Forest City Basin Research Articles

The Devonian-Carboniferous boundary in the United States

The Devonian-Carboniferous boundary is documented in marine strata from the Appalachian Basin, Michigan Basin, Illinois Basin, Forest City Basin, Williston Basin, Tobosa Basin, southern continental margin, western platform, and several sub-basins of the Antler Foreland in the USA based on conodonts, brachiopods, miospores, carbon isotope data, and magnetic susceptibility data. The boundary is narrowly constrained and conformable in the Illinois Basin and Oklahoma; less well constrained in the Appalachian Basin, Antler Foreland, western platform, and the Alberta Platform, and often developed on an unconformity.

Detrital zircons and sediment dispersal in the eastern Midcontinent of North America

Abstract Results of detrital-zircon analyses (U-Pb ages and initial Hf values, εHft) of Mississippian–Pennsylvanian sandstones in the Michigan, Illinois, and Forest City basins are remarkably similar to data for coeval sandstones in the Appalachian basin, indicating dispersal of sediment from the Appalachian orogen through the Appalachian basin to the eastern Midcontinent during the late Paleozoic. The similarities of results include matches of the two most prominent age groups (1300–950 Ma and 490–350 Ma), as well as matches of the less abundant age groups. Comparisons of the data are from observations of probability density plots and multidimensional scaling of U-Pb age data and of εHft values. Despite the dominance of an Appalachian signature in all samples, some samples contain grains with ages that suggest intermittent additional sources. Four samples (three ranging in depositional age from Morrowan to Atokan–Desmoinesian in the Illinois basin, and one of Desmoinesian age in the Forest City basin), in addition to typical Appalachian age distributions, have prominent age modes between 768 and 525 Ma, corresponding in age to Pan-African/Brasiliano rocks in Gondwanan accreted terranes in the Appalachian orogen, suggesting intermittent dispersal from the Moretown terrane of the northern Appalachians. Sandstones in the Appalachian basin and those in the Midcontinent basins have very few grains with ages that correspond to the Alleghanian orogeny in the Appalachian orogen. Nevertheless, three sandstones each in the Illinois basin and Forest City basin with depositional ages of 312–308 Ma have a few zircon grains in the age range of 321 ± 5 to 307 ± 4 Ma. The nearly identical crystallization and depositional ages suggest reworking at the depositional sites of air-fall volcanic ash from the Alleghanian orogen, rather than fluvial transport from the orogen. The basal Pennsylvanian sandstones lap onto a regional unconformity around the northern rims of the Illinois and Forest City basins, suggesting sources for recycled grains. Along the northern edge of the Illinois basin, Ordovician sandstones beneath the unconformity may have contributed minor concentrations of Superior-age zircons in the basal Pennsylvanian sandstones. Basal Pennsylvanian sandstones in the Forest City basin lap onto Mississippian strata, suggesting possible recycling of zircons from eroded Mississippian sandstones.

Generation of Pseudo-synthetic Seismograms from Gamma-Ray Well Logs of Highly Radioactive Formations

The conventional synthetic seismogram is created with a sonic and a density log; however, the sonic log can be replaced with the resistivity, neutron, gamma-ray or spontaneous potential log to produce a pseudo-sonic (PS) log. More recent techniques involve combining an SP log and a GR log to produce a PS log. In the past, a drawback in using GR logs for the PS is the presence of highly radioactive and often organic-rich layers possessing abnormally high GR readings. To improve the pseudo-sonic log produced from the gamma-ray log, a technique was developed to statistically treat the outliers from the wells in the Hugoton Embayment that encountered predominantly shale, sandstone, limestone, and dolomite and whose logged sections included both normal and abnormally high GR readings. To demonstrate a wider-range application of our method, the procedure was applied to wells from the Hugoton Embayment, Central Kansas Uplift, Sedgwick Basin, Salina Basin, Forest City Basin and Nemaha Uplift. The correlation coefficients between the PS and the conventional sonic for the six basins were 0.75, 0.92, 0.86, 0.91, 0.77, and 0.70, respectively. Also, the match between the resulting conventional synthetic seismogram and the pseudo-synthetic seismogram from a blind test well for each area was quite good. Provided the outliers have been properly treated, the GR log is a viable tool for creating pseudo-sonic logs and pseudo-synthetic seismograms for exploration in oil and gas basins where there are few wells with sonic logs or where sonic log quality is poor.

