Browsing by Author "Egenhoff, Sven, committee member"

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Open Access
A new method to test shear wave splitting: improving statistical assessment of splitting parameters
(Colorado State University. Libraries, 2016) Corbalán Castejón, Ana, author; Schutt, Derek, advisor; Breidt, Jay, committee member; Aster, Richard, committee member; Egenhoff, Sven, committee member
Shear wave splitting has proved to be a very useful technique to probe for seismic anisotropy in the earth’s interior, and measurements of seismic anisotropy are perhaps the best way to constrain the strain history of the lithosphere and asthenosphere. However, existent methods of shear wave splitting analysis do not estimate uncertainty correctly, and do not allow for careful statistical modeling of anisotropy and uncertainty in complex scenarios. Consequently, the interpretation of shear wave splitting measurements has an undesirable subjective component. This study illustrates a new method to characterize shear wave splitting and the associated uncertainty based on the cross-convolution method [Menke and Levin, 2003]. This new method has been tested on synthetic data and benchmarked with data from the Pasadena, California seismic station (PAS). Synthetic tests show that the method can successfully obtain the splitting parameters from observed split shear waves. PAS results are very reasonable and consistent with previous studies [Liu et al., 1995; Özalaybey and Savage, 1995; Polet and Kanamori, 2002]. As presented, the Menke and Levin [2003] method does not explicitly model the errors. Our method works on noisy data without any particular need for processing, it fully accounts for correlation structures on the noise, and it models the errors with a proper bootstrapping approach. Hence, the method presented here casts the analysis of shear wave splitting into a more formal statistical context, allowing for formal hypothesis testing and more nuanced interpretation of seismic anisotropy results.
Open Access
Coupled continuum pipe-flow modeling of Karst groundwater flow in the Madison limestone aquifer, South Dakota
(Colorado State University. Libraries, 2013) Saller, Stephen Paul, author; Ronayne, Michael, advisor; Sale, Thomas, committee member; Egenhoff, Sven, committee member
Karst carbonate aquifers are traditionally difficult to model due to extreme permeability heterogeneities and non-Darcian flow. New modeling techniques and test applications are needed to improve simulation capabilities for these complex groundwater systems. This study evaluates the coupled continuum pipe-flow framework for modeling groundwater flow in the Madison aquifer near Rapid City, South Dakota. The Madison carbonate formation is an important source of groundwater underlying Rapid City. An existing equivalent porous medium (EPM) groundwater model of the Madison aquifer was modified to include pipe networks representing conduits. In the EPM model, karstified portions of the aquifer are modeled using high hydraulic conductivity zones. This study hypothesized that the inclusion of conduits would allow for a simpler hydraulic conductivity distribution and would improve modeled fits to available data from a 10-year monitoring period. Conduit networks were iteratively fit into the model based upon available environmental and dye tracer test data that approximated major karst pathways. Transient simulation results were evaluated using observation well hydraulic heads and estimated springflow data. In a comparison to the EPM model, the new modeling results show an improved fit to the majority of observation well targets, and negligible impact to springflow data. The flow dynamics of the aquifer model were significantly altered, with the conduit networks acting as gaining or losing subsurface features, behaving as regional sinks during dry periods and flowpath heterogeneities during wet periods. The results of this study demonstrate that the coupled continuum pipe-flow modeling method is viable for use within large regional aquifer models.
