Although multiple localized chemostratigraphic and strength studies have been completed on the organic-rich Barnett Shale in the Fort Worth basin (Montgomery et al., 2005; Pollastro et al., 2007; Jarvie et al., 2007; Rowe et al., 2008; Williams et al., 2016; Taylor, 2017; Alsleben, unpublished), basin-wide correlations have not been completed. Basin-wide correlation of chemostratigraphy and mechanical stratigraphy could enhance the understanding of regional variations in chemical composition and rock competence. Therefore, this study is going to test multiple hypotheses to identify regional trends and correlations within the Barnett Shale, based on variations in the formations chemical makeup and rock strength. The purpose is to start establishing a more comprehensive, basin-wide characterization of the mechanical stratigraphy and chemostratigraphic framework of the Barnett Shale in the Fort Worth Basin. Results will start to establish possible regional variations such as rock strength and help determine what controls those variations. Ultimately, the data compilation may provide a better understanding of the Barnett Shale and start to address the complex interactions between marine sediment flux, terrestrial sediment flux, and geochemistry throughout the basin at the time of deposition.
The geomechanical properties of Eagle Ford cores from the San Marcos Arch were measured by hardness tools to test that calcareous rocks are stiffer than the clay-rich shales. Results were quantified and graphed to reinforce the idea that the Maness shale could be more ductile than the superimposing Eagle Ford Shale.
Lithology and facies of the Lower Williams Fork in the Piceance Basin, Colorado were interpreted using spectral gamma ray logs on Petrel. Models were created using this correlated data to predict the facies in an area with no well data. Different modeling methods will be used, such as object modeling and sequence indication simulation to compare and search for the best fit. Published outcrop measurements were used to constrain subsurface geobody geometry. Models were also used to estimate reservoir rock potential in the Lower Williams Fork.
Silica oxides (SiO2) come in a variety of forms including quartz, opal, silica gel and phytoliths. This study will focus on the binding and debinding energetics of sodium benzoate, sodium butyrate and sodium acetate on these various silica oxides. The direct measurement and analysis of binding and debinding energies should provide valuable data and insights into the dynamics of organic molecules at the oxide-water interface. The study will focus on the systematic collection and analysis of experimental data that can be used to support the development, validation and refinement of computational models of interactions involving natural organic matter at the metal oxide-water interface, while facilitating the further development of experiment-driven understanding of binding-debinding dynamics of organic molecules onto mineral surfaces.
METASOMATIC FEATURES IN EUCRITES. R. L. Funderburg1, R. G. Mayne, N. G. Lunning2, and S. Sin-gletary3, 1Monnig Meteorite Collection, 2950 West Bowie Street, SWR 244, Texas Christian University, Fort Worth, TX 76109. (firstname.lastname@example.org), 2Department of Mineral Sciences, Smithsonian Institution, National Museum of Natural History, 10th and Constitution NW, Washington, DC 20560-0119. 3Robeson Community College, 5160 Fayetteville Road, Lumberton, NC 28360.
Introduction: The breakdown of pyroxene to silica and troilite was first identified as an alteration process in eucrites by Duke and Silver ; however, metasomatism was not iden-tified as a potential cause of these features until the 1990s  and has been increasingly identified in the last 10 years [3, 4, 5, 6, 7]. Many eucrite studies were conducted prior to this time and, while metasomatic features may have been identified, they were not attributed to this process.
Barrat et al.  proposed a three-stage alteration process to explain the products of metasomatic alteration found in eu-crites:
(1) Fe-enrichments along cracks in pyroxenes
(2) Fe-rich olivine deposits in cracks and troilite
(3) Al-depletion coincident with Fe-enrichment of pyroxene
While metasomatism within eucrites is now commonly identified within the literature, the mechanism for this altera-tion is not well understood. Possible mechanisms proposed in-volve hydrous fluid alteration  or sulfurization from a S-rich vapor [6, 7]. The addition of sulfur is required to produce troilite from the breakdown of pyroxene, which has been ob-served in several eucrites [3, 4, 5, 6, 7]. Zhang et al.  sug-gested that the sulfur may have been present in the form of a dry S-O-P vapor, formed by the volatilization of pre-existing S- and P-rich material as a result of impacts. Additional petro-logical studies are needed to test if metasomatism was consist-ently driven by S-O-P vapors or if some metasomatism lacks the P-component expected for impact derived vapor.
Metasomatism has been directly investigated for only a handful of eucrites. This study will investigate metasomatism in both Stannern and Main-Group-Nuevo-Laredo (MGNL) eucrites to investigate the com-position of the altering fluid/vapor and overarching processes that drive metasoma-tism on the eucrite parent body. Our preliminary work is fo-cused on the Stannern-trend eucrites Bouvante and LEW 88010, the main group eucrite Béréba, and the polymict eu-crite NWA 4834.