Lead and sulfur isotope composition of trace occurrences of Mississippi Valley-type mineralization in the U.S. midcontinent

Mississippi Valley-type (MVT) Zn-Pb mineralization in the U.S. mid-continent has formed in numerous widely dispersed trace occurrences and in a few large ore deposits that have been mined. Based on similarly high fluid inclusion salinities and high homogenization temperatures relative to inferred burial depth, the trace MVT occurrences and MVT ore deposits may be genetically related by having precipitated from the same regional groundwater flow system mobilized by Pennsylvanian-Permian tectonism. The purpose of the present study was to test the robustness of this inferred genetic relationship by characterizing the Pb and S isotope composition of trace MVT occurrences in light of the much more thoroughly studied MVT ore deposits.Lead and sulfur isotope compositions have been obtained for trace MVT occurrences from three broad regions of the U.S. mid-continent: the Forest City basin (FCB), the Illinois basin (ILB), and the Greater Upper Mississippi Valley (GUMV) region. Lead isotope compositions of trace MVT occurrences from each of these three areas define discrete linear trends that are similarly oriented but not strictly collinear with one another or with the Pb isotope trends of MVT ore deposits, suggesting that trace MVT occurrences in each of these three regions derived their Pb from separate pairs of end-member Pb sources. An exception is the GUMV trace MVT occurrences and the Upper Mississippi (UMV) district ores, which appear to have collinear Pb isotope trends and thus may be the most closely related genetically with respect to sources of Pb. All of the trace MVT occurrences have radiogenic Pb suggesting derivation from Precambrian igneous basement rocks and not from the formations that host trace MVT mineralization. Trace MVT occurrences tend to have less radiogenic Pb than the MVT ore deposits, although trace MVT occurrences from the GUMV region are the most heterogeneous and can have Pb that is as radiogenic as the MVT ore deposits. Regionally, Pb isotope compositions of trace MVT occurrences tend to become less radiogenic southwestward and southward, but do not correlate with host rock age, and by proxy, distance from the Precambrian basement.The sulfur isotope compositions of sphalerite and galena from the trace MVT occurrences are light compared to the MVT ore deposits and likely reflect incomplete reduction of marine sulfate reservoirs or derivation from organic matter. The Pb and S isotope compositions of the trace MVT occurrences do not correlate well, suggesting that Pb and S were not transported together in the same fluid.

Hydrology of the Forest City basin, Mid-Continent, USA: implications for CO2 sequestration in the St. Peter Sandstone

The central United States contain numerous coal-burning electric power plants that emit large amounts of CO2 for which a nearby suitable disposal site would be desirable. The results of a reconnaissance study reported here indicate that the St. Peter Sandstone in the Forest City basin has potential large-scale CO2 sequestration capacity, despite the basin’s overall relatively shallow depth. A three-dimensional stratigraphic model of the basin constructed from published well logs reveals that about 59 % of the St. Peter in the basin lies below a depth of 750 m, where CO2 would exist in a supercritical state for increased storage efficiency. Based on a porosity of 15 % and a storage efficiency factor of 5.4 %, the St. Peter in the basin could potentially sequester upto ~830 M tonnes of CO2, equating to upto 23,500 tonnes of CO2 per km2. A three-dimensional hydrologic model coupling groundwater flow, heat transport, and salinity transport provided insights into how CO2 might be transported in the basin. The results show a consistent pattern of predominantly southwestward groundwater flow in the northern part of the basin and predominantly eastward flow in the southern part of the basin. Groundwater average linear velocities are known with much less confidence, but in the St. Peter are mostly under 10 m/year and lack a strong vertical component. Mineralogical analysis shows the St. Peter to be composed almost entirely of quartz, suggesting that the St. Peter would be resistant to dissolution by CO2-enriched fluids and accompanying increases in porosity and permeability.