Open Access
Fluid inclusion and metal ratio analysis of Cordilleran Pb-Zn-Cu-(Ag-Au) veins of the Montezuma district: Summit County Colorado, USA
(Colorado State University. Libraries, 2015) Pyanoe, Dominic, author; Ridley, John, advisor; Egenhoff, Sven, committee member; Wilson, Bob, committee member
Evidence from fluid inclusion microthermometry in Pb-Zn-Cu-(Ag-Au) veins and district scale metal ratio zonation analysis indicate that the Cordilleran veins of the Montezuma mining district Summit County, Colorado, USA are indicative of subepithermal setting about a central hydrothermal source. Cordilleran-type polymetallic mineralization is a class of ore deposits that are spatially and temporally related to felsic igneous centers and can also be genetically related to porphyry mineralization (Fontboté and Bendezú, 2009). At Montezuma, the Teritary-aged Montezuma Stock is cross cut by several Cordilleran-type veins and is spatially related to over 80 additional veins hosted in Precambrian country rock. Five stages of mineralization in veins are identified: Stage 1. early quartz-pyrite, Stage 2. barite-incipient base metals Stage 3. base metals, Stage 4. carbonates and Stage 5. late quartz-lead-silver. There is a systematic decline in precipitation temperatures from 341 to 156°C along the progression of the paragenetic sequence, which suggests the waning of a source pluton. District scale metal ratio zonation maps from historical production data support the interpretation of a central magmatic source and that thermal decline is the primary control on ore deposition. Two district scale zones are identified: a copper rich zone (CRZ) in the center of the district, which is surrounded by a copper poor zone (CPZ). With distance from the inferred center of the district, there is a general decline in copper abundance relative to lead and silver. Thermal gradients accompanied by a decrease in metal solubilities are the mechanism for this zonation pattern, but developed late in the paragenesis. Other chemical and physical controls of phase separation, ligand removal, dilution and pH increase are likely present during vein mineralization as well. Approximate salinities ranged from 11.69 to 3.70 wt.% equivalent NaCl and showed less systematic patterns, and may reflect these additional processes. Temperature decline and variable additional depositional processes are consistent with analogous Cordilleran-type vein fields, which have proven links to a magmatic source and possible underlying stockwork porphyry base metal mineralization. Therefore, data from this study indicates that there is most likely porphyry Mo mineralization under the copper rich zone, but this may be sub economic in nature.
Open Access
Fluid inclusion study of the Mesoproterozoic Nonesuch Formation - biogenic sources and thermal history of oil
(Colorado State University. Libraries, 2011) Colbert, Sarah Janette, author; Ridley, John, advisor; Egenhoff, Sven, committee member; Kennan, Alan, committee member
The Nonesuch Formation is part of the Mid-Continent Rift System and is unusual because it contains a relatively high amount of oil that is thought to have formed in situ during the Mesoproterozoic, approximately 1.1 Ga. In this study, primary, pseudosecondary and secondary oil inclusions in samples obtained from Nonesuch Fm outcrop and cores were analyzed using petrography and microthermometry, and one core sample was analyzed by GC-MS. Aqueous inclusions were also studied via petrography and microthermometry. The inclusions studied were hosted in sandstone grains and matrix from parts of the Nonesuch Fm and the upper part of the Copper Harbor Fm, diagenetic calcite nodules from the Marker Bed of the Nonesuch Fm and calcite veins in the Nonesuch and Upper Copper Harbor Fms that formed no later than 30 Ma after deposition. Based on these settings, it can be assumed that all inclusions studied were entrapped during the Mesoproterzoic around the time of deposition of the Nonesuch Fm. The biomarkers detected by GC-MS have a Proterozoic character and the presence of mid-chain substituted monomethyl alkanes as well as 1,2,5-TMN indicates a cyanobacterial hydrocarbon source. Algal biomarkers have also been found in the oil in previous studies. The ratios calculated from the GC-MS data suggest an early- to peak-oil window maturity for the hydrocarbons, which is consistent with data from previous studies. The homogenization temperatures obtained by microthermometry are typically used as an estimate of inclusion entrapment temperature; however, in this study, the wide range of homogenization temperatures along with an inconsistency between these and the GC-MS maturity indicators implied that the thermal history of the oil was more complex. The inclusions were likely trapped during diagenesis at temperatures between 100-130°C, which agrees with the evidence from the maturity ratios and previous work on the Nonesuch Fm, and then reheated by hydrothermal activity after entrapment. The microthermometrical evidence implies that the second period of heating raised temperatures to levels exceeding 250°C, and other studies of the Mid-Continent Rift area suggest that this secondary heating occurred either soon after diagenesis or significantly later, around 200-300 Ma.