Methods: The samples from this study are on loan from the following: Béréba (USNM 5745-2, USNM 6003-2; Na-tional Meteorite Collection, Smithsonian Institution), Lewis Hills 88010 (LEW 88010) (LEW 88010,4; Meteorite Working Group), Bouvante and Northwest Africa 4834 (NWA 4834) (M1224.3, M1224.5, and M2049.2; Monnig Meteorite Collection). Petrographic analysis was conducted via optical micros-copy with an Olympus BX51 polarizing light microscope at the Oscar Monnig Meteorite Collection at Texas Christian University. Backscatter electron (BSE) maps and major ele-ment data for pyroxenes in Bouvante, LEW 88010, and NWA 4834 were measured by a JEOL JXA-8530F HyperProbe elec-tron microprobe analyzer (EMPA) at Fayetteville State Uni-versity’s Southeastern North Carolina Regional Microanalyti-cal and Imaging Consortium. Backscatter maps were gener-ated for each thin section and energy dispersive x-ray spec-trometry (EDS) point analyses were performed.
Results and Discussion: Of the four samples selected for this study so far, one is unbrecciated (LEW 88010), two are monomict (Béréba and Bouvante), and one is polymict (NWA 4834). These samples were selected as they were observed to contain possible metasomatic features during our petrographic survey, but have not been included in the current literature re-garding metasomatism. They include members of both the Stannern- and MGNL- trends (S: Bouvante and LEW 88010; MGNL: Béréba). All samples are either falls or were observed to show little to no terrestrial alteration. Mineralogically, they are typical eucrites, being dominated by pyroxene and plagio-clase, with lesser phases including troilite, chromite, ilmenite, Fe-rich olivine, and silica.
Preliminary results suggest that Fe-enrichment of pyrox-ene rims, along with an associated Al-depletion, is occurring due to metasomatism in the three samples examined using EMPA. Fe-rich olivine was observed in NWA 4834. Petrographic analysis identified the breakdown of pyroxene into troilite and silica in all four samples.
Future Work: Quantitative pyroxene and plagioclase data for all four samples will be collected prior to the conference. This will allow for further assessment of the Al-depletion along with Fe-enrichment in pyroxenes. We will also investigate the presence of phosphates in these samples to investigate the P-component that would be present in an impact derived vapor. We will assess if there are any differences in metasomatism between MGNL and Stannern-trend eucrites. A survey of previously identified residual eucrites for metasomatic features will also be conducted, so that all three geochemical groupings are represented, if possible.
The Raton Basin of Colorado and New Mexico is a Laramide foreland basin that has been important to coal geology since its first identification as a coal resource in 1821, and as a major Coal Bed Methane resource in the modern era. Raton Basin contains Cretaceous to Paleogene strata representative of the major transgression and subsequent regression of the Western Interior Seaway. The interaction between the distal and proximal lithosomes of strata within the Raton Basin is not fully understood. The coaly, fine-grained rocks of the lower and upper coal zones of the Upper Cretaceous to Paleogene Raton Formation are indicative of deposition in wet, distal lowlands, whereas the coarser grains of the barren series of the Raton Formation indicate that this unit was deposited in a highland setting proximal to the source. While the basin has been explored and produced for petroleum and coal in the past (specifically the Cretaceous Vermejo Formation and Raton Formation), vertical and lateral interaction, geometries, and potential communication between the coal deposits and surrounding fluvial deposits is not well-understood. This project has served as an investigation into the depositional model of the coal deposits and their surrounding fluvial deposits, specifically by: analyzing outcrops using architecture analysis, performing core descriptions and interpretations, conducting coal palynology, organic petrology, and chemical analysis. It has been proposed that the Upper Cretaceous to Paleogene strata of the Raton Basin were deposited within a Distributive Fluvial System (DFS), and that the coal-rich zone is the down-dip expression of this system. Initial results (vertical and lateral relation of facies in core and outcrop, organic petrology, and palynology) reveal that the extensive and laterally continuous coals formed in a woody low-lying fluvio-lacustrine depositional environment, and humid subtropical climate.