Biogeochemistry of the Forest City Basin coalbed methane play

Abstract Hydrogeochemical and microbial analyses of co-produced formation waters and gas in the Forest City Basin were coupled to determine the origin of methane in shallow coal seams and make comparisons to commercial shale and coal gas plays in the adjacent Illinois, Michigan and Cherokee basins. Forest City Basin coals contain dilute meteoric waters (Cl−

Palynological Correlation of Atokan and Lower Desmoinesian (Pennsylvanian) Strata Between the Illinois Basin and the Forest City Basin in Eastern Kansas

Palynological correlation is made between Atokan and lower Desmoinesian strata in the Illinois basin and the Forest City basin in eastern Kansas. Spore data from previous studies of coals in the Illinois basin and other coal basins are compared with data from spore assemblages in coal and carbonaceous shale bands in a core drilled in Leavenworth County, Kansas. Correlations are based on first and/or last occurrences of 31 species common to the Illinois basin and eastern Kansas and on significant increases or decreases in abundance of several of those taxa. The oldest coal, which is 26 ft (8 m) above the top of the Mississippian, is early Atokan (early Westphalian B) in age and is approximately equivalent to the Bell coal bed in the Illinois basin. The Riverton coal bed at the top of the studied interval in Kansas is early Desmoinesian (early Westphalian D) and correlates with about the Lewisport coal bed in the Illinois basin. Three coal beds near the base of the Pennsylvanian in three cores drilled in Cherokee County, Kansas, which were also studied, range in age from late Atokan to early Desmoinesian.
 As in other coal basins, Lycospora, borne by lycopod trees, greatly dominates the lower and middle Atokan spore assemblages in coals and shale, but spores from ferns, especially tree ferns, significantly increase in abundance in the upper Atokan and lower Desmoinesian. The pattern of change of dominance among Lycospora pellucida, L. granulata, and L. micropapillata in middle Atokan (Westphalian B-C transition) that has been demonstrated earlier in the Illinois basin and eastern Kentucky and Tennessee, also occurs in eastern Kansas. At least 10 species of spores, which appeared in the middle Atokan in other parts of the equatorial coal belt, also appeared at this time in eastern Kansas. Most of these species have their affinities with the ferns, which were adapted to drier habitats than lycopods. Thus, the climate may have become a little drier in the equatorial coal belt during middle Atokan.

H2-rich and Hydrocarbon Gas Recovered in a Deep Precambrian Well in Northeastern Kansas

In late 2005 and early 2006, the WTW Operating, LLC (W.T.W. Oil Co., Inc.) #1 Wilson well (T.D. = 5772 ft; 1759.3 m) was drilled for 1826 ft (556.6 m) into Precambrian basement underlying the Forest City Basin in northeastern Kansas. Approximately 4500 of the 380,000 wells drilled in Kansas penetrate Precambrian basement. Except for two previous wells drilled into the arkoses and basalts of the 1.1-Ga Midcontinent Rift and another well drilled in 1929 in basement on the Nemaha Uplift east of the Midcontinent Rift, this well represents the deepest penetration into basement rocks in the state to date. Granite is the typical lithology observed in wells that penetrate the Precambrian in the northern Midcontinent. Although no cores were taken to definitively identify lithologies, well cuttings and petrophysical logs indicate that this well encountered basement metamorphic rocks consisting of schist, gneiss, and amphibolitic gneiss, all cut by aplite dikes. The well was cased and perforated in the Precambrian, and then acidized. After several days of swabbing operations, the well produced shows of low-Btu gas, dominated by the non-flammable component gases of nitrogen (20%), carbon dioxide (43%), and helium (1%). Combustible components include methane (26%), hydrogen (10%), and higher molecular-weight hydrocarbons (1%). Although Coveney and others [Am. Assoc. Petroleum Geologists Bull., v. 71, no, 1, p. 39–48, 1987] identified H2-rich gas in two wells located close to the Midcontinent Rift in eastern Kansas, this study indicates that high levels of H2 may be a more widespread phenomenon than previously thought. Unlike previous results, the gases in this study have a significant component of hydrocarbon gas, as well as H2, N2, and CO2. Although redox reactions between iron-bearing minerals and groundwater are a possible source of H2 in the Precambrian basement rocks, the hydrocarbon gas does not exhibit the characteristics typically associated with proposed abiogenic hydrocarbon gases from Precambrian Shield sites in Canada, Finland, and South Africa. Compositional and isotopic signatures for gas from the #1 Wilson well are consistent with a predominantly thermogenic origin, with possible mixing with a component of microbial gas. Given the geologic history of uplift and rifting this region, and the major fracture systems present in the basement, this hydrocarbon gas likely migrated from source rocks and reservoirs in the overlying Paleozoic sediments and is not evidence for abiogenic hydrocarbons generated in situ in the Precambrian basement.

