Browsing by Author "Egenhoff, Sven, advisor"
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Item Open Access Depositional environment and facies architecture of the Lower to Middle Ordovician carbonate ramp succession, Öland, southern Sweden(Colorado State University. Libraries, 2014) Cigri, Ali Riza, author; Egenhoff, Sven, advisor; Ridley, John, committee member; Çavdar, Gamze, committee memberThe Lower to Middle Ordovician carbonates of Öland, southern Sweden, exhibit outcrops of up to 12 m thickness and rest conformably on Cambrian black shales of the Alum Formation. Based on lithological and sedimentological characteristics, nine carbonate facies were identified within the successions that are grouped into four facies associations (FAs). FA 1 is composed of glauconite- bearing mud- to wackestone facies. FA 2 consists of three glauconite- and one glauconite- and Fe-ooid bearing mud- to packestone carbonate facies. Deposits of FA 3 are carbonate mud- to wackestone facies. FA 4 is characterized by one Fe- ooid bearing and four other mud- to packstone carbonate facies. The studied carbonate succession is subdivided into three stratigraphic units referred to as Intervals 1 to 3. Interval 1 consists of the Köpingsklint and Bruddesta Formations located at the base of the succession. Interval 2 is composed of the Horns Udde formation in the middle level of the succession, and Interval 3 is characterized by the Gillberga Formation situated at the top of the succession. FA 1 rocks were deposited in an offshore proximal setting, whereas FA 2 records an offshore distal setting during "starved" times. FA 3 and FA 4 rocks were deposited during the "normal" times reflecting offshore proximal and distal settings, respectively. Heterozoan assemblages, allochthonous Fe- ooids, and abundance of carbonate mud within the facies suggest that the studied carbonate succession experienced temperate to sub-tropical sea-water conditions during deposition despite its paleo-latitudes equivalence to what would be temperate to cool-water environments of modern examples. Three 3rd order sequences having regressive systems tracts (RSTs) and transgressive systems tracts (TSTs) bounded by maximum regressive surfaces (MRSs) were determined within the studied succession based on the transgressive versus regressive sequence stratigraphic model. The MRSs are situated at the top of the RSTs reflecting maximum sea-level drops. Interval 1 is interpreted to represent both TST and RST characterized by glauconite-bearing facies, and have a sequence boundary (MRS) at the base. Interval 2 contains two sequence boundaries (MRSs) and is comprised of two TST and one RST characterized by carbonate facies. Interval 3 has a sequence boundary (MRS) at the top and is composed of one RST discriminated by glauconite-bearing facies. The Lower to Middle Ordovician carbonates and their subsurface equivalence have high potential in terms of conventional and unconventional petroleum exploration based on their lithologic character and positions in the Paleozoic petroleum system in the Baltic Sea of Scandinavia and adjacent areas.Item Open Access Diagenesis, composition and porosity of the upper Three Forks Formation, Williston basin, North Dakota and Montana(Colorado State University. Libraries, 2014) Kolte, Ketki, author; Egenhoff, Sven, advisor; Ronayne, Michael, committee member; Paschke, Mark, committee memberThe upper part of the Three Forks Formation in the Williston basin of North Dakota and Montana is one of the prime targets for oil exploration in the onshore part of the US today. The unit is mainly composed of dolomite, yet the details of dolomite formation and its relative timing are unknown. This study is the first that combines an analysis of cement generations and porosity to develop a diagenetic scheme based on detailed microscopical observations. The upper Three Forks Formation shows a total of seven dolomite generations along with some anhydrite and pyrite. Most of the rock consists of an inclusion-rich dolomite, likely dolomite II, that forms mm- to sub-mm-size rhombic crystals showing overgrowth of five more alternating clear and inclusion-rich dolomite generations, and in places a core of iron-rich dolomite I. Porosity types in the upper Three Forks Formation are intercrystalline, intracrystaline, and "moldic" which here stands for the dissolution of entire dolomite crystals. Detrital components are quartz, feldspars, mica, and clay particles. The Three Forks Formation was most likely deposited on a mixed carbonate-siliciclastic ramp as a limestone unit with varying amounts of detrital input. Initial replacement of limestone into dolomite probably occurred early entirely changing the texture of this unit. Several dolomite phases occurred during burial post-dating early dolomitization. The effective porosity, characterized by intercrystalline and "moldic" pores, is linked to the dolomitization, most likely originally to an early event as no late dolomite is seen filing these pores. Up to centimeter-size voids, though, representing mostly non-effective porosity is generally partly filled with several generations of dolomite and leaving some part of the vugs open. This indicates that most likely the voids were formed before the last few generations of dolomite cement, and also that not