Ouachita Thrust Belt Research Articles

Full Waveform Ambient Noise Tomography for the Northern Mississippi Embayment

AbstractWe use seismic ambient noise data recorded by broadband stations around the northern Mississippi Embayment to develop a three‐dimensional shear wave velocity model with full waveform inversion. Empirical Green's functions at periods between 8 and 40s are extracted using a data processing flow based on the continuous wavelet transform. Synthetic waveforms are calculated with an isotropic model through a Graphics Processor Unit‐enabled, collocated finite‐difference code. Starting from the Central United States Velocity Model, the shear wave velocity is iteratively updated with sensitivity kernels constructed using the adjoint method. Several mid‐crustal velocity variations are related to major geological features including the Mississippi Valley graben (MVG), the Ouachita thrust belt, and the Missouri batholith. An intrusion is imaged in northwestern Alabama, coincident with a previously unexplained gravity high. A major change in mid‐crustal velocity occurs across the MVG; much higher velocity crust is present southeast of the graben than northwest. The high velocities are attributed to numerous igneous intrusions, possibly related to formation of the Granite‐Rhyolite province. A strength contrast produced by the change in mid‐crustal velocities may have facilitated formation of the younger, shallower MVG, as external stresses became tensional during Iapetus rifting. The rift pillow is interpreted as the deeper expression of the high velocity crust. Low velocity crust is present below southern Missouri starting at a depth of roughly 20 km. The boundary between the low velocity crust and higher velocity crust to the south and east is sharp and coincides with the Nd‐line.

Detrital zircon geothermochronology reveals pre-Alleghanian exhumation of regional Mississippian sediment sources in the southern Appalachian Valley and Ridge Province

AbstractThe Black Warrior foreland basin records sedimentation associated with the development of intersecting Ouachita and Alleghanian thrust belts along the southern margin of Laurentia. Mississippian–Pennsylvanian units in the Black Warrior basin are interpreted to be sourced from either the northern Appalachians and mid-continent or more regionally from the southern Appalachians or nearby Ouachita thrust belt. We present detrital zircon U-Pb ages and Th/U values from Paleozoic units that indicate zircon from the Mississippian Hartselle Sandstone are temporally and chemically compatible with being sourced from the southern Appalachians. Zircon mixing models suggest sediment was primarily recycled from Cambrian, Ordovician, and Devonian strata in the Appalachian Valley and Ridge, with minor influx from Piedmont units. A ca. 415 Ma zircon population requires additional input from the Maya Block of the Yucatan Peninsula or similar outboard terranes. We present zircon (U-Th)/He analysis and thermal history modeling of Paleozoic units, which detail pre-Alleghanian exhumation in the Appalachian Valley and Ridge. Both the Cambrian Chilhowee Group and Pennsylvanian Pottsville Formation exhibit (U-Th)/He dates ranging from 507 to 263 Ma with a Mississippian subset (353–329 Ma, n = 4), which indicates rapid cooling and inferred exhumation during Late Devonian–Early Mississippian Neoacadian tectonism. We propose a Mississippian drainage system that transported material along southern Appalachian structural fabrics to the juncture between Appalachian and Ouachita thrust belts followed by a sediment-routing rotation toward the Black Warrior foreland. This interpretation honors chemical-age zircon data, accounts for metamorphic grains in thin section petrography, and matches Mississippian–Pennsylvanian Black Warrior foreland lithostratigraphic relationships.

Detrital-zircon analyses, provenance, and late Paleozoic sediment dispersal in the context of tectonic evolution of the Ouachita orogen