Characterization of a Shallow Horizontal Fracturing Treatment in Western Missouri

This article, written by Assistant Technology Editor Karen Bybee, contains highlights of paper SPE 102342, "Characterization of a Shallow Horizontal Fracturing Treatment in Western Missouri," by L.K. Britt, SPE, NSI Technologies Inc.; S. Dunn- Norman, SPE, U. of Missouri-Rolla; M.B. Smith, SPE, NSI Technologies Inc.; E. Atekwana, U. of Missouri-Rolla; L. Slater, Rutgers U.; A. Gupta, SPE, and D. Numbere, SPE, U. of Missouri-Rolla; J.V. Fontana and J.H. Viellenave, Direct Geochemical; and J. Pelger, SPE, J-Environmental Inc., prepared for the 2006 SPE Annual Technical Conference and Exhibition, San Antonio, Texas, 24–27 September. A research project, sponsored by the U.S. Dept. of Energy, was undertaken to demonstrate a development method for the heavy-oil reserves that exist at ultrashallow depth in southwestern Missouri and southeastern Kansas. The principal objective was to demonstrate an economically viable method of producing the shallow heavy oil by use of a combination of microbial-enhanced oil-recovery treatments and horizontal fracturing in vertical wells. Introduction Heavy oil (8 to 25°API) exists in the shallow Pennsylvanian sands that occur over approximately 8,000 sq miles along the Kansas/Missouri border. The area covers portions of the northeast Oklahoma platform and the Cherokee and the Forest City basins. The Cherokee group is a sequence of alternating shales and sandstones with thin coal and limestone beds. The main productive units within the Cherokee group are the Bluejacket and Warner sandstones. The Warner sand has been drilled throughout Vernon County, Missouri, and several areas of known oil deposits have been defined. In the latter part of 2000, seven boreholes were continuously cored to a total depth (TD) of approximately 220 ft. All wells encountered heavy oil in both the Bluejacket and Warner sandstones. The Bluejacket sand occurred at approximately 130 to 135 ft with 8 to 12 ft of net pay, and the Warner sand occurred at approximately 160 to 170 ft with 15 to 30 ft of net pay. Warner-sand porosity ranged from 14 to 25%, and permeability in the Upper Warner ranged from 100 to 400 md. Five wells were drilled to produce the shallow heavy-oil deposits in the Warner sandstone, the Fauvergue Wells 1 through 5 (Fig. 1). The Cushard Wells 4 and 5 were cored wells in the project area. These wells were cored to TD and the cores analyzed as part of the project. Although it was believed that older wells drilled in the Warner sandstone had been fracture stimulated, no information regarding any historical fracture treatments, execution, or performance was available. Geomechanical Data Set The geomechanical data set includes profiles with depth of Young's modulus, in-situ stress, and fracture-fluid leakoff. Core from the Bluejacket and Warner sandstone formations and surrounding shales was available from the coreholes drilled, and static triaxial compression tests were conducted on samples to determine Young's modulus. Evaluation of the triaxial compression tests indicated that the Bluejacket and Warner sandstones have an average Young's modulus of 3.1×106 and 1.3×106 psi, respectively. The Rowe coal and the bounding shales have an average Young's modulus of 2.0×106 and 1.8×106 psi, respectively.

Origin and development of plains-type folds in the mid-continent (United States) during the late Paleozoic

Plains-type folds are local, subtle anticlines formed in the thin sedimentary package overlying a shallow, crystalline basement on the craton. They are small in areal extent (usually less than 1–3 km2 [0.4–1.2 mi2]), and their amplitude increases with depth (usually tens of meters), which is mainly the result of differential compaction of sediments (usually clastic units) over tilted, rigid, basement fault blocks. The development of these structural features by continuous but intermittent movement of the basement fault blocks in the late Paleozoic in the United States mid-continent is substantiated by a record of stratigraphic and sedimentological evidence.The recurrent structural movement, which reflects adjustment to external stresses, is expressed by the change in thickness of stratigraphic units over the crest of the fold compared to the flanks. By plotting the change in thickness for different stratigraphic units of anticlines on different fault blocks, it is possible to determine the timing of movement of the blocks that reflect structural adjustment. These readjustments are confirmed by sedimentological evidence, such as convolute, soft-sediment deformation features and small intraformational faults.The stratigraphic interval change in thickness for numerous structures in the Cherokee, Forest City, and Salina basins and on the Nemaha anticline of the mid-continent United States was determined and compared for location and timing of the adjustments. Most of the adjustment occurred during and after time of deposition of the Permian–Pennsylvanian clastic units, which, in turn, reflect tectonic disturbance in adjacent areas, and the largest amount of movement on the plains-type structures occurred on those nearest and semiparallel to major positive features, such as the Nemaha anticline.Depending on the time of origin and development of plains-type folds, they may control the entrapment and occurrence of oil and gas.

