Ouachita Fold Research Articles

Reservoir systems of the Pennsylvanian lower Atoka Group (Bend Conglomerate), northern Fort Worth Basin, Texas: High-resolution facies distribution, structural controls on sedimentation, and production trends

This study defines the depositional systems of mature lower Atoka Group reservoirs, structural influence on their sedimentation, and sand-transport patterns at a higher degree of resolution and over a significantly larger part of the play area than previously conducted. The reservoir systems are characterized by pronounced variations in depositional style, even between stratigraphically adjacent systems. They represent a variety of on-shelf siliciclastic depositional facies, including gravelly braided river, fluvial-dominated delta, and low-sinuosity incised river deposits. Penecontemporaneous, high-angle, basement-rooted reverse faults and genetically associated folds of the Mineral Wells–Newark East fault system exerted direct control on the orientation of complex fluvial-channel and delta-distributary sand-transport pathways and the geometry of deltaic depocenters. Multiple contemporaneous source areas, including the Ouachita fold belt to the southeast, the Muenster arch to the northeast, and the south flank of the Red River arch, also contributed to the complexity of sandstone trends in the lower Atoka play area. Bubble maps of normalized per-well first-year production and total cumulative production allow qualitative conclusions regarding geologic controls on production distribution. Most wells with optimal gas production occur within two northwest-trending production fairways that coincide with primary sandstone trends of one or more reservoir systems. Highest per-well oil production exists where lower Atoka reservoir facies occur above oil-prone Barnett Shale source rocks (vitrinite reflectance 1.1% Ro) in the western and northwestern parts of the study area. Widespread fault-bounded, karst-produced sag structures that extend vertically from the source rocks through the lower Atoka Group most likely served as hydrocarbon-migration conduits and formed traps for both oil and gas.

Sea level changes and rapid crustal movements in cratonic areas in the Late Paleozoic

In the Phanerozoic, the sea depth in epeiric sedimentary basins showed considerable variations, often accompanied by regression. In periods of regression and erosion, the subaerially exposed shelf and the adjacent parts of the marine basins gave rise to numerous nonstructural (stratigraphic) hydrocarbon traps. Sea depth variations with a magnitude of up to 100–200 m and 1–3 myr long (third-order cycles) are usually attributed to the eustatic fluctuations of the sea level. To estimate their possible range, a model is proposed which describes the water depth variations as a function of eustatic fluctuations in tectonically subsiding carbonate platforms. We take into account the crustal isostatic response to the changing water load and the finite time necessary for soil and karst formation in the exposed shelf or its upper part. This model allowed analyzing data on the reference sections of the North Timan shallow-water sediments. According to the analysis, the third-order sea level changes in the Middle Carboniferous, Late Carboniferous, and Early Permian did not exceed several tens of meters. During the same period, shorter fluctuations (∼100 kyr) occurred owing to the waxing and waning of large Gondwanan ice sheets. In the first half of the Bashkirian Age (Early Pennsylvanian), regression took place in the East European and North American cratons and then shallow-water sedimentation resumed. This regression is usually attributed to a considerable sea level fall. In some other areas, slow shallow-water sedimentation continued throughout the Bashkirian. This suggests that the Bashkirian regression was due to the crustal uplifts. Short-term uplifts can be explained by ascending convective currents beneath the asthenosphere. In southern North America, they brought an active fluid into the lithosphere. This caused rapid eclogitization-related crustal subsidence in the Arkoma and Anadarko basins as well as intense lithospheric weakening and shortening in the Ouachita Fold Belt.