Abstract New analyses for U-Pb ages and εHft values, along with previously published U-Pb ages, from Mississippian–Permian sandstones in synorogenic clastic wedges of the Ouachita foreland and nearby intracratonic basins support new interpretations of provenance and sediment dispersal along the southern Midcontinent of North America. Recently published U-Pb and Hf data from the Marathon foreland confirm a provenance in the accreted Coahuila terrane, which has distinctive Amazonia/Gondwana characteristics. Data from Pennsylvanian–Permian sandstones in the Fort Worth basin, along the southern arm of the Ouachita thrust belt, are nearly identical to those from the Marathon foreland, strongly indicating the same or a similar provenance. The accreted Sabine terrane, which is documented by geophysical data, is in close proximity to the Coahuila terrane, suggesting the two are parts of an originally larger Gondwanan terrane. The available data suggest that the Sabine terrane is a Gondwanan terrane that was the provenance of the detritus in the Fort Worth basin. Detrital-zircon data from Permian sandstones in the intracratonic Anadarko basin are very similar to those from the Fort Worth basin and Marathon foreland, indicating sediment dispersal from the Coahuila and/or Sabine terranes within the Ouachita orogen cratonward from the immediate forelands onto the southern craton. Similar, previously published data from the Permian basin suggest widespread distribution from the Ouachita orogen. In contrast to the other basins along the Ouachita-Marathon foreland, the Mississippian–Pennsylvanian sandstones in the Arkoma basin contain a more diverse distribution of detrital-zircon ages, indicating mixed dispersal pathways of sediment from multiple provenances. Some of the Arkoma sandstones have U-Pb age distributions like those of the Fort Worth and Marathon forelands. In contrast, other sandstones, especially those with paleocurrent and paleogeographic indicators of southward progradation of depositional systems onto the northern distal shelf of the Arkoma basin, have U-Pb age distributions and εHft values like those of the “Appalachian signature.” The combined data suggest a mixture of detritus from the proximal Sabine terrane/Ouachita orogenic belt with detritus routed through the Appalachian basin via the southern Illinois basin to the distal Arkoma basin. The Arkoma basin evidently marks the southwestern extent of Appalachian-derived detritus along the Ouachita-Marathon foreland and the transition southwestward to overfilled basins that spread detritus onto the southern craton from the Ouachita-Marathon orogen, including accreted Gondwanan terranes.

A multidisciplinary approach in determining the maceral (kerogen type) and mineralogical composition of Upper Cretaceous Eagle Ford Formation: Impact on pore development and pore size distribution

Maceral (kerogen or organic matter type) and mineralogical composition with the associated porosity of the Upper Cretaceous Eagle Ford Formation, Karnes County, Texas was investigated. In Karnes County, the calcareous mudstone of the Eagle Ford Formation was deposited in an open marine outer shelf to upper slope environment. To adequately characterise all components of this mudrock, a multidisciplinary approach was implemented to analyse 26 core samples from a single producing well that completed within the Eagle Ford Formation. Analyses included organic petrology, organic geochemistry, light and electron microscopy (and spectroscopy), pore size distribution analyses and X-ray diffraction. The bitumen reflectance ranges between 1.94 and 2.08% (calculated VRo=1.60–1.69%) indicating the mudrock is in the condensate-rich gas window. The TOC content ranges between 1.7% and 7.2% with an average of 3.9%. Mineral composition is dominated in descending order by calcite, clay, quartz and plagioclase. Calcite varies between 32% and 87% with an average of 57%. Porosity measured by helium pycnometry ranges between 3.5 and 10.3% with an average of 7.5%. Organic petrology coupled with backscattered and field emission scanning electron microscopy indicates matrix bitumen as the most significant contributor to the TOC content and porosity. Matrix bitumen contains significant meso- and microporosity and is enhanced by the secondary cracking of the bitumen. An increase in bioclastic (mostly foraminifera) and siliciclastic components correlates with lower TOC content due to the lower volume of organic-rich matrix. Peloids (fecal pellets) are calcareous, organic rich and lack terrigenous sediment indicating a zooplankton source. Pelagic deposition of peloids is interpreted as a primary mechanism of amorphinite deposition which is converted to hydrocarbons and matrix bitumen. The mixed siliciclastic calcareous matrix that surrounds the peloids is comprised of matrix bitumen and dispersed organics from land plants (vitrinite, fusinite and inertodetrinite). The siliciclastic component increases in the middle of the Eagle Ford and marks the boundary (maximum flooding surface) between the lower (TST) and upper (HST) section of the formation. The inorganic and organic components suggest a mixed terrigenous and marine source with both inorganic and organic sediments being derived from the proximal Ouachita thrust belt and from pelagic organisms within the overlying water column. The lower (TST) Eagle Ford Formation contains more micro- and mesopores than the upper (HST) Eagle Ford Formation due to higher TOC content in the lower Eagle Formation. These results illustrate that a multidisciplinary approach is necessary to identify how pore network are distributed within mudrocks and how this distribution is controlled by organic/inorganic deposition and hydrocarbon generation processes.