Open Access
Geophysical constraints on the flexural subsidence of the Denver Basin
(Colorado State University. Libraries, 2012) Abdullin, Ayrat, author; Harry, Dennis L., advisor; Egenhoff, Sven, committee member; Lefsky, Michael, committee member
The Denver Basin is an asymmetric Laramide (Late Cretaceous through Eocene) foreland basin covering portions of eastern Colorado, northwestern Kansas, southwestern Nebraska, and southeastern Wyoming, USA. It is bordered on the west by the Rocky Mountain Front Range Uplift, a basement cored Laramide anticline bounded by thrust faults, and on the east by the Great Plains and stable North American craton. A ~400 mGal negative Bouguer gravity anomaly exists over the Denver Basin and Front Range Uplift, with its minimum located over the highest topography in the central part of the uplift, approximately 100 km west of the Denver Basin. This study examines three hypotheses concerning the isostatic state of the basin and adjacent Front Range Uplift. These hypotheses are that the modern shape of the basin is due to: 1) flexure of the lithosphere under the surface load of the current topography, or 2) flexure under a subsurface load beneath the Rocky Mountains, or 3) a combination of both surface and subsurface loads. To test these hypotheses, spectral analysis and forward gravity modeling was conducted along three profiles located in the northern, central, and southern parts of the basin. Bouguer gravity power spectra along the profiles reveal 5 major density interfaces interpreted to represent the base of the lithosphere (at depths of 132 to 153 km), base of the crust (45-55 km), a mid-crustal boundary (about 20 km), the top of Precambrian basement (1-2 km), and a boundary between the Pierre Shale and Niobrara Formations within the pre-Laramide sedimentary section (-1-0 km). Flexural modeling shows that the shape of the basin can be fit with an elastic plate model having a line load of magnitude 2-5 x 1012 N/m and an elastic thickness of the lithosphere of 58-80 km. The location of the load is 90-115 km west of the Bouguer gravity minimum on each profile. The gravity anomaly associated with flexural subsidence of the basin, assuming the layered density structure derived from the spectral analysis, is calculated to reach a minimum of -60 mGal, only 15 % of the observed Bouguer gravity anomaly. The magnitude of the load is less than the present topography weight of 3.63-4.65 x 1013 N/m, indicating that the weight of the Rocky Mountain Front Range is only partially compensated by flexural isostasy. Since seismic data indicate a lack of a pronounced crustal root, a buoyant subsurface load is required (hypothesis 3). Forward gravity models, supplemented with available well and seismic refraction data, are developed to test four end-member hypotheses as to the location of the buoyant subsurface load. We consider in turn that the load lies entirely within the: (1) asthenosphere, (2) shallow lithosphere mantle, (3) lower crust, or (4) upper crust. The models show that the subsurface load is unlikely to lie entirely within any of the depth intervals investigated. The study indicates that the buoyant subsurface load is partitioned in some combination between low-density crust and/or low-density lithospheric and/or asthenospheric mantle. In all of the gravity models, the crust thickens abruptly at the boundary between the Rocky Mountains and Great Plains, from about 48 km beneath the Denver Basin to about 53 km beneath the Front Range Uplift.