all open space was easily occluded by these dolomitizations but left some of the porosity untouched. Based on a limited data set, porosity distribution in the upper Three Forks Formation does not show a clear link to the distribution of dolomite. However, it does show a trend to overall increased values from the east (less than 1%) to the west (around 5%) with a north-south extending zone of maximum porosities (about 10-12%) around 103.5°. It is therefore likely that potential hot spots in this basin are rather located in western ND while towards the east porosities are lower.Item Open Access Enhanced recovery from ancient carbonate ramps: lessons and analogs from Paleozoic successions and the Persian Gulf(Colorado State University. Libraries, 2009) Jaffri, Ali R., author; Egenhoff, Sven, advisorSatellite imagery of the Persian Gulf, fieldwork in Kuwait and Abu Dhabi, and data from published sources are integrated to develop a thorough understanding of large-scale stratal architecture in carbonate ramps. A section of this study deals with the identification of key-surfaces in homogeneous successions. An Ordovician carbonate ramp from Sweden is selected to illustrate the importance of trace fossils in identification of maximum regression surfaces. By comparing Ordovician trace fossils from Sweden with modern crab burrows in Kuwait, a sequence stratigraphic model that shows strata architecture is presented. Oolitic facies in ancient carbonate ramps in the Devonian-Mississippian Bakken Formation that have been previously ignored or considered subtidal sheet-like deposits have been reinterpreted as coastal embayment, eolian dunes on barrier islands, and tidal channel deposits. Geometric analyses of similar environments in the modern Persian Gulf reveal that none of the oolitic facies in the Bakken Formation would be conducive to a sheet-like morphology. This paper highlights the diversity in shapes and dimensions of modern oolitic tidal channels in the Persian Gulf. Tidal channels documented in satellite imagery are oriented parallel, perpendicular or oblique to the shoreline. Planforms are remarkably similar to terrestrial fluvial systems, and transitions between straight, meandering, anastomosing, and braided patterns occur. Wide, straight channels form where bank materials consist of non-cohesive oolitic-skeletal sands, whereas those with prolific cyanobacterial growth along banks are prone to sinuous channels. A section investigates the challenges that oil and gas companies face when attempting to strike a balance between appeasing authorities and exploiting hydrocarbons while maintaining sustainable development. It also recommends policies that include amendments regarding oil fields in Kurdish territory and healthy alternatives to Production Sharing Agreements which ensure the flow of oil from Iraq while maintaining sustainable development. These include exclusion of oil fields in the Kurdish territory, which constitute only 3 percent of Iraq's oil reserves, from article 5a of the Iraqi Oil and Gas Law. This study recommends the use of contracts, such as Technical Service Agreements, that satisfy both the foreign oil companies and the Iraqi populace.Item Open Access Facies architecture and depositional processes influencing carbonate facies belt development along a low-inclined shelf, Huk Formation, Norway, and Komstad Formation, Sweden(Colorado State University. Libraries, 2022) Van Hook, James J., author; Egenhoff, Sven, advisor; Stright, Lisa, committee member; Stanley, Michelle, committee memberHeterozoan, or temperate to cool water, carbonate successions can provide unique obstacles to establishing a typical depositional model that can be universally applied. Unlike their tropical realm counterparts, these carbonates are typically highly heterogeneous, occurring across a wide range of oceanographic and climatic settings, thus requiring a case-by-case approach to interpret any given depositional system. One such example is displayed in the Middle Ordovician aged Huk Formation of southern Norway, and Komstad Formation of Scania, Sweden. These formations are approximately 8m thick, corresponding to the Baltoscandian "Orthoceratite Limestone." This study aims to explore the depositional processes influencing the facies development along a temperate-water, low-inclined carbonate shelf environment by characterizing and interpreting two formations along the shelf profile representing varying positions along the transect. The Huk Formation consists of the lower Hukodden Member composed of mostly massive wackestone, a middle Lysaker Member composed of interbedded nodular to semi-nodular wackestone and carbonate mudstone, and an upper Svartodden Member composed of mostly massive packstone and some massive wackestone. The Komstad Formation is composed of an informal lower member, composed of mostly massive wackestone, and an informal upper member composed of interbedded nodular and semi-nodular wackestone and carbonate mudstone with some massive wackestone beds. The facies of these formations can be grouped into seven carbonate facies: massive trilobite- and brachiopod-bearing calcareous mudstone (facies 1), bioturbated carbonate mud-wackestone (facies 2), planar-bedded fossiliferous wackestone (facies 3a), nodular to lenticular fossiliferous wackestone (facies 3b), mud-rich carbonate wacke- to packstone (facies 3c), massive fossiliferous packstone (facies 4a), and fossiliferous carbonate packstone pockets (facies 4b). These facies are ordered by increasing grain size as well as relative grain biodiversity, reflecting an overall increase in energy regime and subsequent decrease in water depth. These facies are further interpreted to represent the various processes and facies development on a low-inclined carbonate shelf, with massive packstones and wackestones occupying the proximal middle shelf environment, thin beds of nodular to semi-nodular wackestone in the distal middle shelf, and carbonate mudstone in the deep shelf environment. Despite the overall decrease in energy regime at depth, the energetic influences on the carbonate facies changes indicate that storms had a prominent impact on their development throughout the succession. This along with the presence of bioturbation and burrowing throughout the succession indicate that even the distal most reaches of this succession was deposited above storm wave base in a well oxygenated and hospitable environment. These formations further reflect a relatively drastic sea-level fall compared to the over- and underlying dark graptolitic shales. Regional sea-level reconstructions identify a largely scale regression during the deposition of these carbonate successions relative to the overlying and underlying graptolitic siliciclastic mudstones, identifying a relative sea-level low point within the middle of the succession at the transition from the Volkhov to the Kunda stage. Paleoenvironmental and paleoclimatic reconstructions of Middle Ordovician Baltoscandia indicate that environmental conditions during this time were generally relatively stable, suggesting that the fine-scale interbedded wackestone and mudstone characteristic of these formations could serve as excellent indicators of the fine- scale climatic and environmental fluctuations.Item Open Access Facies distribution, its implications for climate signals, and hydrocarbon potential of the Permian Lyons Sandstone, Front Range Basin, northern Colorado, USA(Colorado State University. Libraries, 2016) Kendigelen, Oguzhan, author; Egenhoff, Sven, advisor; Stright, Lisa, committee member; Omur-Ozbek, Pinar, committee memberThe Permian Lyons Formation consists of mostly fine- to medium-grained sandstones with minor silt- and mudstone intercalations. The formation shows six siliciclastic facies that are grouped into two Facies Associations: Facies Association 1 consists of high-angle cross-laminated sandstones (Facies 1), low-inclined cross-laminated sandstones (Facies 2), horizontally-laminated sandstones (Facies 3), and chaotically-bedded to folded sandstones (Facies 4), while Facies Association 2 is mainly characterized by wavy- to irregularly-laminated silty sandstones (Facies 5) and massive to wavy-laminated silt-rich mudstones (Facies 6) with minor amounts of high-angle cross-laminated sandstones (Facies 1), low-inclined cross-laminated sandstones (Facies 2) and horizontally-laminated sandstones (Facies 3). Facies Association 1 deposits dominate the southern part of the study area whereas Facies Association 2 sediments are more common towards to north. Stratigraphically, Facies Association 1 and 2 deposits occur intercalated with each other, and generally show two time Facies Association 2 sediments overlain by Facies Association 1 deposits. This intercalation of Facies Associations is best observed in the central part of the study area. In the south, Facies Association 1 deposits strongly dominate the succession, and in the north Facies Association 2 deposits are much more common, and do not show intercalation clearly. In the Lyons Formation, high-angle cross-laminated sandstones (Facies 1) are interpreted as remnants of fossil eolian dunes. Between these dunes, nearly flat to low-inclined dry interdunal areas occur and they are characterized by low-inclined cross-laminated sandstones (Facies 2) and horizontally-laminated sandstones (Facies 3). Chaotically-bedded to folded sandstones (Facies 4) represent internal deformation of dune deposits in the lower portion of dune flanks. Deposition of wavy- to irregularly-laminated sandstones (Facies 5) reflects wet to damp conditions in interdune areas. Massive to wavy-laminated silt-rich mudstones (Facies 6) indicate the presence of small ponds or lakes between dunes. Facies Association 1 deposits overall represent dry eolian conditions, and Facies Association 2 deposits represent wet eolian conditions. The distribution of Facies Association therefore indicates that dry and wet climates were generally alternating but overall dry climate conditions dominated the southern part of the study area whereas wet conditions were more prevalent in the north. Stratigraphically, the north to south transect reflects an expansion of dry conditions northwards despite the climate fluctuations, and a “Goldilocks” window of where to best observe climate cycles in the central part of the study area. This change in depositional conditions is exclusively observed along a north-south transect but not evident in an east-west direction. This study interprets the parts of the succession where Facies Association 1 sediments dominate as the paleo-erg center, and the portions where