Heat Flow and Geothermal Potential in the South-Central United States

Geothermal exploration is typically limited to high-grade hydrothermal reservoirs that are usually found in the western United States, yet large areas with subsurface temperatures above 150°C at economic drilling depths can be found east of the Rocky Mountains. The object of this paper is to present new heat flow data and to evaluate the geothermal potential of Texas and adjacent areas. The new data show that, west of the Ouachita Thrust Belt, the heat flow values are lower than east of the fault zone. Basement heat flow values for the Palo Duro and Fort Worth Basins are below 50 mW/m2 while, in the frontal zone of the belt, they can exceed 60 mW/m2. Further east, along the Balcones fault system the heat flow is in general higher than 55 mW/m2. The eastern most heat flow sites are in Louisiana and they show very high heat flow (over 80 mW/m2), which is associated with the apparently highly radioactive basement of the Sabine uplift. The geothermal resource in this area is large and diverse, and can be divided in high grade (temperature above 150°C) convective systems, conductive based enhanced geothermal systems and geothermal/geopressured systems. One of the most attractive areas east of the cordillera extends from eastern Texas across Louisiana and Arkansas to western Mississippi. Here temperatures reach exploitation range at depths below 4 km, and tapping such a resource from shut in hydrocarbon fields is relatively easy. The initial costs of the development can be greatly reduced if existing hydrocarbon infrastructure is used, and therefore using shut-in hydrocarbon fields for geothermal purposes should not be neglected.

Structural style of the Marathon thrust belt, West Texas

The Marathon portion of the Ouachita thrust belt consists of a highly deformed allochthonous wedge of Cambrian-Pennsylvanian slope strata (Marathon facies) that was transported to the northwest and emplaced over Pennsylvanian foredeep sediments. The foredeep strata in turn overlie early-middle Paleozoic shelfal sediments which are deformed by late Paleozoic basement-involved reverse faults. The Dugout Creek thrust is the basal thrust of the allochthon. Shortening in this sheet and overlying sheets is ∼80%. Steep imbricate faults link the Dugout Creek thrust to upper level detachments forming complex duplex zones. Progressive thrusting and shortening within the allochthon folded the upper level detachments and associated thrust sheets. The Caballos Novaculite is the most competent unit within the Marathon facies and controlled development of prominent detachment folds. Deeper imbricate sheets composed of the Late Pennsylvanian foredeep strata, and possibly early-middle Paleozoic shelfal sediments developed concurrently with emplacement of the Marathon allochthon and folded the overlying allochthon. Following termination of thrusting in the earliest Permian, subsidence and deposition shifted northward to the Delaware, Midland and Val Verde foreland basins.

Tectonic geomorphology of the southeastern Mississippi Embayment in northern Mississippi, USA

We analyzed drainage-basin geometry in part of the southeastern Mississippi Embayment near the New Madrid seismic zone in order to detect areas of lateral stream migration that could indicate recent tectonism. Toward this goal, a field of drainage-basin asymmetry vectors was generated from a digital terrain model and compared to geologic structure, lithofacies, seismicity, remotely sensed lineaments, and major drainage divides. Transverse topographical drainage-basin asymmetry (T-index) results define geomorphic domains in northern Mississippi (33° to 35°N, 88.5° to 90.25°W) that may reflect deep crustal blocks bounded by active faults or flexures. T-index measurements (a proxy for lateral stream migration) of more than 4500 second-order drainage basins produced a two-dimensional field of 282 spatially averaged vectors from which we interpreted 12 domains. Some domain boundaries correspond to mapped faults of two Paleozoic fault systems in our study area, the northeast-striking Mississippi Valley graben system and the northwest-striking Ouachita thrust belt and foreland faults. Several other prominent domain boundaries may be previously unmapped faults (flexures?) parallel to these systems. This interpretation is supported by satellite image analysis of the northeastern study area, which reveals lineaments consistent with our domain boundaries that have strikes that reflect the regional subsurface structural grain.