Open Access
Instantiating time: object as metaphor
(Colorado State University. Libraries, 2019) Forsythe, Alexandra, author; Bates, Haley, advisor; Egenhoff, Sven, committee member; Emami, Sanam, committee member; Ryan, Ajean, committee member
This body of work reflects personal research into the characteristics of time, specifically memory in relation to site, and our human relationship with the natural world. Time is relative, not absolute. Each individual has a unique perspective, from the speed at which time passes to recollection of the past to speculation into future events. Through the dual lenses of the personal and the geologic, I engage with perceptions of spatiotemporal experience. Exploration of the souvenir as a physical representation of memory and site is contrasted against the expansive theory of deep time. Through repetitive, time intensive methods grounded in traditional ways of making I create objects that both embody and represent time. By interacting directly with the body, my wearable pieces allow for an intimate engagement with these ideas; the non-wearable work provides space for reflection on the nature of time and memory.
Open Access
Mantle velocity variations under the northern Canadian Cordillera through body wave tomography
(Colorado State University. Libraries, 2019) Khare, Aditya U., author; Schutt, Derek, advisor; Buchanan, Kristen, committee member; Egenhoff, Sven, committee member
The Mackenzie Mountains (MM) in the northern Canadian Cordillera (NCC) are an actively uplifting mountain range and an excellent location to investigate the causes of intra-plate orogeny. The orogen is situated almost ~750 km inboard of the active Pacific plate boundary, and little deformation is occurring between the MM and the Pacific Coast, except within the Coast Ranges. To investigate the causes of this orogeny, the Mackenzie Mountains Earthscope Project (MMEP) deployed 40 broadband seismographs and 4 continuous GPS instruments in a linear array from near the Pacific Coast to the Slave craton. Here we present results of teleseismic body wave tomography in the NCC that were obtained by using data from 37 of these MM stations as well as 67 other stations in the region surrounding the MM. Results show a sharp sub-vertical transition between low velocity in the Cordillera (ΔV -2%) and high velocity in the craton (ΔV +2%) about 100 km southwest of the Mackenzie River. The locations of Miocene to Present volcanism in the region also coincide well with the low velocity zones suggesting the presence of melt and/or anomalous temperatures. Two notable high velocity anomalies are seen beneath the Cordillera. The first is present under the Tintina Fault (ΔV +1.5%) and may be indicative of a lower crustal compositional anomaly. The other is at 600 km depth below the Cordillera (ΔVp +2%) which we interpret as delaminated lithosphere. The delamination possibly resulted from mantle upwelling due to the opening of the slab window ~20 Ma.
Open Access
Measuring seismic anisotropy in the mantle wedge of Japan's subduction system using shear wave splitting of SKS and SKKS waves
(Colorado State University. Libraries, 2014) Pierce, Jamie, author; Schutt, Derek, advisor; Breidt, Jay, committee member; Egenhoff, Sven, committee member; Elkins, Joe, committee member; Harry, Dennis, committee member
Mantle flow patterns can provide a better understanding of mantle deformation and composition in subduction systems. These flow patterns can be inferred by measuring seismic anisotropy. Previous anisotropy studies of Japan's subduction system have found complex fast axis polarizations. Here we seek to better constrain fast axis directions through shear wave splitting of SKS and SKKS waves from events with magnitudes greater than 6.5. Data were collected from the Japanese National Research Institute for Earth Science and Disaster Preventions (NIED) F-net array for stations located over all of Japan. Results from shear wave splitting measurements show trench-parallel fast axes trends near the Ryukyu and Japan Trenches and trench-perpendicular fast axes further away from these trenches. Fast axes near the Nankai Trough align with the subducted plate motion. The Kuril Trench fast axes are roughly perpendicular to subducted plate motion. A simple 2D corner flow model can explain the flow of the mantle wedge if B-type olivine deformation, indicative of hydrated asthenosphere under high stress, is the source of the fast axes perpendicular to mantle flow direction near the Ryukyu Trench, Japan Trench, and Kuril Trench.