The Raton Basin of Colorado and New Mexico is a Laramide foreland basin that has been important to coal geology since its first identification as a coal resource in 1821, and as a major Coal Bed Methane resource in the modern era. Raton Basin contains Cretaceous to Paleogene strata representative of the major transgression and subsequent regression of the Western Interior Seaway. The interaction between the distal and proximal lithosomes of strata within the Raton Basin is not fully understood. The coaly, fine-grained rocks of the lower and upper coal zones of the Upper Cretaceous to Paleogene Raton Formation are indicative of deposition in wet, distal lowlands, whereas the coarser grains of the barren series of the Raton Formation indicate that this unit was deposited in a highland setting proximal to the source. While the basin has been explored and produced for petroleum and coal in the past (specifically the Cretaceous Vermejo Formation and Raton Formation), vertical and lateral interaction, geometries, and potential communication between the coal deposits and surrounding fluvial deposits is not well-understood. It has been proposed that the Upper Cretaceous to Paleogene strata of the Raton Basin were deposited within a Distributive Fluvial System (DFS), and that the coal-rich zone is the down-dip expression of this system. This hypothesis was tested by integrating results from well log correlations, measured sections, architecture analysis of outcrops from drone photogrammetry, core descriptions, and coal palynology and microscopy. Initial results reveal the presence of three distinct, repeating lithosomes (valley-fill sandstones, mixed terminal splays, and very extensive and laterally continuous coals) that are identifiable and correlatable in well logs, are cyclically represented, and suggest basin-scale swings in depositional environment consistent with shifting components within a basin-wide DFS system, consistent with the DFS hypothesis.
The ~1.2 billion-year-old-Barby Formation is located in SW Namibia and has been argued to represent a continental volcanic arc. Previous studies on these rocks primarily relied on mobile-element data, which can be altered by secondary processes and therefore is unreliable for constraining petrologic processes. In an effort to establish the Barby Formation's petrotectonic history, 20 samples were analyzed using XRF and ICP-MS to determine whole-rock major and trace element concentrations. These data were used to answer two questions: (1) Do the samples represent one unique magma series that came from a single source? (2) If the Barby Formation is indeed a volcanic arc, did it form from normal, flat-slab, or oblique subduction? These questions were answered using a combination of geostatisical analyses (distribution, cluster, and outlier analyses), trace-element tectonic discrimination diagrams, and geospatial analyses (see other poster by Lehman et al.). This study supports previous interpretations that the Barby Formation formed in a continental arc setting, with rock samples displaying steeply dipping, light-rare-earth-element enriched patterns, negative Nb/Ta anomalies, and calc-alkaline andesitic to shoshonitic compositions. Major and trace element data indicate at least two magma series from two distinct mantle sources. These two groups are controlled by enrichment differences and variations in the high-field-strength element ratios. The presence of shoshonitic rocks is consistent with flat-slab or oblique subduction.
The ~1.2 billion-year-old-Barby Formation located in SW Namibia has been argued to represent a continental volcanic arc. Recent research by our group (see other poster by Lehman et al.) has supported these arguments with data exhibiting steeply dipping, light-rare-earth-element enriched patterns, negative Nb/Ta anomalies, and calc-alkaline andesitic to shoshonitic compositions. The shoshonitic rocks are particularly interesting as these compositions often form in unusual arc settings (i.e., flat-slab subduction, oblique subduction, ridge subduction). Pearce et al. (2005) showed that the relative plate depth, and in turn, subduction angle and orientation can be interpreted by mapping diagnostic trace element ratios. The spatial distribution of the geochemical ratios could potentially also differentiate between shoshonitic volcanic rocks formed as a result of unusual plate geometries as opposed to a slab tear. If the map displays a tight cluster of shoshonitic composition rocks, the samples more likely formed above a slab tear, while a dispersed arrangement would be more suggestive of either a flat-slab or oblique subduction origin. ArcGis Pro was used to map and analyze XRF and ICP-MS data from 20 samples of the Barby Formation. The samples are from lava flows or sills and range from calc-alkaline to shoshonitic in composition. Both spatial tools and statistical analysis tools were used in an effort to explore potential geospatial relationships of key trace element ratios and previously established geochemical clusters. These results were then employed to attempt to recreate the subduction conditions that formed this volcanic arc.
The depositional model of the Festningen Member of the Barremian Helvetiafjellet Formation is that fluvial to inner deltaic-plain conditions were established as deltas that built southeastward into the Barents Sea basin from an unknown source northwest of present-day Svalbard. Currently, models of Artic drainage provinces are nascent to non-existent. Here, evidence for a large artic drainage basin into the Cretaceous Barents Sea is suggested by using established scaling relationships and the fulcrum method in the Festningen Sandstone.