wet Facies Association 2 deposits are more prevalent as a paleo-erg margin environment. In the Lyons Formation, dry eolian deposits show good reservoir quality because of overall excellent sorting and roundness of the grains, while wet eolian deposits contains more fine-grained sediment which causes poorly sorting and reduction of porosity. Therefore, this study interprets that the main Lyons Formation plays are in the southern part of the study area within the paleo-erg center where dry eolian deposits are strongly dominating.Item Open Access Facies reconstruction and detrital zircon geochronology of the Ingleside/Casper Formation(Colorado State University. Libraries, 2018) Nair, Kajal, author; Egenhoff, Sven, advisor; Singleton, John, advisor; Rocca, Monique, committee memberMixed siliciclastic-carbonate deposits of the Ingleside/Casper Formation in northern Colorado and southeastern Wyoming developed along the flanks of the Ancestral Front Range during the Late Paleozoic. This study establishes a sedimentological model for the Ingleside/Casper Formation along with using detrital zircon data to identify siliciclastic sediment sources for Late Paleozoic deposits in two Ancestral Rocky Mountain basins along the Ancestral Front Range and Uncompahgre Highlands. The stratigraphic successions of the Ingleside/Casper Formation display a diverse suite of carbonate and siliciclastic lithofacies in close lateral and vertical association with each other. The six different siliciclastic facies and their subfacies identified in this study include: (1) cross-bedded sandstone (tabular cross-bedded sandstone and trough cross-bedded sandstone), (2) horizontally-bedded sandstone, (3) massive sandstone, (4) conglomeratic sandstone, (5) ripple-laminated sandstone (asymmetric current ripples, moderately-steeply climbing ripples, and gently climbing ripples), and (6) silt-rich siliciclastic mudstone. The three different carbonate facies and their subfacies identified in this study include: (1) carbonate mudstone-wackestone, (2) carbonate packstone (packstone with non-skeletal grains and packstone with bioclasts), and (3) carbonate grainstone (grainstone with non-skeletal grains and grainstone with bioclasts). Thinning and/or pinching out of carbonate facies accompanied with a gradual increase in siliciclastic sedimentation is observed laterally across the study area from north to south. Eight stratigraphic intervals are recognized from correlations across a north-south transect of 120 km and each interval displays a lithofacies assemblage dominated either by carbonates or siliciclastics. Both carbonate and siliciclastic successions display small-scale fining-upward trends, with coarsening-upwards being partially or wholly absent across the study area. One of the eight intervals (termed Interval 6) is of significant interest in this study because it displays a unique lithofacies assemblage, with it being the only interval where trough cross-beds of facies 1B occur. Overall, carbonate units vary in the extent to which they onlap onto siliciclastic strata throughout the succession: Intervals 1 to 4 record a successive advance of onlap towards the south, whereas intervals 5 to 8 record a retreat of onlap and a successive northwards migration of carbonate strata. The nine different lithofacies and their subfacies identified in this study represent an array of shallow-marine paleoenvironments that include foreshore, shoreface, offshore transition, and offshore, and terrestrial settings comprising coastal eolian dunes and fluvial systems. Stratigraphic distribution of facies suggests that deposition in a shallow-marine environment alternated between dominantly siliciclastic and dominantly carbonate, mainly as a result of fluctuations in the input of siliciclastic sediment and its effect on carbonate deposition. In a distal direction, both siliciclastic and carbonate facies graded into carbonate mudstone that is identified as the most distal setting across all stratigraphic successions studied here. The Ingleside/Casper succession is interpreted to consist of two superimposed scales of sea-level fluctuations with the small-scale cycles represented by deepening-upwards successions across the study area, and a superimposed large-scale sea level curve recorded in the varying onlap of carbonates. The superimposed curve shows an overall transgression in the lower part of the succession succeeded by a regression in the upper part. Independent of this type of sea-level curve, dry eolian dunes dominated the stratigraphic record during Interval 6 and reflect a sharp change in climate to more arid conditions that accompanied the exclusive formation of dunes during this time. The sedimentological study suggests that deposition of the Casper/Ingleside Formation was governed by the two orders of sea-level oscillations and also climate change, both operating on two separate scales. The general fall in sea level and increase in aridity in the upper Ingleside/Casper Formation is attributed to the onset of a major Gondwanan glaciation phase that culminated during the Pennsylvanian-Permian transition which is likely to be located at the very top of this unit. Based on exclusively sedimentological considerations, this study therefore suggests that the Ingleside Formation, which is typically