Open Access
People power from Liberation Square to Aleppo: a comparative analysis of nonviolent resistance in the Arab Spring
(Colorado State University. Libraries, 2017) Olson, Philip Robert, author; Cavdar, Gamze, advisor; McIvor, Dave, advisor; Egenhoff, Sven, committee member
Beginning with Gene Sharpe's seminal work The Politics of Nonviolent Action (19741) strategic nonviolent action has been touted as an alternative to violent insurrection against repressive regimes, and, in its earliest hours, many touted the Arab Spring as a powerful example of nonviolent resistance in the face of longstanding and well-armed bastions of power. However, the epithet "Liberation Square" imprinted on the architectural center of the protests that overthrew Hosni Mubarak has faded, while the architectural centers of Aleppo, Manama, and Misrata no longer exist. However, the Arab Spring should not be forgotten by nonviolent actors. By mapping the methods, both the successes and failures, and the dynamics of resistance as it spread across the region this project forwards three central arguments regarding nonviolent action. First, participants in civil resistance do not maintain uniform agency across cases, and structural conditions play a significant role in determining the success of nonviolent resistance. Second, nonviolence should not be an ultimatum, and integrating violent strategies of resistance can bolster resiliency and strength. Finally, nonviolence is not a panacea, and should be contextualized within the political and economic contexts of resistance.
Open Access
Seafloor spreading in the eastern Gulf of Mexico: new evidence for marine magnetic anomalies
(Colorado State University. Libraries, 2014) Eskamani, Philip K., author; Harry, Dennis, advisor; Egenhoff, Sven, committee member; Robinson, Raymond, committee member
Possible sea-floor spreading anomalies are indentified in marine magnetic surveys conducted in the eastern Gulf of Mexico. A symmetric pattern of lineated anomalies can be correlated with the geomagnetic time scale using previously proposed opening histories for the Gulf of Mexico basin. Lineated magnetic anomalies are characterized by amplitudes of up to 30 nT and wavelengths of 45-55 km, and are correlatable across 12 different ship tracks spanning a combined distance of 6,712 km. The magnetic lineations are orientated in a NW-SE direction with 3 distinct positive lineations on either side of the inferred spreading ridge anomalies. The magnetic anomalies were forward modeled with a 2 km thick magnetic crust composed of vertically bounded blocks of normal and reverse polarity at a model source depth of 10 km. Remnant magnetization intensity and inclination are 1.6 A m-1 and 0.2° respectively, chosen to best fit the magnetic observed amplitudes and, for inclination, in accord with the nearly equatorial position of the Gulf of Mexico during Jurassic seafloor spreading. The current magnetic field is modeled with declination and inclination of and 0.65° and 20° respectively. Using a full seafloor spreading rate of 1.7 cm/yr, the anomalies correlate with magnetic chrons M21 to M10. The inferred spreading direction is consistent with previous suggestions of a North-East to South-West direction of sea-floor spreading off the west coast of Florida beginning 149 Ma (M21) and ending 134 Ma (M10). The opening direction is also consistent with the counter-clockwise rotation of Yucatan proposed in past models.