Tectonic geomorphology of the southeastern Mississippi Embayment in northern Mississippi, USA

Research Article| September 01, 2006 Tectonic geomorphology of the southeastern Mississippi Embayment in northern Mississippi, USA Julio Garrote; Julio Garrote 1Department Geodinamica, Faculty Geología, Universidad Complutense de Madrid, Av. Complutense s/n, 28040 Madrid, Spain Search for other works by this author on: GSW Google Scholar Randel Tom Cox; Randel Tom Cox 2Earth Sciences Department, G-1 Johnson Hall, University of Memphis, Memphis, Tennessee 38152, USA Search for other works by this author on: GSW Google Scholar Charles Swann; Charles Swann 3Mississippi Mineral Resources Institute, 220 Old Chemistry Building, University of Mississippi, University, Mississippi 38677, USA Search for other works by this author on: GSW Google Scholar Michael Ellis Michael Ellis 4Center for Earthquake Research and Information, University of Memphis, Memphis, Tennessee 38152, USA Search for other works by this author on: GSW Google Scholar GSA Bulletin (2006) 118 (9-10): 1160–1170. https://doi.org/10.1130/B25721.1 Article history received: 14 Sep 2004 rev-recd: 03 Apr 2006 accepted: 18 Apr 2006 first online: 08 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation Julio Garrote, Randel Tom Cox, Charles Swann, Michael Ellis; Tectonic geomorphology of the southeastern Mississippi Embayment in northern Mississippi, USA. GSA Bulletin 2006;; 118 (9-10): 1160–1170. doi: https://doi.org/10.1130/B25721.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract We analyzed drainage-basin geometry in part of the southeastern Mississippi Embayment near the New Madrid seismic zone in order to detect areas of lateral stream migration that could indicate recent tectonism. Toward this goal, a field of drainage-basin asymmetry vectors was generated from a digital terrain model and compared to geologic structure, lithofacies, seismicity, remotely sensed lineaments, and major drainage divides.Transverse topographical drainage-basin asymmetry (T-index) results define geomorphic domains in northern Mississippi (33° to 35°N, 88.5° to 90.25°W) that may reflect deep crustal blocks bounded by active faults or flexures. T-index measurements (a proxy for lateral stream migration) of more than 4500 second-order drainage basins produced a two-dimensional field of 282 spatially averaged vectors from which we interpreted 12 domains. Some domain boundaries correspond to mapped faults of two Paleozoic fault systems in our study area, the northeast-striking Mississippi Valley graben system and the northwest-striking Ouachita thrust belt and foreland faults. Several other prominent domain boundaries may be previously unmapped faults (flexures?) parallel to these systems. This interpretation is supported by satellite image analysis of the northeastern study area, which reveals lineaments consistent with our domain boundaries that have strikes that reflect the regional subsurface structural grain. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Sedimentologic Role of Microproblematica Donezella in a Lower Pennsylvania Donezella-Siliceous Sponge-Dominated Carbonate Buildup, Frontal Ouachita Thrust Belt, Oklahoma, U.S.A.

Abstract The problematic organism Donezella emerged worldwide as one of the main carbonate mound builders in the middle Carboniferous. Donezella is composed of thin (70–160 μm in diameter), bifurcating (45 to 90 degrees) tubes. Microfacies analysis of a Donezella buildup from the Wapanucka Formation, Frontal Ouachita thrust belt, Oklahoma, U.S.A., was undertaken to examine the role of Donezella in a carbonate buildup. Donezella is the predominant biotic component of the Wapanucka buildup, and the buildup is composed of irregular pockets of boundstone dominated by Donezella, worm tubes, peloids and micritic crusts, siliceous sponge spicules, less common siliceous sponge boundstone, and peloidal wackestone with other bioclasts. In the lower part of the buildup, Donezella colonies are robust, convex upward, and up to several centimeters in diameter. These colonies are composed of delicately branching Donezella with an enclosed constructional pore system. These robust, upward-growing Donezella structures formed a substrate for other binders; therefore it appears that, on a microscale, Donezella, together with siliceous sponges and worm tubes, played the role of a constructor. Donezella occurs as a long, semicontinuous row of thalli when encrusting other framework grains, and encrusts siliceous sponges, Donezella colonies, corals, and worm tubes; thus, it also acted as a member of the binder guild. Deciphering these various roles of Donezella is a crucial first step toward documenting a possible spectrum of Donezella-dominated lithologies that constitute key elements in carbonate buildups in the Early to Middle Pennsylvanian.