Gravity constraints on lithosphere flexure and the structure of the late Paleozoic Ouachita orogen in Arkansas and Oklahoma, south central North America

Spectral analysis of Bouguer gravity anomalies in western central Arkansas and eastern Oklahoma indicates that the thickness of the crust in the Ouachita fold and thrust belt increases from 38 km in the western Ouachitas to 44 km in the eastern Ouachitas. The change in crustal thickness occurs near the western end of the Broken Bow uplift and coincides with an abrupt decrease in the flexural rigidity of the lithosphere from 1.8×1024 N m in the western Ouachitas to 5.0×1023 N m in the eastern Ouachitas. The flexural rigidity in the western Ouachitas is similar to values determined in the Appalachian fold and thrust belt and coincides with the depth of the 450°C isotherm predicted by conductive cooling models for the thermal evolution of the early Paleozoic southern Laurentian rifted continental margin. The thick crust in the eastern Ouachitas results in lithosphere that is anomalously weak for rifted continental crust of this age. The thicker crust is attributed to an eastward transition from a rift segment to a transform segment of the Paleozoic continental margin. A layered density model derived from the gravity data shows that strata interpreted to be deformed Ouachita facies rocks are thickest in the eastern Ouachitas and are consistent with a greater amount of shortening in the central thrust belt in Arkansas as compared to Oklahoma. The opposite relationship is observed in the frontal Ouachita province, where shortening appears greater in Oklahoma. The cross‐strike changes in the locus of shortening, crustal thickness, flexural rigidity, and the inferred transition from rift to transform segments of the early Paleozoic continental margin all coincide with the location of a previously hypothesized zone of diffuse rightlateral shear located at the western end of the Benton uplift. Flexural modeling indicates that the load required to produce the observed Bouguer gravity low in the Arkoma foreland basin trends parallel to the Benton and Broken Bow uplifts but is located 114 to 276 km farther south. In the western Ouachitas, the position of the load coincides with the northern edge of the Sabine uplift and is interpreted to mark the southern extent of Ouachita facies rocks that were emplaced on the Laurentian continental margin and/or attached remnant oceanic crust.

Comparison of the Ouachita and Carpathian Fold Belts  :ABSTRACT

Comparison of the Ouachita and Carpathian Fold Belts  :ABSTRACT

Geometry of Thrusting in the Wilburton Gas Field and Surrounding Areas, Arkoma Basin, Oklahoma: Implications for Gas Exploration in the Spiro Sandstone Reservoirs: ABSTRACT

Abstract The Arkoma basin is an arcuate structural feature located in southern Oklahoma and western Arkansas. It is recognized as a foreland basin of the Ouachita fold and thrust belt and is one of the most prolific gas producing basins in North America. The Choctaw fault is the leading-edge thrust of the Ouachita frontal belt. Several south-dipping leading imbricate fan thrust faults are present in the hanging wall block of the Choctaw. The Wilburton gas field is located in the central part of the basin and produces mostly from the Pennsylvanian (Atokan) Spiro Sandstone. We have constructed many balanced structural cross sections in the Wilburton gas field and adjacent areas to determine the detailed geometry and structural history of the thrusting. The cross sections are perpendicular to the tectonic transport direction and are based on updated surface geology by the Oklahoma Geological Survey, wire-line well log data, and our interpretation of several seismic profiles donated by the EXXON oil company. The restored cross sections suggest about 40% shortening in the Wilburton gas field area. There is a good correlation between the presence of Chamosite clay and the porosity and permeability in the Spiro Sandstone. The original distribution of the Chamosite bearing facies in the Spiro sandstone was plotted on the cross sections to determine the extent of potential reservoir rock. In the Wilburton area, the cross sections suggest a shallow triangle zone floored by the Lower Atokan detachment and flanked by the south-dipping Choctaw thrust to the south and north-dipping Carbon fault to the north. The foot wall of the Choctaw contains duplexes that are located between Springer detachment (the lower detachment) and the Lower Atokan Detachment (the upper detachment). These duplexes contain overpressured Spiro sandstone gas reservoirs. There is a rough correlation between the pressure data in the Spiro reservoirs and the duplex structures. The highest pressure-depth gradients are found in the Spiro reservoirs that were brought to structurally higher positions by the thrust faults in the duplex structures. Structurally lower reservoirs exhibit lower pressure-depth gradients. Therefore, we suggest that the thrusting in the duplex structures may have formed seals that isolated the Spiro Sandstone gas reservoirs.

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.

Ouachita-Appalachian Juncture: a Paleozoic Transpressional Zone in the Southeastern U.S.A.