assigned a Permian age, was most likely deposited during the Late Pennsylvanian. This interpretation is also based on the correlation of the Coloradoan Ingleside Formation to the Casper Formation in Wyoming that contains a known Late Pennsylvanian fussuline assemblage. This study also presents new detrital zircon U-Pb geochronology data from the type section of the Ingleside Formation at Owl Canyon, and the Molas and Hermosa Formations near Molas Lake to understand Late Paleozoic sediment provenance and dispersal patterns across Colorado. U-Pb ages on 120-150 zircons were determined from each sample using LA-ICPMS, and ages with excessive discordance (>20% discordant or <5% reverse discordant) were rejected. All samples contain between 5% and 10% concordant Paleozoic aged zircons ranging from 330-490 Ma. Other significant age distribution peaks identified range between 990-1200 Ma, 1340-1500 Ma, 1600-1800 Ma, and 2500-3500 Ma. The wide spread of zircon age populations record a mixed Laurentian derivation comprising local and distal sediment sources. Paleozoic-age zircons are interpreted to coincide with high magmatic flux during the Taconic and Acadian orogenies in the Appalachian orogen. The diverse components in the U-Pb age data suggest that a widespread sand-dispersal system that transported local and distant sediment sources along the Ancestral Rockies was operational during the Late Paleozoic. Areas of eolian recycling observed in the Ingleside and Molas Formations points towards eolian systems playing an important role in transportation of distally-sourced zircons during Late Paleozoic time. Additionally, the U-Pb detrital zircon data indicate that a shift from non-marine to marine deposition across the Fountain-Ingleside transition was accompanied by a decrease in locally-sourced detrital zircons, most likely marking the cessation of Ancestral Front Range uplift. Conversely, the shift from non-marine to marine deposition across the Molas-Hermosa contact was accompanied by an increase in locally-sourced detrital zircons, most likely marking the initiation of the Uncompahgre uplift.Item Open Access False Bakken' interval- sediment patterns and depositional architecture at the facies boundary between siliciclastic mudstones and carbonates, Lodgepole Formation, Mississippian in the Williston Basin, ND(Colorado State University. Libraries, 2020) Spansel, Joel, author; Egenhoff, Sven, advisor; Sutton, Sally, committee member; von Fischer, Joe, committee memberThe lateral facies transition on deep shelves between carbonates and siliciclastic mudstones is largely enigmatic. Based on detailed facies descriptions and interpretations, this study explores which processes have shaped the sedimentary rocks on both sides of this lithological divide, and adds to our understanding of processes operating on deep shelves in general. Both siliciclastic and carbonate rocks of the 'False Bakken' and 'Scallion' intervals of the lower Lodgepole Formation in the Williston Basin, ND, can be grouped into twelve facies: these facies are graded argillaceous mudstone (F1), massive siliciclastic-argillaceous mudstone (F2a), massive calcareous-argillaceous mudstone (F2b), bioturbated pyrtitized bioclast-bearing mudstone (F3), lenticular mudstone (F4), bioclast-rich wavy mudstone (F5), siliciclastic siltstone (F6), glauconitic siltstone (F7), calcareous siltstone (F8), massive to bioturbated carbonate mudstone (F9), nodular skeletal wackestone (F10), and laminated skeletal packstone (F11). These facies are here presented in order of increasing grain size, carbonate content, and bioturbation from F1 to F11. They are arranged in three fining- and coarsening-upward units that can be identified throughout the basin within the succession. These twelve facies are interpreted to represent distinct processes on a low-inclined shelf system with carbonate occupying the proximal, and siliciclastic mudstones the distal portions of this transect. An overall decrease in energy is reflected from the proximal carbonate to distal siliciclastic facies in this sedimentary system. Nevertheless, most of the mudstone facies still reflect high energy processes operating within the distal portions of the basin; in fact, only one mudstone facies is interpreted to reflect suspension settling under tranquil conditions. Therefore, this study suggests that storm wave base is best placed within the distal siliciclastic mudstones instead of in the proximal carbonates. Carbonate mudstones, deposited above storm wave base but lacking tempestite deposition are therefore interpreted as having been subject to intense degradation of storm-derived bioclasts. A decrease in oxygen concentration is inferred from proximal carbonates to distal siliciclastics as indicated by the decrease in size and type of burrows; yet, the presence of burrows within the most distal facies belt indicates that at least dysoxic conditions prevailed throughout the Williston Basin during the deposition of the 'False Bakken'. Three transgressions and regressions are identified within this succession based on laterally correlated facies patterns and indicate an overall increase in sea level from the beginning to the end of 'False Bakken' times. Sediment starvation occurred in the northeastern and/or southwestern portions of the basin as indicated