic organization of the 70- km study reach. Canyon reaches that are of high gradient and narrow channel geometry are associated with the most resistant lithologies exposed at river level and the most frequent occurrences of tributary debris fans. Meandering reaches that are characterized by low gradient and wide channel geometry are associated. with river-level lithology that is of moderate to low resistance and very low debris fan frequency. The channel is in contact with bedrock or talus along only 42 percent of the bank length in canyon reaches and there is an alluvial fill of at least 12 m that separates the channel bed from bedrock at three borehole sites. The influence of lithology primarily operates through the presence of resistant boulders in debris fans that are delivered by debris flows from steep tributaries. The depositional settings created by debris fans consist of (1) channel-margin deposits in the backwater above the debris fan, (2) eddy bars in the zone of recirculating flow below the constriction, and (3) expansion gravel bars in the expansion below the zone of recirculating flow. These fan-eddy complexes are the storage location of about 70 percent. by area, of all fine- and coarse-grained alluvium contained within the canyons above the low-water stage. Immediately adjacent meandering reaches contain an order of magnitude more alluvium by area but have no debris fan-created depositional settings. This study also describes the flood-plain and terrace stratigraphy of the Green River in the eastern Uinta Mountains and changes due to the operations of Flaming Gorge Dam, upstream from the study area. These landforms are vertically aggrading deposits that are longitudinally correlative throughout the 65-km study reach. The suite of surfaces identified includes a terrace that is inundated by rare pre- or post-dam floods, an intermediate bench that is inundated by rare post-dam floods, and a post-dam flood plain that is inundated by the post-dam mean annual flood. Analysis of historical photographs in the study reach shows that both the intermediate bench and post-dam flood plain are landforms that were not present in any of the 6 years for which photographs were examined between 1871 and 1954. Photographic replications also show that gravel bars consisting of bare gravel in 1922 and earlier photographs are now covered by fine-grained alluvium and vegetation . Decreased gravel-bar mobility is indicated by estimates of critical and average boundary shear stress. Comprehensive surficial geologic mapping of the study area indicates that the bankfull channel has decreased in width by an average of about 20 percent.

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