Tectonic Framework of the Southwestern Margin of the Illinois Basin and Its Influence on Neotectonism and Seismicity

Structures in Phanerozoic rocks along the southwestern margin of the intracratonic Illinois basin vary in deformational styles and orientations. These variations have been inherited from the Proterozoic basement. Based on them, a tectonic framework is developed that divides the margin into three tectonic domains separated by two northeast-trending zones of accommodation. Both zones of accommodation are interpreted as major Proterozoic crustal boundaries that have partitioned strain throughout the Phanerozoic. Each tectonic domain has a distinct neotectonic and seismic history, which is also attributable to strain partitioning along the zones of accommodation. The northern tectonic domain constitutes part of the Mississippi River arch, which lies north of St. Louis, Missouri. This arch separates the northern part of the Illinois basin from the Forest City basin to the west and contains faulted, asymmetrical anticlines and monoclines that have high structural relief, and broad anticlines and synclines that have low structural relief. Structural trends range from north-northwest to west-northwest. These structures underwent multiple Paleozoic deformations but have been mostly inactive since the late Paleozoic. There are few suggestions of any neotectonic activity in this domain and very little seismicity during the past 25 years. The northeast-trending St. Charles lineament (SCL) is a zone of accommodation that separates the northern and central tectonic domains. The SCL coincides with an extensive Proterozoic crustal boundary as defined by Nd geochemistry, across which basement rocks of differing lithologies and ages are juxtaposed. This crustal boundary is interpreted as a possible ancient transform fault. Locally, strike-slip faulting occurred along the SCL, probably in the late Paleozoic. Possible neotectonism occurred along the SCL, as well as some recent light to very minor seismicity. The central tectonic domain lies between the two zones of accommodation and contains complex fault systems that trend prominently northwest. Geologic mapping and structural analysis document a complex history of episodic left-lateral strike-slip and reverse faulting during the Paleozoic. Some of these faults may be branches of a deeply rooted flower structure in the crust and may have influenced the emplacement of ultramafic diatremes in the Devonian. Neotectonic features are localized in the southern part of this domain. Recorded seismicity is scattered throughout the central tectonic domain, but is more concentrated in the southeastern half. The Commerce geophysical lineament (CGL) is a northeast-trending feature that extends from northeastern Arkansas to at least Vincennes, Indiana. It is a zone of accommodation between the central and southern tectonic domains. This feature has been interpreted to consist of en-echelon faults and igneous intrusions in the basement that are related to the Neoproterozoic to early Paleozoic Reelfoot rift; however, it is postulated to have an even older ancestry. In the Thebes Gap area of Missouri and Illinois, a well developed system of northeast-to-north-northeast-trending, strike-slip faults occurs directly over the CGL. These faults cut Paleozoic, Mesozoic, and Cenozoic formations and have had a long-lived and episodic tectonic history, including Pleistocene and Holocene activity. In the past 25 years, several dozen light to minor earthquakes ( mb 2-4) have occurred on, or adjacent to, the CGL. The southern tectonic domain is roughly equivalent to the northern Mississippi embayment and contains many northeast-trending faults related to the Reelfoot rift. This domain also contains the New Madrid seismic zone, the most seismically active area east of the Rocky Mountains and the site of historical great earthquakes. During the late Paleozoic, uplift of the broad northwest-trending Pascola arch, which directly overlies the Mesoproterozoic Missouri batholith, closed the southwestern margin of the Illinois basin from its connection to the Arkoma basin. This uplifted arch extends across the central and southern tectonic domains and is partitioned also by the CGL. We propose a model in which the New Madrid seismic zone is a descendant of similar, intense, late Paleozoic tectonism that was concentrated in the southern domain at the intersection of the Pascola arch and the Reelfoot rift.