by the presence of glauconitic siltstones and/or lenticular mudstones at various locations within the succession. However, a source of sediment input is interpreted to be located in the northwestern part of the basin based on a high abundance of detrital silt. In addition, a shift in the basin depocenter southwards from Bakken to lower Lodgepole times is reflected in this succession most likely mirroring an increase in subsidence south of Mountrail County during 'False Bakken' deposition.Item Open Access Hyperpycnal flow deposition and sequence stratigraphy of a Cretaceous near-shore mudstone unit — the Skull Creek Shale Formation, Colorado, USA(Colorado State University. Libraries, 2015) Masterson, Kathleen J., author; Egenhoff, Sven, advisor; Wohl, Ellen, committee member; Stanley, Michelle, committee memberThe middle shale member of the Cretaceous Dakota Group, the Skull Creek Formation (Fm.), is a proximal mudstone unit deposited in a delta-fed system within the Cretaceous Interior Seaway. Based on lithology, sedimentary structures, bioturbation intensity, and TOC values, the Skull Creek Fm. was divided into twelve facies which were grouped into five facies associations (FAs). All facies and FAs record deposition along proximal to distal regions within an ancient mud-dominated continental shelf. Sediment transport and deposition were strongly influenced by both river flooding and storm events that generated hyperpycnal flows. Sediments in the Skull Creek Fm. were transported as bed load by a combination of wave and current energy above storm wave-base (FA 5, FA 4, and parts of FA 5) or exclusively by currents as the flow traveled below storm wave-base (parts of FA 3, FA 2, and FA 1). Mud-rich siltstones and sandstones (FA 4) and bioturbated siltstones and sandstones (FA 5) are the most proximal FAs and were deposited above storm wave-base while ripple- to planar-laminated siltstones and mudstones (FA 3) were interpreted to be "medial" expressions of hyperpycnal flows due to the low occurrence of wave generated structures. The most distal FA’s include massive, bioturbated mudstones (FA 1) that were deposited in a sediment starved area, most likely located laterally or in a more distal location to the laminated mudstones (FA 2). Laminated mudstones (FA 2) were transported as bed load within turbulent flows below storm wave-base. Fining-upward parasequences containing fine-grained FAs (FA 1 and FA 2) represent decreasing energy conditions and a rise in sea level, while stacked successions of more proximal units (FA 3, FA 4, and FA 5) are indicative of high energy levels and lower sea levels. Based on the stacking patterns of the five FAs, the Skull Creek Fm. was divided into five laterally traceable stratigraphic intervals. Transgressive system tracts are observed in interval 1 and interval 2, which are fining-upward successions composed of FA 5, FA 4 at the base and FA 1, FA 2, and FA 3 at the top. Interval 3 contains mainly HCS sandstones and siltstones which thicken vertically and it represents the only highstand system tract (HST) within the Skull Creek Fm. A regressive sequence is preserved in interval 4 which is composed of the most proximal FAs (mainly FA 5) and is abruptly overlain by interval 5, which is a fining-upward succession, and represents a final transgressive system tract within the Skull Creek Fm. TOC (total organic carbon) content is highest, and contains the most oil-prone organic matter, within interval 2 which is composed of mainly laminated mudstones (FA 2). The high TOC values within FA 2 are due to low levels of bioturbation and low levels of sediment accumulation, whereas in other FAs moderate to high bioturbation intensities and high sedimentation rates decrease the likelihood of preserving organic matter. "Sweet spots" within other similar, proximal mudstone units that were deposited as hyperpycnal flows are therefore predicted to be found in distal deposits, where there was limited sediment reworking by organisms.Item Open Access Paleozoic facies architecture in low-inclined mixed carbonate-siliciclastic sedimentary systems: depositional and tectonic signatures(Colorado State University. Libraries, 2019) Novak, Aleksandra, author; Egenhoff, Sven, advisor; Stright, Lisa, committee member; Schutt, Derek, committee member; von Fischer, Joe, committee memberTo view the abstract, please see the full text of the document.Item Open Access Sedimentology and depositional environment of the Middle Ordovician Black Cove and American Tickle Formations - western Newfoundland(Colorado State University. Libraries, 2013) Petrowsky, Matthew J., author; Egenhoff, Sven, advisor; Hannah, Judy, committee member; Borch, Thomas, committee member; Hill, Ronald, committee memberThe Middle Ordovician (Darriwilian) Black Cove (Nicholsonograptus fasciculatus biozone) and overlying American Tickle Formations (Pterograptus elegans biozone) represent the lower portion of the Goose Tickle Group located in western Newfoundland. The succession consists of a total of seven lithofacies, four siliciclastic and three carbonate that are grouped into three distinct facies associations. Facies association 1 (FA1) contains intercalations of clay-rich mudstones (Facies A) with silt-bearing, clay-rich mudstones (Facies B) and in places, foresets of alternating