Genetic relationship of rift-stage crustal structure, terrane accretion, and foreland tectonics along the southern Appalachian-Ouachita orogen

Abrupt along-strike variations in tectonostratigraphic composition, internal structural style, and detachment level in the southern Appalachian and Ouachita foreland thrust belts are defined at a large-scale bend in strike and a truncation of Ouachita structures by the frontal Appalachian thrust fault. The along-strike variations correspond to differences in the pre-orogenic rifted Laurentian margin, in the history and nature of terrane accretion, and in the response of the foreland to these differences. Within the Ouachita embayment of the Laurentian margin, diachronous arc-continent collision migrated northwestward along a rift-stage transform margin from the Black Warrior foreland basin on the southeast in Late Mississippian time to a short-wavelength, high-amplitude foreland basin (Arkoma basin) on the northwest in front of the Ouachita thrust-belt salient in Early-Middle Pennsylvanian time. Off-shelf, deep-water strata of both passive-margin and synorogenic facies comprise an accretionary prism and subduction complex, and the Ouachita allochthon consists of mud-dominated thrust sheets that are internally disharmonic and folded. The allochthon of off-shelf strata was thrust over the passive-margin carbonate shelf, which remains in the Ouachita footwall. Along the southeast side of the Alabama promontory of the Laurentian margin, passive-margin shelf carbonates are imbricated in the Appalachian thrust belt, which is characterized by internally coherent thrust sheets and high-amplitude frontal ramps. The palinspastic extent of shelf-carbonate rocks corresponds to the extent of structurally shallow basement rocks on the upper-plate rift-stage margin of the Alabama promontory of Laurentian crust. Terranes accreted to the Laurentian margin during the Taconic and Acadian orogenies were driven over the shallow basement by continent-continent collision of Laurentia with Africa (Gondwana). Emplacement of the thrust-translated terranes tectonically stripped and replaced the shelf carbonate. The frontal thrust fault of the Appalachian thrust belt truncates the southeastern end of the slightly older frontal Ouachita thrust belt, as well as the southeastern part of the greater Black Warrior basin in the Ouachita foreland. Shallow basement beneath the Appalachian thrust belt extends cratonward beneath the low-amplitude Appalachian foreland basin.

Sequential filling of a late Paleozoic foreland basin

ABSTRACT Through the use of an extensive data base of geophysical well logs, parasequence-scale subdivisions within a late Paleozoic synorogenic clastic wedge resolve cycles of sequential subsidence of a foreland basin, sediment progradation, subsidence of a carbonate shelf edge, diachronously subsiding discrete depositional centers, and basinwide transgression. Although temporal resolution of biostratigraphic markers is less precise in Paleozoic successions than in younger basins, parasequence-scale subdivisions provide more detailed resolution within marker-defined units in Paleozoic strata. As an example, the late Paleozoic Black Warrior basin in the foreland of the Ouachita thrust belt is filled with a synorogenic clastic wedge, the lower part of which intertongues with the fringe of a cratonic carbonate facies in the distal part of the basin. The stratal geometry of one tongue of the carbonate facies (lower tongue of Bangor Limestone) defines a ramp that grades basinward into a thin black shale. An overlying tongue of the synorogenic clastic wedge (lower tongue of Parkwood Formation) consists of cyclic delta and delta-front deposits, in which parasequences are defined by marine-flooding surfaces above coarsening- and shallowing-upward successions of mudstone and sandstone. Within the lower Parkwood tongue, two genetic stratigraphic sequences (A and B) are defined by parasequence offlap and downlap patterns and are bounded at the tops by basinwide maximum-flooding surfaces. The distribution of parasequences within sequences A and B indicates two cycles of sequential subsidence (deepening) and progradation, suggesting subsidence during thrust advance and progradation during thrust quiescence. Parasequence stacking in sequences A and B also indicates diachronous differential tectonic subsidence of two discrete depositional centers within the basin. The uppermost sequence (C) includes reworked sandstones and an overlying shallow-marine limestone, a vertical succession that reflects no tectonic subsidence, a very minor or null sediment supply, and basinwide transgression. The temporal resolution at parasequence scale significantly improves the resolution of the tectonic history of the thrust belt-foreland basin system.