The northern margin of Gondwana collided with the southern margin of the North American craton in the late Paleozoic (330-265 Ma). Near-normal compressional stresses, generated where the trend of the North American margin was nearly perpendicular to Gondwana's plate-motion vector (closure direction), caused extensive crustal shortening and decollement thrusting within the sedimentary section. The Appalachian and Ouachita fold belts are the erosional remnants of this collision on the North American margin. Transecting the Ouachita fold belt are several zones of late Paleozoic transcurrent faulting: the Val Verde, Ardmore-Anadarko, and Reelfoot zones. They occur where the precollision margin of the North American craton was oriented oblique or parallel to the closure direct on with Gondwana. Stresses generated within these zones during the collision were transpressional rather than simply compressional, and gave rise to high-angle faulting, high-amplitude vertical displacements, and the emplacement of positive flower structures. In the Val Verde and Ardmore-Anadarko basins, these features have proven to be major structural traps for oil and gas. On the basis of seismic and well data, this study identifies a zone of complex structures, including positive flower structures, in the subsurface Paleozoic section of Kemper County in east-central Mississippi. The region is considered to be another transpressional zone analogous to the Val Verde, Ardmore-Anadarko, and Reelfoot zones. The Kemper County zone separates and truncates the Appalachian Valley and Ridge fo d belt in the subsurface from the Mississippi Ouachita deformed belt to the west and is, therefore, also identified as the juncture between the Ouachita and Appalachian fold-belt systems in the southeastern U.S.A.

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

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

Middle Pennsylvanian recurrent uplift of the, Ouachita fold belt and basin subsidence in, the Arkoma basin, Oklahoma

Recurrent uplift of the Ouachita fold belt in Oklahoma coincided with the disruption of the Arkoma basin following the deposition of the Boggy Formation (early Desmoinesian time). The Boggy, composed of sandstone-shale sequences that record southerly progradation of coal-bearing, fluvially dominated deltaic complexes into the Arkoma basin, was folded at the time of uplift of the Ouachita fold belt. The uplift ended the progressive subsidence of the Arkoma basin and shifted the depocenter to the northwest. Subsequently, the Thurman Formation (middle Desmoinesian), which had a source in the southeast, was deposited in the smaller resurgent foreland basin over the folded and eroded surface of the Boggy. Chert-pebble conglomerates in the Thurman were derived from the erosion of newly elevated Ordovician and Devonian cherts in the core of the Ouachita foldbelt. Sandstone-shale packages are found in both formations. The origin of the coal-bearing cycles in the Boggy are enigmatic, but they probably were controlled by a combination of factors such as glacio-eustatic changes in sea level and delta-lobe abandonment. In contrast, cycles in the Thurman probably were strongly influenced by episodic thrust faulting and uplift in the Ouachitas.

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

Possible Future Petroleum Provinces of United States Western Gulf Basin--Pre-Jurassic: ABSTRACT