Origin of illite in the lower Paleozoic of the Illinois basin: Evidence for brine migrations

In the lower Paleozoic of the Illinois Basin, three illite polytypes are found: 2M 1 of detrital origin, and 1M d and 1M of diagenetic origin. Illite polytype quantification of detrital 2M 1 illite and diagenetic 1M d and 1M illite, combined with K-Ar age dating, allows extrapolation to apparent detrital and diagenetic illite ages. Kinetic modeling of smectite illitization, combined with the calculated age of illitization, can evaluate different origins of illite. The diagenetic illite in the lower Paleozoic of the Illinois Basin is interpreted not to have formed solely by burial diagenesis but mainly during multiple brine events. The Upper Ordovician Maquoketa Group contains diagenetic illite (dominantly 1M d with minor 1M ) with an extrapolated age of ∼360 m.y. (356–377 m.y.) and formed from smectite at temperatures of 50–100 °C. This age falls within the span of dates for illite/smectite (I/S) in K-bentonites from the Upper Mississippi Valley and is interpreted to be a combined result of illitization by burial diagenesis and either a hydrothermal brine from the southern and deeper part of the basin or a K-rich brine from the Michigan Basin, Upper Mississippi Valley area, or Forest City Basin. In Ordovician and Cambrian shale partings and sandstone older than the Maquoketa Group, the diagenetic illite ( 1M d in shale and 1M in sandstone) has an age of ∼300 m.y. and formed at temperatures <140 °C. This late Paleozoic age falls within the range of illites from sandstone in the Upper Mississippi Valley and K-bentonites of the Appalachian Basin; it coincides with the Alleghany orogeny and is interpreted as having formed by gravity-driven flow from the uplifted Alleghanian-Ouachita orogenic belt that drove hot (<140 °C) fluids through the Illinois Basin.

A Petroleum System for the Salina Basin in Kansas Based on Organic Geochemistry and Geologic Analog

The Salina Basin historically has been an “exploration desert”—a home of dryholes. Although this basin, which underlies much of north-central Kansas, may never be a prolific source of hydrocarbons, recent research into the maturation and geochemistry of organic matter and oils in Kansas can provide guidelines for a new exploration strategy. The Salina Basin is similar to the oil-productive Forest City Basin in northeastern Kansas in many ways. Both basins originated as a single large basin (i.e., the North Kansas Basin) prior to the rise of the Nemaha Uplift in Late Mississippian-Early Pennsylvanian time. Their Paleozoic stratigraphy thus is similar and the axes of both basins are presently at approximately the same depth. Thermal maturation modeling and available organic-matter maturation data indicate that the lower Paleozoic rocks in the axes of both basins are in the early stages of oil generation. In the Forest City Basin the Ordovician Simpson Group is the deepest known hydrocarbon source-rock—oil-reservoir interval, and by analogy, exploration tests in the Salina Basin, at a minimum, should penetrate through this stratigraphic interval. Ordovician Simpson Group shales in the Forest City Basin are the source rocks for a geochemically distinct oil, which also occurs in Ordovician reservoirs in the extreme southern end of the Salina Basin. To increase the odds of success in an exploration program in the Salina Basin, wildcat wells should be drilled where thermal maturation is greatest. The broad NW–SE-trending basin axis is the most logical area. Exploration tests along this axis in the northern end of the basin may have an extra advantage as organic matter in the Simpson Group may be more thermally mature because of greater burial depth during the Cretaceous. Along the eastern margin of the nearby Central Kansas Uplift and Pratt Anticline, several Paleozoic geologic structures, some of which contain major oil fields, are attributable to tectonic reactivation along the western margin of the Precambrian Central North American Rift System (CNARS). Prospective structural trends in the Paleozoic section of the Salina Basin are anticipated to be associated with this underlying tectonic boundary. The western margin of the CNARS trends NNE–SSW where it passes under the axis of the Salina Basin in northeastern Lincoln and southeastern Mitchell counties. This area is sparsely drilled, with less than two tests per township. If an exploration program can define lower Paleozoic structural closures in this region, these structures may represent the best chance for future petroleum discoveries.