A Stratigraphic and Sedimentologic Analysis of a Lower Atoka Sandstone, Frontal Ouachita Thrustbelt, Western Arkansas: ABSTRACT

Abstract Prolific lower Atoka (Pennsylvanian) gas reservoirs have been exploited in the frontal Ouachita thrustbelt of eastern Oklahoma. Although the thrustbelt extends into western Arkansas, Pennsylvanian reservoirs have not been recognized. A lower Atoka sandstone unit, exposed behind the Ti Valley thrust fault, exhibits characteristics that indicate favorable reservoir quality. The outcrop is a succession of very fine to medium grained litharenite. Three zones are distinguished by grain size, mineral composition and sedimentary structures. The stratigraphically lowest zone is very fine grained and is composed mostly of monocrystalline quartz with a clay matrix. Sedimentary structures include scours, horizontal burrows and horizontal laminations. Porosity and permeability are nonexistent in this zone. Alternating sets of horizontally laminated fine to medium grained sandstone and bioclastic sandstone characterize the second zone. Secondary porosity has developed due to dissolution of skeletal grains. The stratigraphically highest zone exhibits porosity and permeability comparable to reservoirs within the Arkoma basin. Porosity values range from 6% to 24% with permeability as high as 248 millidarcies. The zone is a massively bedded, fine to medium grained sandstone. Monocrystalline and polycrystalline quartz are the dominant mineral components along with minor amounts of skeletal fragments . Porosity is secondary and has developed where pervasive chlorite grain coatings preclude silica cementation. The primary sedimentary structure is hummocky cross stratification implying deposition on a storm dominated shelf. The outcrop is significant in that it suggests: (1) the Arkoma shelf extended south of the present Ouachita thrustbelt trend and (2) reservoir quality rocks of Atokan age may be present in the subsurface behind the major thrust faults of the trend in western Arkansas.

Enhanced Interpretations of Thermal Maturity Using Rotational Reflectance of Dispersed Vitrinite, Overmature Strata of the Arkoma Basin and Ouachita Thrust Belt: ABSTRACT

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Clay Mineralogy and Illite Crystallinity of the Atoka Formation, Arkoma Basin, and Frontal Ouachita Mountains

AbstractClay mineralogy (including illite crystallinity) was studied in Pennsylvanian synorogenic sediments (Atoka Formation) in the subsurface of the Arkoma Basin and the adjacent Ouachita thrust belt. Vitrinite reflectance values range from ≥0.8% at the surface up to as high as 4.7% Ro at the base of the Atoka Formation. The mineralogy of the <2 µm fraction of the mudrocks is fairly monotonous and composed of illite (<10% interstratified smectite), Fe-chlorite, kaolinite, quartz, and traces of feldspars. Kaolinite is common at shallow levels and “disappears” in most wells at a thermal maturity of 1.9–2.1% Ro, suggesting its possible use as an independent paleothermal indicator in this basin. Illite crystallinity (IC) values are fairly high (0.3–0.5° 2θ) and show little variation throughout the entire maturity range. In addition, no relation was observed between vitrinite reflectance and illite crystallinity, indicating that IC is not a useful paleothermal indicator in these rocks. Illite is almost exclusively of the 2M1 polytype, suggesting a predominantly detrital origin. Incipient metamorphic and low-grade metamorphic mudrocks in the Ouachita thrust belt to the east of the Arkoma Basin are regarded as the source rocks for the clays of the Atoka Formation. Rapid transportation and deposition by turbidity currents probably played a key role in protecting these unweathered micas from pervasive alteration in the terrestrial environment.