Data from several locations in Svalbard: Konusdalen, Revneset, Criocerasaksla, and Hanaskogdalen. The Festningen Member sandstone sections were all initially photographed by drone in order to determine channel body dimensions and architecture in the sandstone as well as to record data for 3D photogrammetric construction of virtual outcrop models. Paleohydraulic estimates based on the fulcrum method use bankfull channel dimensions, specifically the height and width, and the D16, D50, D84, and D90 grainsizes to develop basin-process models and infer past catchment constraints. Festningen Member sandstone sections were logged and found to represent braided fluvial systems with mid-channel bars up to 3 m thick and channel-fills up to 4 m thick. Representative bedload samples were taken from approximately 10 cm above the base of channel scours for analysis and model input. The coarse grainsize and large clasts, frequently 3-4 cm and up to 15 cm in diameter, in the Festningen Member sandstone samples show that this was a large river capable of moving a coarse bedload. Scaling relationships equivalent to 4 m channels and coarse grained D-values is on the order of the modern braided Missouri River, on the South Dakota/Nebraska border.
The Bjarmeland Platform and Fingerdjupet Subbasin in the western Barents Sea have a potential petroleum play in the Lower Cretaceous strata, which are, in part, considered to have been fed by the same Festningen fluvial system that is represented in cliff sections on Svalbard. Seismic profiles show clinoforms that may suggest deltaic facies, but remains unknown due to lack of well data.
Seismic data shows that the Cretaceous Festningen fluvial system was able to deliver enough sediments onto the Bjarmeland Platform area to build clinoforms. The size of the source area sufficient to produce a trunk river on this scale remains unconstrained, but an area of at least 100,000 km2 is necessary to produce the river found in the rock record, if the Fulcrum method is applied. Existing Arctic tectonic reconstructions do not consistently show a land area of sufficient size to accommodate this magnitude of drainage area, but results from this study may provide further input to the discussion on timing and land-mass configuration in the present day arctic during the Early Cretaceous.
The 1.2 Ga volcanic arc rocks in the Barby Formation are well exposed in desert terrain in SW Namibia - this formation records the establishment of a major continental margin arc following earlier accretionary events. Recent field work has shown that large portions of the formation consist of pyroclastic fall deposits erupted from small volcanoes (fissures and scoria or spatter cones) in a region with poor drainage and abundant lakes.
Detailed mapping of a well-exposed section of the Barby Formation provides a cross-sectional view of a succession of pyroclastic fall units intercalated with planar bedded lacustrine sediments. Massively bedded units up to ~80 m thick show abundant bombs up to 60 cm across in a matrix of fluidal to angular lapilli, indicating deposition close to source vents undergoing primarily Strombolian-type eruptions. Hypabyssal dikes and sills are common, often cutting through the massively bedded pyroclastic units.
Also present are pyroclastic deposits that intrude lacustrine sedimentary packages at 12 locations spread out over a horizontal distance of ~600 m and a vertical stratigraphic sequence of ~300 m. These deposits contain similar bombs and lapilli as the pyroclastic fall deposits, but show clear fluidal intrusive relations with adjacent sedimentary units. In most cases, zones of peperite are formed in between the pyroclastic intrusions and the lacustrine sediments, consisting of fluidal bodies of vesicular basaltic andesite mingled with fine-grained sediment with preserved lamination. We infer that jets of intrusive pyroclastic material were blasted laterally into weak, unlithified lake sediments from one or more vent conduits feeding explosive eruptions at the surface; these jets are likely to have been forced out by collapse of the conduit inward. Fluidization of the sediment would have occurred as pore water was converted to steam, which would have facilitated lateral motion of the pyroclastic jets.
Landsat-8 data was used to test the effectiveness of using spectral analysis and remote sensing in the differentiation of lithological units and mapping geology in Namibia. The study area is located in SW Namibia, in an arid region with little vegetation, making it an ideal place for remote sensing analysis. Different color composites and band ratios were compared to find the image providing the most geologic information and highest contrast between units. A false color composite (6,3,2 in red-green-blue) was first created to to show differences in bare earth, and from there, various band ratio combinations were created. Geologic maps were used to verify the results and select the best band combination. The best color composite image was created using band ratios from (7/6, 6/5, 4/2), and allowed identification of lithological units and vegetation. The results show that it is possible to draw valid lithological conclusions from spectral patterns, and that high quality imagery can be used to update existing geologic maps or used for exploration.
SRS Abstract Drainage Area Climate Classification
For my SRS project I will be determining the climate(s) within a given polygon. The Polygon size and shape will be determined from a specified drainage area for a given stream. I will be using over 400 stream data points with a series of drainage area shape files given to me by Nicole Wilson. I will base the climate on the gauge site location within the drainage area. The koppen climate classification scheme will then be used to specify each drainage area.
Unconventional shale plays have been a significant source of natural gas, gas condensates, and crude oil through much of North America. The Eagle Ford Shale in south Texas has been a prolific unconventional play since the mid-2000’s. It was deposited in the Gulf Coast basin along the southern rim of Texas. This play covers a vast area that stretches approximately 7 million acres (2.8 hectares) and extends from the College Station to the USA-Mexico Border near Del Rio. The majority of the Eagle Ford has been thoroughly studied and analyzed, however, there is much to learn about the basal member, the Maness Shale.
