Stratigraphy and source rock analyses of the Heath Formation in Fergus, Garfield, Golden Valley, Musselshell, Petroleum, and Rosebud counties, central Montana

<p> Three-dimensional fluid-flow simulation models provide attractive tools for understanding the potential behavior of the subsurface. Retention of high-resolution geologic heterogeneity in the characterization of large volumes presents significant challenges to this modeling. </p><p> A 2D dataset donated by Industry constrains a hierarchical stratigraphic framework based on 30,000 wells with log curves, 60 surfaces crossing the 70,000 cubic-kilometer Powder River Basin from Precambrian basement to top of the Cretaceous Lewis Shale. Five sedimentary systems subdivided into 25 stratigraphic intervals make up the 3D representation of 70 discrete modeling areas. These sedimentation regions group distinct sedimentary attributes (e.g., porosity, thickness, sedimentary architecture). These attributes relate to suites of rock properties, such as porosity, percentage of thickness with porosity and well log shape, which were compiled from 4000 wells with donated/purchased log ascii files, 15 cores, 300 wells with public core plug data, 115 published oil field reports, and basin rimming outcrops. </p><p> Sedimentary system analysis considered regional controls on the depositional setting from the craton-scale to the pore-scale and it employed techniques to group information and replicate the effect of fine-scale geologic heterogeneity in a static reservoir model. This process highlights the importance of understanding the role of tectonic anisotropy on the preservation of stratigraphic sequences when interpreting the depositional environment. Subdivision into the 70 sedimentation regions permitted calculation of the gross pore volume in each sedimentary system, using total porosity and a percentage of the vertical thickness for each modeling volume. The total volume calculated depended on the method; stratigraphic layering and sedimentation regions provided 600 cubic kilometers and equating to storage capability of over 250 gigatons of supercritical carbon dioxide, whereas using factors and no stratigraphy, the total volume was calculated at 460 cubic kilometers. </p><p> Pore volume distribution in the subsurface is more accurately characterized with high-resolution stratigraphic and sedimentation region analysis. Integrated tectonic analysis provides context that better constrains the application of outcrop analogs and depositional models, which guide sedimentation region analysis. This dissertation addresses the impact of geologic heterogeneity from crustal anisotropy to distributions of porosity and permeability and provides a tool to assess feasibility of gigaton-scale carbon dioxide sequestration. </p>

<p> Three studies on Cordilleran foreland basin deposits in the western U.S.A. constitute this dissertation. These studies differ in scale, time and discipline. The first two studies include basin analysis, flexural modeling and detailed stratigraphic analysis of Upper Cretaceous depocenters and strata in the western U.S.A. The third study consists of detrital zircon U-Pb analysis (DZ U-Pb) and thermochronology, both zircon (U-Th)/He and apatite fission track (AFT), of Upper Jurassic to Upper Cretaceous foreland-basin conglomerates and sandstones. Five electronic supplementary files are a part of this dissertation and are available online; these include 3 raw data files (Appendix_A_raw_isopach_data.txt, Appendix_C_DZ_Data.xls, Appendix_C_U-Pb_apatite.xls), 1 oversized stratigraphic cross section (Appendix_B_figure_5.pdf), and 1 figure containing apatite U-Pb concordia plots (Appendix_C_Concordia.pdf).</p><p> <b>Appendix A</b> is a combination of detailed isopach maps of the Upper Cretaceous Western Interior, flexural modeling and a comparison to dynamic subsidence models as applied to the region. Using these new isopach maps and modeling, I place the previously recognized but poorly constrained shift from flexural to non-flexural subsidence at 81 Ma.</p><p> <b>Appendix B</b> is a detailed stratigraphic study of the Upper Cretaceous, (Campanian, ~76 Ma) Sego Sandstone Member of the Mesaverde Group in northwestern Colorado, an area where little research has been done on this formation.</p><p> <b>Appendix C</b> is a geo-thermochronologic study to measure the lag time of Upper Jurassic to Upper Cretaceous conglomerates and sandstones in the Cordilleran foreland basin. The maximum depositional ages using DZ U-Pb match existing biostratigraphic age controls. AFT is an effective thermochronometer for Lower to Upper Cretaceous foreland stratigraphy and indicates that source material was exhumed from >4&ndash;5 km depth in the Cordilleran orogenic belt between 118 and 66 Ma, and zircon (U-Th)/He suggests that it was exhumed from &lt;8&ndash;9 km depth. Apatite U-Pb analyses indicate that volcanic contamination is a significant issue, without which, one cannot exclude the possibility that the youngest detrital AFT population is contaminated with significant amounts of volcanogenic apatite and does not represent source exhumation. AFT lag times are &lt;5 Myr with relatively steady-state to slightly increasing exhumation rates. Lag time measurements indicate exhumation rates of ~0.9->>1 km/Myr.</p>