Three-Dimensional Geometry and Kinematics of the Gale-Buckeye Thrust System, Ouachita Fold and Thrust Belt, Latimer and Pittsburg Counties, Oklahoma

The Gale-Buckeye thrust system consists of a series of blind thrusts and associated folds near the boundary between the Ouachita fold and thrust belt and the Arkoma basin in Oklahoma. A dense grid of high-resolution seismic reflection data, augmented by data from exploration and production wells, provides a unique opportunity to analyze the three-dimensional geometry and kinematics of these structures in detail. Results from our interpretation provide new insight into the extent, style, and sequence of thrusts within the Gale-Buckeye thrust system, and contrast with previous models for the region. Specifically, we recognize two previously unmapped transverse structures in the Gale-Buckeye thrust system: a sharp, left-stepping zone of oblique ramps, and a tear fault within the Gale thrust sheet. These transverse structures are spatially coincident with similar structural trends in lower Paleozoic strata beneath the thrust system as well as outcropping structural trends on the surface. This interpretation extends thrusts in the Gale-Buckeye system to minimum strike lengths of 7-9 mi (11-15 km) and fault length-to-displacement ratios of about 10:1. Furthermore, interpreted structural relationships suggest that the Gale and Buckeye thrusts formed in a backward-stepping manner, a new interpretation for faults in this system. Measurement of differential transport angles from our interpretations of the Gale-Buckeye thrust system indicates that along-strike displacement variations of the Gale and Buckeye thrusts are consistent with thrusts from other nonmetamorphic fold and thrust belts. Using the differential transport model, we infer that the tear fault in the Gale thrust sheet indicates a region that became segmented to accommodate excessive along-strike differences in displacement. In addition, we use the model to explain errors in previous interpretations of the Gale-Buckeye thrust system that resulted in the drilling of dry holes. Integrating realistic differential transport angles with our interpretations for extent, style, and sequence of thrusting provides new strategies for hydrocarbon exploration hroughout the region.

Structural Styles and Exploration Strategles along the Leading Edge of Fold and Thrust Belts: Examples from the Ouachita Fold and Thrust Belt, Southeast Oklahoma

Structural Styles and Exploration Strategles along the Leading Edge of Fold and Thrust Belts: Examples from the Ouachita Fold and Thrust Belt, Southeast Oklahoma

Megaregional Project Progress Report

When completed, the first data segment will extend from the Arkoma basin of Arkansas to the East Cameron area, offshore Louisiana and will be approximately 500 miles long. The line will cross the Arkoma basin, the Ouachita thrust belt, the State Line graben trend, the North Louisiana salt basin, the Lower Cretaceous shelf edge and complex faults of southwest Louisiana. Additional Megaregional dip and strike lines are planned for the Gulf of Mexico Basin as the project advances.

A Glimpse of Provenance Through the Diagenetic Haze in Smackover Sandstones of the Gulf Coast: ABSTRACT

Late Jurassic Smackover sandstones deposited in the four interior salt basins of the Gulf Coast have been extensively altered, yet their provenance signature has not been grossly modified on QFL and QmFLt plots. Recalculating framework compositions to account for diagenesis suggests that Smackover sandstones were derived from the Ouachita fold and thrust belt and the interior portion of the North American craton. Differences in framework composition between the four basins result from both diagenesis and provenance. Detrital quartz and rock fragments have been lime modified by diagenesis. The south Texas and Mississippi basin sandstones contain more polycrystalline quartz than the other two basins. Rock fragments in the three eastern basins consist primarily of SRFs and low-grade MRFs; south Texas sandstones contain mostly gneiss and schist. Feldspar composition is controlled by the pore fluid chemistry. The South Texas and Mississippi basins contain potassium-rich K-spar whereas the east Texas and Louisiana basins contain mostly albite. A uniform 6% loss (whole rock) of feldspar can be recognized petrographically in all four basins but this loss does not significantly shift the provenance fields on QFL and QmFLt plots. Mississippi basin sandstones plot primarily in the craton interior provenance field supporting derivation of these sandsmore » from the ancestral Mississippi river, East Texas sandstones are also dominated by a cratonic provenance area. Louisiana sandstones plot in the recycled orogen field and were primarily derived from a local source in the Ouachita fold belt. The provenance of south Texas sands was the interior zone of the Ouachitas, as indicated by the presence of high-grade metamorphic rock fragments and Rb-Sr dates of detrital muscovite.« less