Open Access
Sedimentary character and processes in mudstone inter-lobe deposits of the Skull Creek Formation, Fort Collins, Colorado
(Colorado State University. Libraries, 2025) Abukhtwa, Ahmed, author; Gallen, Sean, advisor; Schutt, Derek, committee member; Egenhoff, Sven, committee member; Aoki, Eric, committee member
Lobe-fringe deposits and interlobe strata are rarely described in sedimentary systems and often neglected in descriptions of delta successions, which mostly focus on delta top, delta front, and prodelta sediments. This may partly be the case because these deposits consist mostly of mudstones, which are generally neglected in all sedimentary systems except for black shales. Here, we describe nine siliciclastic facies of predominantly mudstones from the Cretaceous Skull Creek Formation of northern Colorado, USA. These nine facies are arranged in a 4.5 m thick predominantly fine-grained unit within the overall 25 m thick Skull Creek Formation. The nine facies are very fine to fine-grained dark massive mudstone lamina (F1), very fine-grained massive mudstone (F2), massive fine- to coarse-grained mudstone (F3), massive mudstone with fecal strings (F4), normally graded coarse to medium-grained mudstone (F5), medium- to coarse- grained lenticular siltstone (F6), siltstone lamina (F7), and massive calcitic coarse silt- to coarse-grained sandstone (F8A and F8B). From all these facies, massive fine- to coarse-grained mudstone (F3), normally graded coarse to medium-grained mudstone (F5) and siltstone lamina (F7) are the most common and comprise about 80-90 vol% of the succession. The succussion consists of 16 coarsening- and fining-upward cycles, with the majority being coarsening- upwards (11), and only (5) fining-upwards. Stratigraphically, these cycles are between 5.5 and 120 mm thick, and are here subdivided into nine distinct stratigraphic zones. These zones alternate between five fine-grained and four silt-rich zones. Each zone consists of a minimum of a portion of a cycle, and/or one or more coarsening- and fining-upwards units. These facies were deposited in three depositional environments: lobe-fringe area, medial inter-lobe area, and distal inter-lobe area. The presence of both high-energy indicators, such as clay clasts, sharp erosional bases, scours, and fragmented fishbones, as well as the occurrence of sediments reflecting suspension deposition, indicates that the lobe-fringe environment was undergoing successive shifts from high to low energy conditions. Moving farther away from the lobe, sediments show overall moderate energy conditions reflected in normal grading and some erosional contact; nevertheless, moderate and low-energy conditions alternated. Furthest away from the lobe are the distal inter-lobe sediments that show tranquil sediment deposition with only minor moderate energy deposition reflected in sharp facies contacts, and some siltstone grains in facies 3. The presence of only one type of fecal string, in these sediments, and the little bioturbated nature of inter-lobe strata suggests that the environment had been likely dysoxic and stressed but was not entirely anoxic. This study indicates that the Skull Creek Formation is primarily dominated by bed-load deposition, although the presence of suspension deposition—recorded only at times—in various facies suggests that quieter conditions occurred across all depositional areas. Even the interlobe deposits are significantly influenced by bed-load transport. Furthermore, the boundaries between the three depositional areas—lobe-fringe, medial inter-lobe, and distal inter-lobe areas—are not clearly defined and are regarded as transitional rather than firm. While unique facies mark each zone, the presence of overlapping facies across these zones makes it challenging to distinguish them clearly.
Open Access
Subsurface mapping of the Ross Island flexural basin, southwest Antarctica
(Colorado State University. Libraries, 2016) Wenman, Christopher P., author; Harry, Dennis, advisor; Egenhoff, Sven, committee member; Gooseff, Mike, committee member
Ross Island is a post-Miocene (< 4.6 Ma) volcanic island located in the Ross Sea region of southwest Antarctica. This region of Antarctica borders the western edge of the West Antarctic Rift System, along the Transantarctic Mountain front. Marine and over-ice multi-channel seismic reflection surveys and borehole studies targeting the Ross Sea region over the last 30+ years have been used in this study to develop a seismic stratigraphic model of the development and evolution of the Ross Island flexural basin. Four key stratigraphic horizons were identified and mapped to fully capture the basin-fill, as well as strata lying above and below the flexural basin. From oldest to youngest these horizons are named RIB-m, RIM-g, RIM-b and RIB-r. Time structure, isochron and isochore maps were created for the horizons and the stratigraphic intervals they bound. The seismic stratigraphic record shows the Ross Island flexural moat formation post-dates the main tectonic subsidence phase within the Victoria Land Basin. The maps presented here are the first to fully illustrate the evolution of the Ross Island flexural basin. The maps highlight depositional patterns of two distinct periods of flexural subsidence and basin-filling superimposed on the older N-S trending Victoria Land Basin depocenter. Two units of flexural basin fill, Unit FFI between horizons RIM-g and RIM-b (the oldest flexural basin fill), and Unit FFII between horizons RIM-b and RIB-r (the youngest flexural basin fill) are associated with the two periods of flexural subsidence. Flexural moat subsidence and subsequent filling occurred episodically during periods of active volcanism on the island. Unit FFI is estimated to range from ca. 4 to 2 Ma, corresponding with formation of the Mt. Bird volcanic edifice on Ross Island. Unit FFII ranges in age from ca. 2 to 1 Ma, and is related to Mt. Terror, Mt. Erebus, and Hut Point Peninsula volcanism. The isochore maps suggest the depocenter of the flexural basin during both time intervals was located north of the island, instead of directly beneath the Ross Island topographic load. Factors contributing to the northerly location of the depocenter include i) volcanic loading by McMurdo Volcanic Group subsea volcanic features north of the island, ii) partial compensation of the main Ross Island load by low-density, partially molten rock beneath the island, iii) extensional faulting within the Terror Rift, and iv) seaward-thickening shelf sediments transported from the Ross Ice Shelf. The seismic data show that the onset of filling of the flexural moat around Ross Island coincided with the end of ice grounding events in the area. We infer that this was caused by flexural subsidence of the seafloor to accommodate the Ross Island load.
