The purpose of this study is to compare the sandstone composition and trace element geochemistry between samples representing the Summit Creek sandstone, Naches, Chumstick, and Carbonado Formations in order to determine if these sediments were all derived from the same provenance, and to determine the composition of the source rocks in hopes to identify the present day location of the source areas.

This study outlines the ash (tuff) bed stratigraphy (tephrostratigraphy) in the middle Eocene Chumstick Formation of central Washington. The tuff beds provide local marker beds enabling interpretation of the stratigraphy and structure of the formation. The chemical signature of these units provides the basis on which the units can be traced over broad areas in the basin of deposition. Correlations of tuff beds were obtained over distances of 41 km.

The Quercy area of France is an important site for mammal palaeontology, yet 19th century collections of this area, such as the one in the Department of Palaeobiology, Naturhistoriska riksmuseet, remain understudied due to not being well updated taxonomically and correlated stratigraphically. An updated taxonomy was created for the postcranial material of the collections, as well as the dental material originally identified to the amphicyonid genera Amphicyon, Haplocyon and Pseudocyon through study of morphological characteristics and measurements. Most of the postcranial material was assigned to a family, which would allow comparison of different morphotypes to gain insight into questions on locomotion, posture and overall ecology. The dental material was reidentified to include the amphicyonids (bear dogs) Amphicyonidae gen. indet. sp. indet, Pseudocyonopsis, Cynelos and Haplocyon, as well as the mustelid Ischyrictis zibethoides. Stratigraphic ranges for the identified species were obtained from existing studies. This updated taxonomy would allow for future study of this material to improve the overall understanding of Quercy, as well as the taxa present in these localities.

No description available.

A well-preserved Paleocene flora of 39 species from the Fort Union Formation near Baggs, Carbon County, Wyoming has been studied. This is the first study of the plant megafossils in this area. The most abundant species collected are: Carya antiquorum Platanus nobilis, Cercidiphyllum arcticum and Platanus raynoldsi. Together they represent 74% of the flora. The flora has been dated as Upper Middle Torrejonian. This report is also the first paleoecological study of any North American Paleocene flora. Two methods were used to determine the paleoclimatic conditions of the flora. The first was an analysis of leaf margin characteristics, comparing them to characteristics of modem floras. The second method was an analysis of leaf size comparing the average leaf length and leaf size profile to that of modern floras. Both of these studies suggest that this flora lived in a warm-temperate to subtropical, seasonably dry to moist climate. A correlation of the identified species to their nearest living relatives and their favored climates supports this conclusion.

Climate change across the terrestrial Eocene-Oligocene boundary of the Great Plains is recorded by shifts in sediments, facies, paleosols, and isotopic records, and is interpreted as a shift to overall cooler and drier conditions. As an independent test of paleoenvironmental shifts caused by climatic change, I compared microwear on M2 molars of Leptomeryx from the White River Group (WR) at Toadstool Park, Nebraska (n = 9) and Flagstaff Rim, Wyoming (n = 11). Comparisons of microwear were made through time at each section. Various measurements of microwear were quantified on original, uncoated specimens using environmental scanning electron microscopy and Microware 4.0 software, and evaluated with ANOVA and Kruskal-Wallis statistical tests. Values of the scratch:pit ratio, scratch number, feature major:minor axis ratio, feature vector length, major axis standard deviation, major:minor axis standard deviation, and feature orientation standard deviation for Leptomeryx M2 molars are significantly different (p<0.05) between Wyoming and Nebraska. Microwear patterns suggest paleoecological differences between the two locations, possibly related to differences in Leptomeryx diet or in amount or character of sediment adhering to ingested vegetation. Little fossil evidence of vegetation type is preserved at either locality, other than clay-filled root traces or occasional rhizoliths or silicified fragments. However, sediments of the WR are a mixture of volcaniclastic enriched mudstone, siltstone, and sandstone, with generally coarser overall particle sizes in Wyoming that reflect proximity to siliciclastic sources. The degree of overall volcaniclastic enrichment and number of airfall tuffs is also higher at Flagstaff Rim. Paleosols suggest a shift from closed canopy forest to progressively open conditions at each locality and, although microwear differences could result from differences in vegetation or particle sizes of adhered sediments on plants, no or very low correlations between microwear features and stratigraphic level were detected at either locality, indicating that any changes in paleoecology over time did not significantly alter the diets of Leptomeryx, although diet may have been geographically different. / Geology

Dynamic Systems modeling suggests that complex coastal dinoflagellate biosystems can be modeled using environmental parameters such as temperature, salinity, and bulk nutrient levels. The former Salisbury Embayment of northern Virginia and Maryland is modeled here, using STELLA I and FORTRAN models based on physical oceanography and temperature, salinity, and nutrient conditions of the modern Yellow Sea. In these models, dinoflagellate assemblages are predicted based on environmental conditions associated with depth. Cluster analyses of fossil dinoflagellate frequency data from Tertiary Pamunky Group (Aquia and Nanjemoy Formations) of the Salisbury Embayment produce 17 discrete groupings. Samples within the Salisbury fossil cluster groups are statistically similar (via ANOVA analysis), but not the same. Therefore they represent paleocommunity types rather than paleocommunities. Although individual sinofiagellate species recur in similar environmental settings, the paleocommunity types do not appear to repeat. In the past, such associations have been used as depth indicators. It is suggested here that they relate to estuarine, nearshore, and offshore coastal regions because of the temperature, salinity, and nutrient conditions of each. In the modern Yellow Sea, nearshore and offshore regions are separated by discrete lateral fronts in some areas, and by gradational regions of mixing in others. Both types of water mass boundaries are modeled in this study. Results suggest that evidences that discrete water mass boundaries might have occurred between some fossil dinoflagellate associations. Circulation patterns of the Salisbury Embayment may have been roughly similar to those of the modern Yellow Sea. / Master of Science