siltstone and clay-rich laminae (Facies C). Facies association 2 (FA2) consists of rocks within FA1 and localized massive, silt-to-sandstones (Facies D). Facies association 3 (FA3) is characterized by carbonate mud-to-wackestones (Facies E), laminated and massive, peloidal, skeletal packstones (Facies F), and skeletal grainstones (Facies G). Each of the three facies associations is interpreted to represent a distinct position on a proximal to distal transect of a shelf that faced the proto-Atlantic. Bedload transport processes are present throughout the succession and are indicated by sedimentary structures such as ripples, planar laminations, mudstone rip-up clasts and lenticular siltstone laminae. These high-energy event deposits likely represent episodically occurring storms and are intercalated into fine-grained fair-weather sediments (Facies A, C, and E). The Black Cove and American Tickle Formations as a whole show an overall shallowing-upward trend that is subdivided into four coarsening-upward parasequences marked by carbonates (FA3) directly overlying fine-grained siliciclastic mudstones (FA1 and FA2). Each of these parasequences is interpreted to represent a lowstand unit attributed to a sea level fall. A comparison with time-equivalent lowstands worldwide suggests that at least two of these lowstands are most likely tectonically-induced. The presence of characteristic shelf sediments showing easily recognized sea level fluctuations, and the absence of turbidites within the Black Cove and American Tickle Formations suggests that these units reflect deposition in a distal shelf environment and not on a lower slope or within a basin as previously suggested. Phycosiphon incertum fecal strings and local Planolites isp. ichnofossils are abundant in the carbonate and fine-grained siliciclastic mudstone facies, providing evidence of dysoxic rather than anoxic conditions during deposition of the Black Cove and American Tickle Formations, allowing benthic burrowing organisms to flourish.Item Open Access Sedimentology and diagenesis of the lower Lodgepole Formation, Williston Basin, North Dakota(Colorado State University. Libraries, 2013) Mackie, James, author; Egenhoff, Sven, advisor; Schutt, Derek, committee member; Rocca, Monique, committee memberThe Scallion and overlying False Bakken intervals represent the lowermost portion of the Mississippian Lodgepole Formation, a predominantly carbonate unit located in the Williston Basin of North Dakota (ND) and Montana (MT) in the US, and Saskatchewan and Manitoba in southern Canada. Macroscopic and microscopic observations allow a subdivision of these mostly fine-grained sediments into five carbonate and two siliciclastic facies. These facies form distinct stratigraphic units that can be traced through western ND and easternmost MT with nodular skeletal wackestones and packstones of the Scallion interval at the base showing a distinct coarsening-upward trend, overlain by between one and three black siliciclastic mudstones with interbedded carbonate mudstones of the False Bakken unit. This lowermost part of the Lodgepole Formation represents mid-ramp to basinal settings of a low-inclination carbonate platform system within the half-enclosed intracratonic Williston Basin. The observed stacking patterns reflect relative sea-level changes that influenced facies distribution within the basin throughout its evolution: the coarsening-upward observed within the Scallion interval shows a general shoaling of the setting during progradation, representing a lowstand systems tract. The False Bakken interval consisting of up to three shale beds with intercalated carbonate mudstones shows a significant fining within the lower Lodgepole Formation depositional system and is interpreted as representing the transgressive systems tract. The subdivision into a maximum of three mudstone units reflects three backstepping parasequences during relative sea-level rise. The subsequent renewed onset of fine-grained carbonate deposition on top of the False Bakken interval reflects deposition during highstand conditions. During burial, the Lodgepole Formation experienced a complex series of diagenetic events with nodule formation, dolomitization, and pressure dissolution being the most prominent. The results of these processes are irregularly distributed both stratigraphically and geographically and play a significant role in reservoir quality of the formation.Item Open Access Sedimentology of an Upper Ordovician (late Katian-Hirnantian) deep shelf mudstone exposure preceding massive sea level drop - Mount Ålleberg, Västergötland, Sweden(Colorado State University. Libraries, 2021) Thomas, Russell, author; Egenhoff, Sven, advisor; Ronayne, Michael, committee member; von Fischer, Joe, committee memberThe deposition of siliciclastic mudstones in a passive margin deep shelf environment has not been explored well in literature. The upper Ordovician succession at Mt. Ålleberg, Västergötland (southern Sweden) is such a succession mirroring sedimentation on Baltica's deep shelf just prior to a catastrophic sea-level draw-down during the Hirnantian Ice Age. The here presented only exposed section is 6.3 meter thick and consists mostly of siliciclastic mudstones interspersed with carbonates. Siliciclastic mudstones are subdivided by dominant