The Maness Shale was deposited 97 million years ago; it is the basal member of the Eagle Ford Group and lies directly above the Buda Limestone. The formation does not occur continuously throughout the entire Eagle Ford deposition and varies in thickness. Whereas the lateral extent still remains unknown, it has previously been mapped across the San Marcos Arch. The geophysical and geochemical properties of this member create drilling stability issues if encountered while drilling horizontal Eagle Ford wells. To further understand its geomechanical properties, two hand-held devices will be used on cores taken near the San Marcos Arch that contain the Maness Shale to determine rock strength variations of the Eagle Ford section. The Equotip Bambino is a micro-rebound hammer that provides hardness data values that can be used to estimate unconfined compressive strength. The dimpler is a micro-indentation device that infers rock strength by generating a “dimple” created by the tool and then measuring the depth and diameter of the dimple. These measurements are then correlated on graphs against the unconfined compressive strength for the regional Eagle Ford. The Maness has a neutron density range of 20-30%, indicating a high clay content. The x-ray diffraction (XRD) will be used to determine the content of the clay minerals. Geophysical well logs have been collected and correlated across the San Marcos Arch region; the initial maps identified the thickest Maness interval within the Karnes trough.
The sequence stratigraphy of Middle to Upper Pennsylvanian strata in the Appalachian Basin is complex, partly owing to the icehouse co-response to climate and sea level change during the late Paleozoic. The Breathitt Group resembles a traditional marine-to-terrestrial sequence stratigraphic model. The overlying Conemaugh Group also exhibits sequences, but they are more fluvial-dominated. Sequence stratigraphy largely presumes sea-level drive for sequences and accommodation. We present a model that is driven by both sea level and climate. We hypothesize that once the land surface is built up high enough above the water table, it is not required that sea level drop to induce valley incision, and in fact there is no evidence for a shelf slope break that would promote incision. Instead, we offer that climate change may be the main driver of valley incision.
This model is tested using strata in the Breathitt and Conemaugh Groups in the Northern and Central Appalachian Basin. Measured sections along a basin cross section in outcrop and 3D models built from UAV photographs help reveal this past environment to address the potential of climate change as a sequence driver.
The Breathitt to Conemaugh Group shift records a composite of sequences that are a progradational basin-fill and define a switch from a mixed marine and fluvial to fluvial fill. The Conemaugh sequences record upward shifts from a low-accommodation, valley-incised tributive to a high-accommodation, un-incised distributive systems tract. As a marine transgression tops the low-accommodation valleys below, it lays a basal peat which floods the tributive system. Next, the rivers in the distributive fluvial system prograde and push out the shore, as well as build a slope above sea level. This aggradation creates an elevated coastal prism. Continued progradation creates the elevation needed for valley incision, but this progradation need not cause incision, even if sea level falls. A climate change will eventually spur water table reduction owing to a locally drier climate, or an upstream water-sediment ratio change. Valley incision begins at that time, and possibly with no change in sea level. In this model, regression with or without sea level drop sets up the conditions needed for valley incision, but does not cause incision itself. Incision waits for adequate climate change to generate buffer valleys. The valleys record regression but are climate driven and do not have to define sea-level change.
The purpose of this study is to construe the geologic history and development of the Sand Wash Basin and investigate possible hydrocarbon prospects in the Sand Wash Basin, Colorado. Regional sequence stratigraphic correlation and interpretation will be based on 95 raster log data in Moffat County in northwestern Colorado with a focus on upper Cretaceous aged sediment. All well log correlations will be based on Gamma Ray, Spontaneous Potential and Resistivity logs using type logs defined in southern Wyoming. Through examination and comparison of lithology, log signature patterns, and fancies interpretation, I will be able to construct regional cross-sections to understand the sequence stratigraphy, and development of the Sand Wash Basin. Facies and isopach maps of potential reservoir units will help identify and define potential hydrocarbon plays in the Sand Wash Basin. All results can be applied to the Great Green River Basin in Wyoming and Colorado as well as other Laramide basins in the Rocky Mountain area.
Public awareness of human rights violations in cobalt-rich mines of the Democratic Republic of Congo have American cobalt consumers scrambling for reliable suppliers to meet rising demand, with uncertainties about futures in cobalt's supply chain. Global cobalt production supply forecast falls short of global demand forecast for the next ten years, even with the completions of major planned mined projects. The exponential increase in demand for cobalt results from its utility in personal electronics batteries, electric vehicle batteries, and jet engine construction. Chemical extracting operations whose sole purposes are to extract cobalt are not profitable in the status quo, leaving a window of opportunity for reclaimed cobalt to take hold in the market. This project studies consumer patterns to determine "urban mine" qualities in Texas. The resulting analysis exists to be cross-applied to other states to determine target regions best suited for cobalt reclamation strategies in hopes of securing America's geopolitical mineral stability.