In the western Gulf basin, the pre-Jurassic section can be subdivided into (1) foreland Paleozoic strata (Black Warrior basin), (2) orogenic geosynclinal facies (Ouachita tectonic belt), (3) late-orogenic, late Paleozoic rocks, and (4) post-orogenic, Late Triassic strata. A good potential for future petroleum provinces of economic interest can be recognized in the Black Warrior basin, and on the Gulf of Mexico side of the Ouachita tectonic belt, in late-orogenic, late Paleozoic strata. A remote possibility is recognized for the presence of commercial accumulations of hydrocarbon in sub-thrust lower Paleozoic foreland carbonates beneath the interior part of the Ouachita fold belt. The hydrocarbon potential of geosynclinal sediments of the Ouachita tectonic belt, and of the post-orogenic Triassic section, is considered to be negligible. The Black Warrior basin of Mississippi and Alabama contains a thick section of Paleozoic foreland rock. Although production dates back to 1909 and hydrocarbon shows have been numerous, the proved reserves are insignificant. The deep structural configuration has been difficult to map, and this has deterred deep drilling. The basin tectonics should be comparable to those of other foreland basins, in which large, buried, normal faults are characteristic. Improved seismic techniques should reveal similar anomalies in the Black Warrior basin. Large hydrocarbon accumulations may ultimately be found in deep fault traps in lower Paleozoic carbonates, and such prospects are sparsely tested. There is no production from pre-Jurassic rocks gulfward from the Ouachita front. However, exploration of this section has been quite limited, mainly because of the absence of attractive objectives. Most wells drilled below the Jurassic have found either tight, highly deformed, geosynclinal facies of the Paleozoic Ouachita system, or redbeds and igneous rocks of the Late Triassic Eagle Mills Formation. Since 1960 a few highly significant, but unpublicized, wildcats have penetrated relatively undeformed, very fossiliferous, shallow-water shelf carbonates and clastics of Pennsylvanian age beneath the coastal plain. These strata, identified from fusulinids as Desmoinesian, are present on the Gulf of Mexico side of the Ouachita fold belt in wells drilled in northeast Texas and southwest Arkansas. Commercial porosities have been found in both sandstones and carbonates. Only fragmentary data are available, but the mere presence of these strata suggests that a potentially large, virtually unexplored, petroleum province may be present in late Paleozoic rocks of the Gulf coastal plain. End_Page 1792------------------------------ A recent 20,000-ft test in Texas penetrated thick lower Paleozoic shelf carbonates on a large seismic anomaly beneath the interior zone of the Ouachita system. Although the objective carbonates were metamorphosed there, the possibility of finding favorable reservoir rock elsewhere in this trend is not necessarily eliminated. End_of_Article - Last_Page 1793------------

Dispersal and Petrology of Sandstones of Stanley-Jackfork Boundary, Ouachita Fold Belt, Arkansas and Oklahoma

Sandstones of the uppermost Stanley and lowermost Jackfork Groups (both flysch deposits) include arkose, subarkose, subgraywacke, feldspathic subgraywacke, and orthoquartzite (Folk, 1954, sandstone classification). Regional study of the uppermost part of the Stanley Group (Moyers Formation) shows that arkose and subarkose occur in the western Ouachita Mountains, and arkose and feldspathic subgraywacke occur in the south-central Ouachitas. Orthoquartzites occur only in the northeastern part of the fold belt. In the lowermost part of the Jackfork Group (Wildhorse Mountain Formation), subarkose occurs in the southern part of the Ouachita geosyncline, whereas subgraywacke is limited to the northwestern part of the geosyncline. Orthoquartzite occurs throughout the rest of the uachita fold belt. A linear regression analysis comparing feldspar content with both clay matrix and authigenic mica indicated that the amount of diagenetic matrix is negligible. Most of the authigenic mica appears to be recrystallized primary matrix. Geographic distribution of sandstone classes suggests that the Moyers Formation was derived from two sources. Quartzose material was derived from a northern source (Ozarks) and feldspathic material was derived from a southern source. Detritus was transported laterally into the Ouachita geosyncline. The sandstone of the Wildhorse Mountain Formation was derived from the same two sources and from a third source east of the present outcrop belt. Quartzose sandstone appears to have been deposited by a combination of lateral supply from the Ozarks and Illinois basin and subsequent redistribution by axial currents. Lateral supply was accomplished by turbidity currents, sand flow, and submarine slumping. Directional mapping of flute casts by others indicated that deposition of sand in the Ouachita geosyncline was accomplished by axially oriented currents rather than by downslope currents. The assumption that axially oriented flute casts were formed by the same turbidity currents that transported sand from the geosynclinal margin is inconsistent with interpretations based on mineralogical data. Oceanographic studies show that deep-water currents, flowing parallel with topographic strike, flow at velocities sufficiently high to erode silt and clay. Similar ocean currents probably reworked the marginally supplied sands and resedimented them in an axial direction in the Ouachita geosyncline. The axial orientation of some sole marks in ancient flysch deposits possibly records the direction of flow of ancient resedimenting ocean currents, whereas the regional distribution of sandstone types possibly indicates lateral supplying of sand by gravity-induced turbidity currents, submarine slumps, or sand flow. An oceanographic model consisting of sand emplacement by gravity-induced processes and later resedimentation by axially oriented ocean currents is offered as the most plausible mechanism to resolve anomalous provenance interpretations based on mineralogical and directional data.