clast material and size into four facies, namely fine- to medium-grained (1), carbonate-rich (2), silt- to sand-rich (3), and bioclastic-rich (4). The carbonates are divided into two facies; a carbonate mud- to wackestone (facies 5) seen throughout the section and a lithoclastic fossiliferous carbonate rudstone (facies 6) only observed at the top of the section. Facies 6 carbonate rudstone clasts are poorly sorted and the matrix contains geopetal cement. The idealized succession coarsens upward from facies 1 to facies 5 and excludes facies 6; this idealized succession is observed only once in the section. Siliciclastic mudstones as well as one carbonate (facies 5) contain sediment features and trace fossils of round mud-filled burrows, randomly oriented shells, Phycosiphon-like fecal strings, and generally massive texture. Siliciclastic mudstones are observed with irregular, non-continuous, normally graded laminae. The succession is interpreted as deposition on the low-inclined Baltica shelf reflecting a ramp-like setting mostly an outer shelf environment reaching into a mid-shelf setting. Sediment features and trace fossils are a result of bioturbating organisms and suggest the entire water column was at least suboxic to support benthic life. The irregular laminae observed in all mudstones are interpreted as storm beds and counters the notion that the carbonate-siliciclastic transition is a product of storm wave base interaction. Rounded clasts in the carbonate rudstone (facies 6) reflect significant transport of those grains, likely from more proximal settings, and also indicate up-slope erosion. The geopetal cements are interpreted as indicating subaerial exposure following deposition. The exposure is likely the result of a glacioeustatic sea-level drop associated with the Gondwana glaciation during the late Hirnantian or at the Ordovician-Silurian boundary.Item Open Access Sedimentology, facies architecture and sequence stratigraphy of a Mississippian age, black mudstone succession -- the upper member of the Bakken Formation, North Dakota, U.S.A.(Colorado State University. Libraries, 2013) Borcovsky, Damien A., author; Egenhoff, Sven, advisor; Harry, Dennis, committee member; von Fischer, Joseph, committee member; Fishman, Neil, committee memberThe early Mississippian age, upper member of the Bakken Formation in the North Dakota portion of the Williston Basin consists of a succession of organic-rich, black siliciclastic mudstones deposited offshore on a low-gradient ramp or shelf. Based on ichnological and sedimentological characteristics twelve fine-grained facies are recognized within the succession and these are grouped into five reoccurring facies associations. Very fine-grained, massive to faintly laminated mudstone (FA1) records deposition in the deepest, calmest parts of the offshore environment, whereas well laminated mudstones (FA2a), well laminated clay clast-bearing mudstones (FA2b), burrow-mottled mudstone with shells (FA3), and interlaminated siltstone and mudstone (FA4) contain sedimentological evidence that argues for deposition in the shallower, less calm, and generally more proximal parts of the offshore environment. These proximal-offshore mudstones (FA2a, FA2b, FA3, and FA4) reflect (1) variation in overall bottom water oxygen levels from dysoxic to possibly as high as oxic, and (2) lateral variation in the input of silt and clay clasts along the basin margin. Ubiquitous Phycosiphon incertum fecal strings throughout the succession along with patches of small shells and centimeter-scale burrows, and rare agglutinated foraminifera indicate that the upper Bakken member was likely deposited primarily in dysoxic to suboxic basinal conditions, and not within a persistently stratified, anoxic environment. In all facies associations, storm event laminae deposited by bedload processes range from sparse to ubiquitous. Repeated stacking of facies associations, which reflect different offshore energy regimes define up to ten coarsening-upward parasequences mostly 0.15-0.60 m thick. These are bounded by flooding surfaces that can be correlated laterally for at least 300 km through the basin, delimiting individual parasequences. Distinct formation-scale facies changes indicate that the lower half of the succession, herein termed Interval 1, represents the distal expression of a transgressive systems tract and was characterized by high radiolaria productivity with minor silt input during higher order sea level lowstands. The upper half of the succession, herein termed Interval 2 represents the distal expression of the base of a highstand systems tract. In contrast to Interval 1, the Interval 2 mudstones are generally characterized by high clay content, low radiolaria productivity, and intermittent colonization of the sea floor by bivalves and millimeter to centimeter-scale burrowing organisms during higher order sea level lowstands. Core descriptions, radiolaria distribution patterns, x-ray diffraction data and comparisons to other shale plays in the United States of America suggest that mature mudstones in the Interval 1 part of the succession outside of the depocenter, and in isolated silt-rich sub-basins, might be sufficiently brittle and permeable to exploit for hydrocarbons utilizing horizontal drilling and hydraulic fracturing technologies.