Atlantic Meridional Overturning Circulation (AMOC) is a vital process that transfers heat and nutrients throughout the world's oceans, helping to regulate global climate and support marine ecosystems. The timing and nature of the shift to modern AMOC, and especially to deep-water formation in the North Atlantic, has been a topic of ongoing study, with the Eocene-Oligocene Transition (EOT, ~34 Ma) as a potential focal point of this shift. However, the role played by abrupt EOT cooling and Antarctic glaciation in North Atlantic circulation remains unclear. Improved constraints on Paleogene circulation will provide insight into the sensitivity of AMOC to perturbations in global climate, which is particularly relevant in light of contemporary climate change. To examine deep North Atlantic circulation response to the EOT we obtained grain-size data from the terrigenous fraction of the mud-dominated sediments of the Southeast Newfoundland Ridge contourite drift complex at IODP Site U1411, which is interpreted to have formed under the influence of the Deep Western Boundary Current. We analyzed 195 samples that span 150 m of stratigraphy from 36-26 Ma. The main objective was to use the 'sortable silt' fraction (10-63 µm) to generate a record of relative change in bottom-current intensity. These data are complemented with a record of the abundance and size of lithogenic sand (>63 µm). Here we present the first physical proxy record of abyssal current intensity in the North Atlantic, from late Eocene to mid Oligocene. Invigoration of North Atlantic deep circulation occurred gradually (over Myr timescales), with no significant changes linked temporally to the EOT. We infer that deep circulation in the North Atlantic was not sensitive to the abrupt global cooling and Antarctic glaciation associated with the EOT. Rather, our data suggest that changes in North Atlantic circulation were likely governed by longer-term processes related to the opening of key tectonic gateways, such as the Greenland-Scotland Ridge in the North Atlantic, and the Drake and Tasman Passages in the Southern Ocean. Additionally, we identify a significant mid-Oligocene invigoration of North Atlantic abyssal circulation, which climaxes around 27.9 Ma, and is coeval with a decrease in atmospheric CO2. / Master of Science

The Sand Wash Fault Zone (SWFZ) in the southern Uinta Basin is a significant extensional fault zone exhibiting complex deformation patterns. Our study integrates detailed structural analyses with a broader tectonic model to elucidate the tectonic evolution of the region. The SWFZ, extending over 34 km with a NW-SE strike, is underlain by an extensional decollement. Substantial deformation is observed in the upper layers, notably within the S2 sandstone of the Eocene Green River Formation. The deformation diminishes with depth, terminating at the oil-rich Mahogany oil shale zone, below which minimal deformation is observed. Our tectonic model, developed primarily through outcrop analysis utilizing Eocene-age outcrops, borehole breakouts, and dike and joint systems, highlights three key stages in the development of extensional fault zones related to the Uncompahgre Uplift within the Uinta Basin. Initially, eastward-directed contraction beginning during the late Cretaceous reactivates Precambrian oblique strike-slip faults, coinciding with the latest Uncompahgre Uplift event. Regional Laramide stress develops NW-SE joint patterns throughout the Uinta basin. Subsequently, reactivated Precambrian faulting leads to the formation of tight drape folds, with extensional stresses enhancing the regional Laramide stress regime deformation patterns along the axial plane of the drape folds. Finally, late Eocene orthogonal flexure results in extensional faulting along Precambrian faults. Maximum stress (σ1) of the SWFZ during its development was oriented vertically, while minimum stress (σ3) was perpendicular to the fault zone at approximately NE-SW, matching the trend of the Laramide stress regime. In the Devils River Uplift region, the Laramide stress regime resulted in the formation of 0.5m scale drape folds and anticlines, whose axes ultimately experienced orthogonal flexure, thereby resulting in the development of neutral-surface extensional features (Ferrell et al., 2022). Results from the regional tectonic model provide additional insights into stress orientations and timing, elucidating the role of reactivated Precambrian faults and orthogonal flexure in shaping the structural evolution of the southern Uinta Basin. Integration of these findings increases our understanding of fault zone development and serves as an analog for similar systems in the western USA.

Sections in and around Badlands National Park, Custer County, South Dakota contain a wealth of faunal and floral data within the White River Group. The Chadronian and Orellan North American Land Mammal Ages define the Eocene-Oligocene boundary here. Faunal and floral changes associated with the Chadronian-Orellan interval have long been attributed to the global Greenhouse-Icehouse climatic transition. Stable isotopes were obtained from paleosol carbonates across the Chadronian-Orellan boundary at three locations in Badlands National Park. Results show wide fluctuations of oxygen isotopes in the uppermost Chadronian and lower Orellan, while carbon isotopes remain relatively stable. The records provide an opportunity to compare the continental response to global change with a near-shore marine system response (Gulf Coastal Plain, USA); and to the world at large. Results indicate a decoupling of the terrestrial response to the Oi-1 glacial event from the marine response. Local conditions appear to play an important role in controlling the record of stable isotopes in paleosol carbonates in the region. / Geologic history of the Eocene-Oligocene -- Climate records -- Causes of climate change -- Climate change across the Eocene-Oligocene -- Current findings -- Discussion. / Department of Geology