<p> Foreland and forearc basins are large sediment repositories that form in response to tectonic loading and lithospheric flexure during orogenesis along convergent plate boundaries. In addition to their numerous valuable natural resources, these systems preserve important geologic information regarding the timing and intensity of deformation, uplift and erosion history, and subsidence history along collisional margins, and, in ancient systems, may provide more macroscopic information regarding climate, plate motion, and eustatic sea level fluctuations. This thesis presents two studies focused in the Paleozoic Appalachian foreland basin system along the eastern United States and in the Mesozoic to Cenozoic Matanuska forearc basin system in south-central Alaska. </p><p> Strata of the Appalachian foreland basin system preserve the dynamic history of orogenesis and sediment dispersal along the east Laurentian margin, recording multiple episodes of deformation and basin development during Paleozoic time. A well-exposed, >600 m thick measured stratigraphic section of the Pine Mountain thrust sheet at Pound Gap, Kentucky affords one of the most complete exposures of Upper Devonian through Middle Pennsylvanian strata in the basin. These strata provide a window into which the foreland basin's development during two major collisional events known as the Acadian-Neoacadian and the Alleghanian orogenies can be observed. Lithofacies analysis of four major sedimentary successions observed in hanging wall strata record the upward transition from (1) a submarine deltaic fan complex developed on a distal to proximal prodelta in Late Devonian to Middle Mississippian time, to (2) a Middle to Late Mississippian carbonate bank system developed on a slowly subsiding, distal foreland ramp, which was drowned by (3) Late Mississippian renewed clastic influx to a tidally influenced, coastal deltaic complex to fluvial delta plain system unconformably overlain by (4) a fluvial braided river complex. Four samples of Lower Mississippian to Middle Pennsylvanian sandstone were collected from the hanging wall (n = 3) and footwall (n = 1) of the Pine Mountain thrust sheet at Pound Gap to determine sediment provenance in this long-lived foreland basin system. Paleocurrent indicators considered in the context of the regional foreland basin system suggest transverse regional drainage during the development of Early and Late Mississippian delta complexes. Eustatic fall during the early stages of the Alleghanian orogeny to the east saw a shift in regional drainage with the development of a southwestward-flowing and axial braided river system in Early Pennsylvanian time followed by Middle Mississippian transgression of a fluvio-deltaic complex. Detrital zircon U-Pb age data from Lower Mississippian to Lower Pennsylvanian sandstone support regional interpretations of sediment sourcing from probably recycled foreland basin strata along the east Laurentian margin, whereas compositionally immature Middle Pennsylvanian sediment was sourced by a limited distribution of east Laurentia sources reflecting thrust belt migration into the adjacent foreland basin system during Alleghanian orogenesis. </p><p> In addition, the stratigraphy of the foreland basin system in the central Appalachian basin is significantly different compared to the stratigraphic record that is typified for foreland basin systems and suggests that the Carboniferous Appalachian foreland basin system investigated in this study does not fit the typical foreland basin model that is used widely today for both ancient and modern systems. Possible factors that produce the observed discrepancies between the central Appalachian and typical foreland basin systems may include differences in the timing, type, and frequency of orogenic events leading to foreland basin development, related variations in the rheology of the underlying lithosphere, and whether forebulge migration is mechanically static or mobile. </p><p> The Cordilleran margin of south-central Alaska is an area of active convergence where the Pacific plate is being subducted at a low angle beneath the North American plate. In the Matanuska Valley of south-central Alaska, the geology of the Mesozoic to Cenozoic Matanuska forearc basin system records a complex collisional history along the margin from Cretaceous to Miocene time and provides an opportunity to study how shallow-angle subduction affects upper plate processes. Paleocene-Eocene low-angle subduction of an eastward migrating spreading ridge and Oligocene oceanic plateau subduction caused uplift, deformation, and slab window magmatic intrusion and volcanism in the Matanuska Valley region, thereby modifying the depositional environment and structure of the forearc system. In this study, detailed field mapping in the Matanuska Valley region and structural analysis of Paleocene-Eocene nonmarine sedimentary strata are utilized to better understand the structural response of the forearc basin system to multi-stage flat-slab subduction beneath an accreted continental margin, a process observed along multiple modern convergent margins. Four geologic maps and structural cross-sections from key areas along the peripheries of the Matanuska Valley area and one regional cross-section across the forearc system are presented to delineate its local structural configuration and to contribute to a more complete understanding of how sedimentary and tectonic processes along modern convergent margins may be or have been impacted by shallow-angle type and related subduction processes.</p>