Due to the logistical challenges and the dynamic nature of fluvial systems, studying modern point bar deposits over formative time periods is difficult. Seasonal and annual changes in precipitation can greatly influence the rate at which deposition is recorded. The lack of accurate sediment-package dating makes it difficult to compare sedimentation rates to actual chronostratigraphic events such as floods. This study combines photogrammetry, mapped surface migration, a survey of sediment elevation change, a trench, and water discharge rates to develop a more complete understanding of how a point bar forms on an annual scale. The Powder River, Montana, USA, which has little influence from engineering, offers a unique opportunity to study a seasonally exposed point bar and how its internal architecture and surface features form through time.
The study area is along the Powder River between Moorhead, Montana, USA, and Broadus, Montana, USA. The Powder River is a northward flowing, meandering river that is sourced from the Bighorn Mountains in northeast Wyoming, USA and is a tributary to the Yellowstone River. Point bar PR141A, the focus of this study, is the result of the neck cut-off of point bar PR141 during a 50 year flood in 1978. The sediment elevation survey is conducted annually, with a few exceptions, at centimeter scale to determine sediment elevation change and the building and erosion of the point bar. The survey is applied to the architectural-element analysis of the sediment packages within the point bar to compare time with sediment deposition.
This study reconstructs the growth of point bar PR141A, its discrete accretionary architecture at the scale of years, and determines the inter-relationship between annual flooding events and bar accretion. The sediment survey timeline shows that on average the river builds one accretionary body per yearly flood cycle. On occasion, the river builds multiple bodies during the year or can take several years to build one accretion set. The change in the accretion set building period is attributed to changes in river flow. The continual change of deposit direction, grain size distribution, erosion, and reshaping of the bar surface between accretion events leads to fragmentation of the point bar body, vastly different from the textbook model of a point bar. The detailed study of how a modern point bar forms lends insight into the fragmentation of fluvial hydrocarbon reservoir bodies.
The Eagle Ford Shale (EFS) was deposited on the South Texas Shelf in the Late Cretaceous, during a time of widespread marine transgression. With industry interest in the EFS, an understanding of the geology and depositional environment of these rocks is imperative to maximize well results. For the study, a section of the EFS was measured and described in detail in Heath Canyon, Brewster County, Texas. Lithostratigraphy, biostratigraphy, and mechanical stratigraphy were determined via outcrop and elemental composition was determined from sample collection and lab analysis. Data suggests the EFS was deposited in a potentially anoxic environment below storm-wave base on the South Texas Shelf.
Quantifying source-to-sink sediment flux for stratigraphic systems is critical for accurate basin models, but all available methods are hampered by low precision and most require data not readily attained by common subsurface studies. The Fulcrum approach uses the variables of channel bankfull thickness and grain size to calculate sediment bankfull discharge and converts this to an annual sediment volume. The Fulcrum approach uses commonly collected data but similarly yields only approximate flux estimates. In order to calculate a more precise source-to-sink estimate for long basin durations, the amount of time the fluvial systems runs at bankfull flow and the annual proportion of sediment discharged during this bankfull flow must also be determined. By categorizing fluvial systems by attributes such as drainage area and paleoclimate at the time of discharge, a more specified and accurate bankfull flow duration and total bankfull sediment discharge is estimated. We constructed a database that stores and categorizes these data and a user interface (RAFTER: River Analogue and Fulcrum Transport Estimates Repository) to query and display this data. Daily stream gauge data spanning decades is used in conjunction with measured bankfull values from literature to populate the datasets for the database and derive stream specific data attributes. This bankfull flux searchable database evaluates stream gauge data for modern fluvial systems according to classes such as climate setting and is also a useful tool for identifying analog stream data scaled to drainage basin and channel size. It evaluates designated parameters of days within a year that the river runs at bankfull flow, as well as the yearly proportion of sediment discharged over bankfull duration. The database can thus yield a more accurate value for duration at bankfull flow and sediment discharge at bankfull from modern rivers that can be used as an analog for stratigraphic rivers with interpreted climate and size parameters. Results show a key breakdown in bankfull duration, with arid and tropical rivers on the order of a fraction of a day per year, boreal climates tending to be an order of magnitude longer, and temperate climates still longer. Categorizing stratigraphic rivers by known climate and other parameters can lower the total error in sediment flux from paleohydrology by a geometric factor.