Open Access
Timing and genesis of fractures in the Niobrara Formation, northeastern Front Range and Denver Basin, Colorado
(Colorado State University. Libraries, 2010) Allen, Cody Lee, author; Erslev, Eric A., advisor; Charlie, Wayne A., committee member; Egenhoff, Sven, committee member; Richter, Bryan, committee member
Naturally-occurring fractures in foreland basins, particularly in self-sourced resource plays, are critical to the production of hydrocarbons from low permeability reservoirs. Both shear and extensional fractures commonly cause reservoir anisotropy as well as providing critical tests of tectonic hypotheses. The objective of this research is to determine the mechanisms and timing of naturally-occurring fractures in the upper Cretaceous Niobrara Formation along the northeastern Front Range and in the Denver Basin of the Rocky Mountain Foreland. Previous hypotheses for the origin of fractures within the Denver Basin have focused largely on mechanisms invoking basement reactivation either by vertical block motion or by Laramide subhorizontal shortening. Contrasting hypotheses include multidirectional slip, regional and/or local detachment, and post-Laramide extension in the direction of previous compression. This study analyzes the kinematics, modes and mechanisms of deformation in the Niobrara Formation from fractures examined along the northeastern Front Range and from faults identified in 3D seismic data from the Denver Basin. Surface fracture data collected from 61 locations include minor faults, joints, calcite-filled fractures, and pressure solution stylolites. Subsurface data includes two 3D seismic surveys (Sooner Field and Dana Point) were fault geometries were examined. In outcrops, ideal σ1 analysis of strike–slip and thrust fault data document a subhorizontal Laramide compression with an average attitude of 086°-08°. Normal faults identified through the study are highly variable with an average slip direction of 183°- 73°. Normal dip-slip reactivation of right-lateral shear planes indicates normal faults are younger. Two joint systems are observed throughout the study area with J1 joints averaging 078° and later J2 joints averaging 171°. Subsurface 3D seismic data show listric and planar normal fault sets cut the Niobrara and lower Pierre formations. Calculated fault dip angles at Sooner Field average 8°, and those at Dana Point average 27°. These low fault dip angles suggest layer-parallel detachment, but diverse fault strikes are problematic and suggest multiple slip directions. No basement-to-Cretaceous faults were identified in either volume, casting doubt on basement reactivation hypotheses. Fracture sets in the Niobrara Formation show evidence for four different fracture mechanisms. Initial faulting generated by Laramide subhorizontal compression (086°) was followed by later, but still Laramide, ENE- to E-W-striking J1 splitting joints. Post- Laramide extension is indicated by NNW to N-S-striking J2 joints. Lastly, low-angle listric and planar normal faults in seismic data are interpreted to be post-Laramide. They were probably caused by local detachment, but their mechanisms and timing require further investigation.