Paleosol in Galesburg Formation (Kansas City Group, Upper Pennsylvanian), northern Midcontinent, U.S.A.; evidence for climate change and mechanisms of marine transgression

ABSTRACT A widespread paleosol in the Galesburg Formation (Kansas City Group, Missourian) in the northern Midcontinent Upper Pennsylvanian cyclothem (MUPC) outcrop belt exhibits prominent features, including repeating sets of synformal slickensides and mukkara or chimney structures, which characterize it as a paleo-Vertisol. The Galesburg paleosol has pervasive low-chroma grayish to greenish coloration, an organic-matter profile, and geochemical characteristics with regard to S, Fe2O3, MnO, SiO2, and Al2O3 that indicate wetter soil conditions than those indicated by equally widespread high-chroma paleosols higher in the local stratigraphic succession (particularly a high-chroma paleo-Vertisol in the upper Lawrence Formation). The predominance of low-chroma (i.e., wetter) paleosols throughout the Kansas City Group in the northern Forest City Basin (southeastern Nebraska and southwestern Iowa), as exemplified by the Galesburg paleosol, compared to the greater frequency of high-chroma (i.e., drier) paleosols in overlying Pennsylvanian (especially Virgilian) strata, implicates decreasing rainfall in the interior of North America during the late Missourian. The variability in rainfall through this Missourian-Virgilian shift need not have exceeded the range of rainfall (400-1400 mm/a) associated with modern soil analogs in subtropical to warm-temperate North America. Thus, there is an indication of climate change on a longer-term time scale ( 105-106 a) than the intra- or inter-eustatic-cycle climate change proposed by other authors for late Paleozoic cyclothems in the North American interior. Regional differences in the nature of transgressive marine strata directly above the Galesburg further suggest: (1) that important information relevant to reconstruction of the sea-level curve is probably missing from the interval between regressive paleosols and subsequent regressive limestones in MUPCs, and (2) that there were probably appreciable differences in the overall mechanism of deposition of MUPC transgressive shales and black core shales within any particular interval of MUPC transgressive deposition.

Abstract: Analysis of Structural Controls on the Development of the Upper Pennsylvanian Tonganoxie Incised Paleovalley System of Northeast Kansas&amp;nbsp;

Abstract The paleotectonic setting of the Tonganoxie Sandstone (Upper Pennsylvanian, Virgilian) incised-valley system in the Forest City Basin of northeastern Kansas was analyzed using isopachous maps of the stratigraphic interval containing the paleovalley-fill and lineaments maps based on previous analyses of the configuration of the present-day Precambrian basement. Because structure maps of the present-day configuration of the Tonganoxie Sandstone reveal nothing about the structural framework that influenced paleovalley erosion and sedimentation during the Pennsylvanian, isopachous maps were used to detect subtle changes in local topography. These local topographic changes were the result in part of concurrent structural displacements. Isopachous maps of intervals bounding and containing the Tonganoxie Sandstone were compared with lineaments interpreted from a map of the 2nd-order trend residuals of the basement gravity-field intensity and a map of the configuration of the present-day Precambrian surface. Previous studies along the eastern portion of the Tonganoxie paleovalley system used isopachous maps to identify a large trunk valley with smaller tributary valleys exhibiting a rectilinear or trellised drainage. Persistent linear thickness trends were recognized that coincide with the trends of interpreted lineaments. The coincidence of these trends suggests that Upper Pennsylvanian structures that influenced the location of paleovalley incisions were developed when preexisting basement faults were reactivated. The reactivation of these basement faults may have occurred in response to the Ouachita tectonic event far south of the Forest City Basin. Variations in thickness of these stratigraphic intervals are related, in part, to differential subsidence within distinct multi-km scale structural blocks with boundaries oriented predominately northwest-southeast and southwest-northeast. Movement along the structural blocks caused differential subsidence and influenced the subsequent drainage pattern of the Tonganoxie paleovalley. The results of this study suggest that exploration for incised valleys should focus on regional mapping of stratigraphic intervals that enclose the valleys and related basement information to delineate structural blocks that may have influenced the locations of valley incisions.