The Barby Formation makes up part of the Konkiep Terrane, which is a major Mesoproterozoic arc complex along the Kalahari craton margin in southwest Namibia. Previous mapping indicates that the Barby Formation contains a laterally and vertically complex series of basaltic to rhyolitic lavas, rhyolitic ignimbrites, and associated hypabyssal intrusions. Our new work shows that significant basaltic to andesitic pyroclastic successions are also present within the unit and record a wide variation in eruption styles.
Detailed mapping reveals the presence of Hawaiian, Strombolian and phreatomagmatic pyroclastic deposits forming successions up to X m thick emplaced close to source vents and intercalated with fine-grained lacustrine strata in an area ~20 km2. The most abundant deposits consist of basaltic to andesitic spatter accumulations formed from vigorous lava fountains during Hawaiian-style eruptions. These sequences show random vertical transitions on the scale of a few meters from moderately agglutinated to densely welded spatter, which reflect variations in pyroclast accumulation rates. Individual spatter pieces are up to x cm long. The densely welded spatter forms lava-like units, but we see no evidence of clastogenic lava flows. Sequences of basaltic lapillistone with dispersed ribbon and fusiform bombs up to 50 cm across record Strombolian eruptions during episodes of lower magma flux without involvement of external water. The spatter accumulations typically grade upward into phreatomagmatic deposits containing minor amounts of spatter and cauliflower bombs mixed with poorly vesicular lapilli tuff, in which particle shapes are controlled mostly by fracture surfaces rather than broken bubble walls; up to 30% lacustrine sediment is intermixed with juvenile lapilli and ash in these deposits. We infer that changes in eruptive style in this part of the arc sequence were controlled at least partly by variations in magma ascent rates at shallow depths, as documented in numerous other volcanic provinces. Transitions from Hawaiian to phreatomagmatic eruptions may at least partly reflect a decrease in magma flux in the presence of external water, lowering the magma-to-water mass ratio so that hydrovolcanic explosions became possible.
Northwestern South America is highly deformed due to the transpressive boundary with complex interactions among the Caribbean plate, the South American plate, the Nazca plate and the Panama arc. Previous studies suggest that the Cenozoic uplifting of the Mérida Andes and Eastern Cordillera of Colombia affected sediment dispersal patterns in the region, shifting from a Paleocene foreland basin configuration with an axial major fluvial system, to the modern configuration of isolated basins with distinctive sediment dispersal patterns. Well-exposed Cretaceous to Pliocene strata in the Táchira saddle between the Easter Cordillera and Merida Andes provide a unique opportunity to test proposed sediment dispersal patterns in the region. U-Pb detrital zircon geochronology and supplementary XRD heavy mineral identification were used together to document provenance of Cretaceous to Pliocene clastic rocks collected from the area of La Alquitrana. Results from the U-Pb detrital zircon geochronology show that there are six age groups recorded in this samples. Two groups related with Precambrian Guyana shield Terranes and Putumayo basement in the Eastern Cordillera, and four groups related to different magmatic episodes during the Andean Orogenic process. Three major paleogeography changes were also recorded in these detrital signatures, including a transition between the Cretaceous passive margin and the Paleocene foreland basin, the initial uplifting of the Eastern Cordillera with the isolation the Llanos Basin and Táchira Saddle from the Central Cordillera and the Magdalena Valley in the Early Oligocene, and the uplifting of the Mérida Andes by the Early Miocene. The outcomes of this study emphasize the importance of the Mérida Andes and Eastern Cordillera Uplift in controlling the evolution of the sediment dispersal patterns in northern South America and represent a contribution in the understanding of the paleogeographic evolution in the region.
Fluvio-lacustrine systems are prone to experiencing significant flood events separated by longer low energy periods. During low flow, sediment is stored upstream of the lake as mid-channel and side-attached bars. During high-discharge events, water level rises above the topographically low delta front levees, the turbulent jet of the river is positioned upstream of the levee terminus where levees are less confining, and the previously stored sediment is flushed from the channel into the lake basin laterally as sheets. This process forms a laterally extensive, well sorted wedge shaped deposit of fine grained sand called a blowout wing (after Tomanka, 2013). These wings are documented in the ancient within the Kayenta Formation, UT, where the sand wings demonstrated a significant increase in connectivity between statistically clustered fluvio-lacustrine channel belts. In this research, we document two examples of blowout wings forming in the modern. The first example is a lake sourced by a mud dominated river (Denton Creek, Lake Grapevine, TX), and the second is a lake sourced by a sandy, bedload dominated river (Red River, Lake Texoma, TX). Wings are composed of fine to medium grained, well sorted, and clean sand. The deposits are thin and laterally continuous, with measured thicknesses of 5-10 cm that thin away from channel axis. Wings have an aerial extent up several hundred meters, scaling to 4-6 times the channel width. The Red River at Lake Texoma has a channel width of 125m and deposits wings with an aerial extent of 250-350m long along the levee of the delta channel and 300-500m laterally. As the Red River has prograded into the basin, 5-6 individual blowout wings form a wing complex 1500m long and 500-600m laterally from the channel. Denton Creek at Lake Grapevine has a channel width of 25m and deposits wings on the order of 50-125m along the levee of the delta channel and 60-150m laterally. Three wings at Lake Grapevine form a wing complex 300m long and 100-150m laterally. The amalgamation and statistical clustering of fluvio-deltaic channel belts is increased by the presence of blowout wings, resulting in higher total reservoir size and connectivity. Blowout wings should be, and are, found in modern systems and subsequently the rock record recording fluvio-lacustrine environments of deposition.
