Published detrital zircon geochronological data was compiled to form the Global Detrital Zircon Database (GDZDb). This database provides a reference block for provenance analysis by future detrital zircon geochronological studies. This project entailed three subprojects: 1. crustal growth/crustal recycling patterns, 2. a provenance study of the Triassic Dry Fork Formation of the Danville-Dan River Rift basin of Virginia and North Carolina, and 3. sample size issues in detrital zircon studies. The global detrital zircon age frequency distribution exhibits six prominent, statistically significant peaks: 3.2-3.0, 2.7-2.5, 2.0-1.7, 1.2-1.0, 0.7-0.5, and 0.3-0.1 Ga. These peaks are also observed when the data is sorted for continent of origin, the tectonic setting of the host sediment and for modern river sediments. Hf isotope model ages were also incorporated into the database where grains were dated with both U-Pb and Hf isotopes. The Hf isotope model ages suggest that the majority of detrital zircons U-Pb ages reflect crustal recycling events that generated granitic magmatism, as most grains exhibited Hf isotope ages that are much older than the corresponding U-Pb age. The Triassic Dry Fork Formation was sampled from a site in southern Virginia in the Danville-Dan River Basin. The detrital zircon age frequency distribution for this formation was strongly unimodal with a peak at 400-450 Ma and a paucity of Grenville-age zircons. Comparison of the Dry Fork sample to published east coast data and to the North American record (from the GDZDb) illustrate the unusual nature of the Dry Fork Formation sample. It is probable that older Grenville zircons were blocked from the rift valley by the rift shoulder. Using the GDZDb a study of sample size was conducted in order to estimate the best sample size to use when trying to constrain the maximum age of sedimentation of the host sediment. Rift basins and active margins exhibited smaller offsets from the youngest zircon grain age to host sediment maximum age than observed in samples from passive margins. This study recommends that at least 50 grains need to be age dated on average in order to best constrain the age of the host sediment. / Ph. D.

The geology along the southern flank of the Uinta Mountains, located north of Vernal, Utah, has been mapped at the 7.5' scale within two quadrangles: the Dry Fork and Steinaker Reservoir Quadrangles. Ambiguities dealing with stratigraphy, structural geology, and geohazards are currently being addressed as a result of this and other mapping projects in the vicinity. The geologic units in the area range in age from Mississippian to Late Cretaceous and include Uinta-sourced Tertiary units. Brief unit descriptions are provided for each of the units exposed in the map area. The main structural influence on the rocks within the area is that of the Uinta Uplift and its southern bounding fault, the Uinta Basin Boundary thrust. Locally, the Deep Creek fault zone overprints and dissects the southernmost flank of the broad Uinta Anticline. Other smaller structurally complex areas and folds exist east of the Deep Creek fault zone. The Deep Creek fault zone is made up of a series of NW-SE trending faults, likely related to the South Flank fault zone. Many authors have inferred dip-slip movement along the South Flank fault zone, but have not supported these claims using kinematic data. Detailed mapping and kinematic data collected within the study area has produced a better understanding of the deformation history along the fault zones in question. The faults within the Deep Creek fault zone have steep, linear traces upon which both vertical dip-slip and very nearly strike-slip (left-lateral oblique-slip, mainly) movement has occurred. The faults of the Deep Creek fault zone are likely Paleocene in age. The data suggest a bimodal history of deformation which the principal stress field does not seem to be influenced by typical east-northeast-west-southwest Laramide orogenic far-field stresses. The creation and early history of these faults may have been due to localized stress fields related to activity of the underlying Uinta Basin Boundary thrust, or a later period of uplift, a possible accommodation zone between the western and eastern domes of the Uinta Mountain Range, a transfer zone between the Uinta Basin Boundary thrust and the Asphalt Ridge fault, or a combination of these.