Late Mississippian and Pennsylvanian depositional history in the Arkoma basin area, Oklahoma and Arkansas

The Arkoma basin was depositionally part of a broad, stable shelf along a passive continental margin during much of its history. During the Chesterian, Morrowan, and early Atokan, the depositional patterns on the shelf varied greatly, depending on the inconsistent development of carbonate environments and the intermittent introduction of terrigenous elastics (quartz arenites) from the north. Beginning with the middle Atokan, flexural downwarping of the south margin of the shelf was accompanied by down-to-the-south syndepositional normal faults developed sequentially to the north, as a result of continued collapse of the Ouachita trough. Lithic arenites were introduced into this developing trough from the east, apparently derived from a tectonic provenance southeast of the Ouachita trough, on the southwest margin of the Black Warrior basin. Further closure plus rapid deposition resulted in the closing and filling of this incipient foreland basin by the end of deposition of the middle Atoka. With further compressional deformation, the axis of deposition shifted farther northward with the development of a fully formed and continually subsiding foreland basin (beginning in late Atokan). Lithic arenites were transported westward along the axis of the basin (documented in earliest Desmoinesian). In Arkansas some of the early Desmoinesian sediments apparently came from the uplifted Ouachita thrust belt immediately to the south. During the rest of the early Desmoinesian (most of Krebs Group), with the continued subsidence of the foreland basin, extensive deltaic deposits (sublitharenites) were introduced from the north and provided the primary source of sediments to the foreland basin in Oklahoma. They apparently came from the continental interior to the west and north of the Ozark dome. Although there is evidence of a limited source of sediments from the Ouachita fold belt in Arkansas during the deposition of the Hartshorne Sandstone (earliest Desmoinesian), the fold belt to the west in Oklahoma was apparently quiescent and presumably standing at or near sea level throughout the time of deposition of the upper Atoka and the whole of the early Desmoinesian Krebs Group (Hartshorne, McAlester, Savanna, and Boggy Formations). Although added field confirmations are needed, it is concluded that renewed folding and uplift of the Ouachita fold belt following the deposition of the early Desmoinesian Krebs Group involved also the compression and folding of the Arkoma basin. This ended the progressive downwarping of this basin and shifted the depocenter still farther to the northwest. The core area of the Ouachita fold belt was extensively elevated for the first time resulting in the erosion and transportation of chert pebbles and other sediments to the northwest (Thurman Sandstone). Beginning with the middle Desmoinesian, Cabaniss Group deposition was in a narrow successor foreland basin located to the north-west of the Arkoma basin and to the northeast of the Hunton arch. The Ouachita fold belt was the primary source for terrigenous sediments, periodically including chert-pebble conglomerates, to this area throughout the remainder of the Pennsylvanian.

Potential for Subthrust Gas Fields: Results of Recent Deep Drilling in the Ouachitas: ABSTRACT

The Broken Bow anticline, with dip closure of over 170 mi/sup 2/, is the Oklahoma culmination of a long regional trend extending from Arkansas to central Texas. The Standard Oil 1-22 Weyerhaeuser well, drilled to 18,980 ft, is the first crestal well on this feature to rest the subthrust section beneath the Ouachita fold and thrust belt. The wellspudded in and drilled a substantial section of sloates, phyllites, and calcareous quartzites of presumed Ordovician and Cambrian(.) age. The basal Ouachita thrust was penetrated at 11,714 ft, where an interpreted Ordovician Simpson-Arbuckle section was encountered. Reflectance methods using pyrobitumen and visual determination of metamorphic grade indicated the presence of a significant maturity reversal at the thrust boundary. Although economic quantities of hydrocarbons were not found in this well, the following observations may influence future work. (1) A para-autochthonous section of shelf carbonates and sands exists in the subthrust, at least 60 mi from the leading edge of the Ouachita thrust belt. (2) The abundance of pyrobitumen observed in the Simpson section suggests the former presence of significant hydrocarbons. (3) The well encountered good dolomite reservoir at high maturities (R/sub 0/ = 7-8%) that flowed formation water and unexpectedly contained dissolved C/sub more » 1/ to C/sub 3/. These observations suggest that high maturities alone may not be a condemning factor and should be considered in future exploration plays. « less