Thin sand sheets presumed to be terminal splay bodies have potential to serve as hydrocarbon reservoirs. The few studies of terminal splays managed from arid systems has provided insight, but ground study of the humid equivalent is lacking. Deposited in the distal zone of a distributary fluvial system (DFS), the splay bodies are formed as rivers terminate from loss of slope into unconfined dispersive flow and deposit bed load as splays and advect mud to more distal floodplains. The splay sheets and floodplain together provide potential for both reservoir and seal. We examined terminal splay deposits in a modern humid terminal splay system, Andean foreland of northern Argentina, and in ancient foreland deposits, Paleocene Raton Formation of the Colorado Raton Basin. I am going to compare the two locations in terms of grain-size, sedimentary structures, geometry, and scale and see how they relate. I hypothesize that the two are going to have similar grain sizes, and that the sedimentary structures and geometries will also be analogous but expect them to be scaled down in the Raton Basin.
The modern splay in Argentina is nearly 1.3 km wide and 1.9 km long and was deposited during a single large flood in 2012. Cross sections generated by hand augers show a maximum thickness of 0.8 m, an average of 0.5 m, and a consistently very fine-grained to lower medium-grained sand texture throughout. Total sand deposited in the flood event is ~ 1.2 million cubic meters (~2.0 million cubic meter maximum), and accumulates over earlier splay deposits separated by weakly developed soils that are locally removed by splay incision. Subsequent dissection of the splay permits examination of sedimentary structures, which are dominantly climbing ripples, planar laminations, and cross sets, but climbing antidunes are locally found near the splay apex. Ancient terminal splays of the Raton Formation are made of thinner sand sheets (~0.25 m) and tend to have thicker muddy floodplain deposits between. Grain-size distribution, sheet geometry, and sedimentary structures however are consistent between the modern and ancient examples. Both the Argentina and Raton examples reflect the distal end of a humid Distributive Fluvial System, however, the Raton system appears to have been of smaller scale. This is consistent with the comparatively smaller scale of the Raton vs. Andean tectonic system.
The Late Paleozoic Ouachita fold-and-thrust belt extends from the southern terminus of the Appalachian thrust belt in eastern Mississippi up through central Arkansas, southeastern Oklahoma, and Texas terminating in northeastern Mexico. A series of Carboniferous foreland basins were formed sequentially to the thrust front. The interaction between the Laurentian craton and the Appalachian-Ouachita orogenic belts controlled sedimentation in the southern midcontinent region throughout the Paleozoic. In contrast to the Appalachian orogenic belt to the east, the Ouachita orogenic belt and associated sediments remain poorly documented and less constrained.
In this study, seven Ordovician to Mississippian aged clastic units from the Ouachita Mountain in central Arkansas were sampled and tested using U-Pb detrital zircon geochronology. Three major age peaks are prominent, including the Grenville Province (~0.95-1.2 Ga), the Granite-Rhyolite Province (~1.3-1.5 Ga), and the Superior Province (>~2.5 Ga) in Ordovician to Silurian aged rocks. A change in this signature becomes clear at the beginning of the Carboniferous from Early Mississippian Stanley Group samples showing the additional Paleozoic age peak (~490-520 Ma) potentially derived from the Appalachian orogenic belt to the east, and/or from peri-Gondwanan terranes accreted to Laurentia just before the collision with Gondwana. This stratigraphic variation of detrital zircon age signature suggests that the transition from a passive to an active margin in the Ouachita trough started, at the latest, in early Mississippian times. Results of this study is the first systematic study of the U-Pb detrital zircon signature of the Ouachita orogenic belt and have important implications in sediment dispersal, provenance interpretations, and paleogeography reconstructions in North America, especially in the southern mid-continent and surrounding areas.