Abstract: Forest City Basin Coal-Bed Methane Potential, Northeastern Kansas and Western Missouri&amp;nbsp;

Abstract: Forest City Basin Coal-Bed Methane Potential, Northeastern Kansas and Western Missouri&amp;nbsp;

Abstract: Coal Resources and Coalbed Methane Potential in the Kansas Portion of the Forest City Basin&nbsp;

Abstract: Coal Resources and Coalbed Methane Potential in the Kansas Portion of the Forest City Basin&nbsp;

Abstract: Geochemistry of Oils and Hydrocarbon Source Rocks, Forest City Basin, Northeastern Kansas and Adjacent Areas in Missouri, Iowa and Nebraska&amp;nbsp;

Abstract: Geochemistry of Oils and Hydrocarbon Source Rocks, Forest City Basin, Northeastern Kansas and Adjacent Areas in Missouri, Iowa and Nebraska&amp;nbsp;

Tectonic and paleoclimatic significance of a prominent upper Pennsylvanian (Virgilian/Stephanian) weathering profile, Iowa and Nebraska, USA

Abstract A Virgilian (Stephanian) weathering profile up to 4 m deep, containing a paleosol (basal Rakes Creek paleosol) in the basal mudstone of the Rakes Creek Member and karstified marine sediments in the Ost, Kenosha, and Avoca members below, is restricted to southeastern Nebraska (specifically the Weeping Water Valley) and the Missouri River Valley bluffs of adjacent easternmost Iowa. This weathering profile, informally referred to as the Weeping Water weathering profile, disappears farther eastward into the shallow Forest City Basin in southwestern Iowa. Weeping Water weathering profile features are prominent in comparison to other Midcontinent Pennsylvanian subaerial exposure surfaces, indicating prolonged subaerial exposure, relatively high elevation, and a marked drop in water table along the Nemaha Uplift in southeastern Nebraska. Eastward, on the margin of the Forest City Basin, the basal Rakes Creek paleosol and underlying karst are thinner and relatively poorly developed; paleosol characteristics indicate formation on lower landscape positions. Comparative pedology, the contrasting of paleosol variability, morphology, and micromorphology between different paleosols in the same regional succession, provides a basis for interpreting the larger significance of the basal Rakes Creek paleosol. The stratigraphically older upper Lawrence and Snyderville paleosols in the same area are significantly different in patterns of lateral variability and overall soil characteristics. Weaker eustatic control and stronger tectonic activity may explain the greater west-east variability (and eventual eastward disappearance) of the basal Rakes Creek paleosol. Differences in soil characteristics between the Vertisol-like upper Lawrence and Snyderville paleosols and the non-Vertisol-like basal Rakes Creek paleosol appear to be due to climate change, particularly a shift from more seasonal to more uniform rainfall. This climate change hypothesis is compatible with overall Virgilian stratigraphic trends in the northern Midcontinent outcrop area.

Subsurface Temperature Anomalies as a Key to Petroleum-Producing Areas in the Cherokee and Forest City Basins, Eastern Kansas?: ABSTRACT

The relation of subsurface temperature to `plain-type fold` structure in the Midcontinent (USA) as an exploration tool has been speculated on for a long time. Structural highs, termed `plains-type folds,` are partly the result of differential compaction of sediments over rigid crystalline fault blocks in the Precambrian basement. In the Midcontinent, bottom-hole temperature (BHT) data, temperatures measured in drillstem tests (DSTs), and structural data are abundant. In the Cherokee and Forest City Basins, we analyzed BHT data by depth and stratigraphic unit (Cambro-Ordovician Arbuckle carbonates; Mississippian carbonates; and Perm-Pennsylvanian clastics). By relating the BHTs to DSTs, it was noted that the thermal disturbance inherent in BHT by drilling is minor and comparable within a formation. Also, the signal-noise ratio of BHTs could be improved utilizing the large data set. Although the resulting BHT formation gradients show unexpected values from the thermal conductivity in the carbonates and from the evaluated temperature disturbance by the drilling process, analysis of the BHT spatial pattern shows a coincidence of structural highs and temperature anomalies both in the clastics and in the carbonates. These BHT anomalies are outlined by values higher than the regional temperature trend. We attribute the anomalies partly to the insulation effectmore » of petroleum (which may include the self-generation of heat) and partly to the movement of fluids vertically through the fracture and fault system created in the sedimentary veneer. Numerous examples from the oil- and gas-producing areas in eastern Kansas show that the nature of origin of fluids contained in a porous medium can alter local geothermal conditions.« less