<p> Two industry acquired diatomite cores (Sisquoc Formation) from the Orcutt (Newlove 76-RD1) and Casmalia Hills (Stokes A-30804) oil fields were analyzed by core descriptions, laboratory analysis (XRD and SEM), and gamma ray logs. Based on these data, five distinct lithofacies, nine sedimentary features and compositional trends of both cores were established. Newlove 76-RD1 and Stokes A-30804 record an upward-shallowing succession at different depositional positions on the Pliocene paleo-slope of the Santa Maria basin. Stokes A-30804 reflects slope deposition on a lower flank of a paleo-bathymetric high receiving higher detrital influx from inter-ridge troughs. Slope deposition of Newlove 76-RD1 was closer to a paleo-bathymetric high where purer diatomaceous sediments accumulated. Within Stokes A-30804, purer opal-A dominant lithofacies contain the highest oil saturations. The diagenesis and precipitation of opal-CT and abundance of phyllosilicate significantly hinders oil saturation within lithofacies.</p>

<p> Petrography and phase equilibria involving the minerals trona (Na₂CO₃&bull;NaHCO₃&bull;2H₂O), nahcolite (NaHCO₃), and shortite (Na₂CO₃&bull;2CaCO₃) from the Eocene Green River Formation provide information on the paleoenvironments that controlled their formation during deposition and diagenesis. Shortite and trona are exclusive to the Wilkins Peak Member (WPM) of the Bridger Basin (BB), WY, whereas nahcolite is the primary Na-carbonate mineral in the contemporaneous Parachute Creek Member of the Piceance Creek Basin (PCB), CO. Trona from the BB and nahcolite from the PCB are stratigraphically associated with oil shale, suggesting deposition in perennial, density stratified saline lakes. Preserved primary textures of trona and nahcolite show that they formed at the air-water interface as microcrystalline chemical muds, which supports the hypothesis that precipitation occurred in contact with the early Eocene atmosphere. New experiments (temperature vs. <i>p</i>CO₂) in the NaHCO₃ -Na₂CO₃-CO₂-H₂O system show that nahcolite forms at a minimal <i>p</i>CO₂ concentration of ~ 680 ppm at 19.5 &deg;C, 1 atm, which is lower than the <i>p</i>CO₂ determined by Eugster (1966) (1330 ppm and 1125 ppm with NaCl added). These new results anchor the minimum <i> p</i>CO₂ of the early Eocene atmosphere at ~ 680 ppm. </p><p> Shortite formed diagenetically during burial in the BB as displacive crystals, fracture fills, and pseudomorphous replacements of a precursor Na-Ca-carbonate in carbonate mudstone and oil shale. Experimental results on the thermal stability of shortite in the Na₂CO₃-CaCO₃-H₂O system show that it forms at temperatures > 55 &deg;C, 1 atm, and 1.1m Na₂CO3 via the reaction: Na₂CO₃&bull;CaCO₃&bull;2H₂O_(pirssonite) + CaCO_3(calcite) = Na₂CO₃&bull;2CaCO_3(shortite) + 2H₂O. The large area over which shortite occurs in the WPM indicates saline pore fluids existed in the buried lacustrine sediments and that, at times, giant Na-CO₃-rich saline alkaline lakes existed in the BB during WPM time. The thermal stability of shortite, coupled with vitrinite reflectance data and inferred regional geothermal gradients, establish that the WPM was buried to depths of ~ 1,500 m and experienced post WPM erosion of ~ 800 m.</p>

<p> Though the Cotton Valley Group is productive in Mississippi, Louisiana, and Texas, little is known about production potential of the Bossier Formation (Lower Cotton Valley Shale) in southwest Mississippi. The Bossier Formation in Jefferson County, Mississippi is an organic-poor, carbonate-rich mudrock with siliciclastic intervals. Examination of cuttings by petrographic and scanning electron microscopy revealed fractures that have been filled by calcite and pore-filling pyrite. Porosity exists within and around pyrite framboids, in unfilled fractures, and within peloid grains. Organic matter is rare in Lower Cotton Valley samples suggesting it is not self-sourcing. Total Organic Carbon (TOC) values are low (0.86-1.1% TOC) compared to the productive Haynesville Shale Formation (2.8% TOC). Porosity of the Lower Cotton Valley Shale is low (2.5-4.2%) compared to productive Haynesville Shale Formations (8-12%). With current technology and gas prices, the Lower Cotton Valley Shale in Jefferson County, Mississippi does not have production potential.</p>

Thesis (B.Sc.(Hons.)) -- University of Adelaide, Dept. of Geology, 1972. / Typescript (photocopy).

Thesis (Ph. D.)--Johns Hopkins University, 1913. / Biography. Reprinted from vol. 1 of Upper Cretaceous, pub. by the Maryland geological survey.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1950. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 170-177).