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The east-to-west oriented Arkoma Basin is a peripheral foreland basin or depositional trough that developed during the Carboniferous Period. This formation covers an aerial extent of approximately 33,800 square miles and spans from west-central Arkansas into southeastern Oklahoma (McGilvery, Manger, and Zachry, 2016; Perry, 1995). The Atoka Formation, deposited during the early Pennsylvanian, is the largest Paleozoic formation by aerial extent in the state of Arkansas and is located within and comprises the bulk of Arkoma Basin sediments (McFarland, 2004; Nance, 2018). This formation has been informally divided into three divisions, the lower, middle, and upper, based on their stratigraphic response to differing tectonic processes. A tectonostratigraphic interpretation was made for each division of the Atoka Formation using high resolution cross sections; correlated using well log, seismic, and surface data. Five condensed regional transects were constructed that aided in the development of a cross section "grid" meant to represent the deep marine to shallow marine depositional hinge lines. Each of the three Atoka divisions have a different dominant depositional force. The Lower Atoka deposition was dominated by eustasy, and with sediment supply from the start of Arkoma Basin tectonics, the middle division was dominated by tectonic subsidence and the upper was dominated by sediment supply. The transition between the Atoka divisions and the magnitude of migration between each deep marine hinge line indicates the progradation of the Upper Atoka depositional cycles occurred more rapidly than the retrogradation of the Middle Atoka. The maximum flooding of the formation occurred within the Middle Atoka's uppermost informal member, the Morris Member. The Lower Atoka was deposited on an extensive tectonically stable structural platform, which is supported by no lithostratigraphic transition to deep marine deposits within this project's study area. The deep marine deposition is characterized by shales encapsulating tumultuously distributed and isolated sandstone complexes. These sandstone complexes are not correlated to the shallow marine sandstones by anything but a condensed geologic timeline.
The Arkoma Basin is a Carboniferous peripheral foreland basin creating a structural depression covering an approximate area of 33,800 miles2 that extends through east-central Oklahoma and west-central Arkansas. The entire basin fill includes Pre-Mississippian carbonate shelf deposits, Mississippian marine carbonates and black shales, and Pennsylvanian mixed carbonated/clastic and shore zone/deltaic deposits. The Lower Atoka formation (Pennsylvanian) occurs in outcrop along the southern Boston Mountain Plateau in northern Arkansas and extends into the subsurface of the Arkoma Basin over an area of 2,300 miles2. The Lower Atoka ranges from 600 to 1500 feet in thickness and represents a cyclic succession of stacked shelf to shore zone/deltaic deposits recording a single 3rd order (1-10 m.y.) Vail/Exxon depositional sequence. It was deposited across a broad, tectonically stable platform along the southern margin of Laurasia just before its collision with the Gondwana and the formation of Pangea at the end of the Paleozoic. Tectonic influences meant that it was not a 100% stable platform during the Lower Atoka deposition. This affected the deposition of all the sequences in the Lower Atoka. Topographic relief on preceding deposition also helped create areas of accommodation space filled by offset, compensation bedding. Finally, subsidence on a passive margin has been argued to be up to almost 4 km. This helps explain the "long distance" shoreline shifts and cyclicity in the current time of deposition. This means that these 4th to 5th order cycles (10's to 100's k.y.) may reflect glacio eustacy and sediment supply and can be correlated across the entire area or a very large area. In addition, there appears to be a tectonic over print that influences onlap edges that define northern limits and areas of bypass and nondeposition.
The Arkoma basin is an arcuate Paleozoic structural feature in the Ouachita foreland that extends from central Arkansas and westward into southeastern Oklahoma. The Arkoma shelf lies immediately north of the basin and is comprised of Cambrian to Pennsylvanian age sedimentary rocks. In northwestern Arkansas, the stratigraphic and structural transition from the shelf into the northern portion of the Arkoma basin is poorly defined. Wireline logs were used to construct a series of three north to south cross sections, as well as two along-strike west to east cross sections to examine Morrowan and lower Atokan age strata. In addition to cross sections, isopach and structural contour maps were constructed from wireline log correlation. North to south cross sections display thickening to the south, particularly with sandstone and shale units. West to east cross sections exhibit thickening to the east due to proximity to an eastern terrigenous sediment source. Morrow and lower Atoka strata document the initiation of Arkoma basin subsidence during early Pennsylvanian time and reflect an eastern source of terrigenous sediment to the Arkoma shelf.
Haley Field, Loving County, Texas has produced over 300 bcf of gas from Morrowan and Atokan strata in the Delaware Basin. However, only one in four wells drilled in the field is economic. These reservoirs were deposited in a deep-water setting in a basin undergoing active tectonism in response to the Marathon-Ouachita orogeny. The Central Basin Uplift, the Grisham Anticline, and the Red Hills Arch all altered sediment distribution in the basin. Lower and middle Morrow strata are multiple-source submarine ramp turbidites that flowed from the Northwest Shelf and the Central Basin Uplift. A carbonate shelf edge developed along the Northwest Shelf during the late Morrowan and prograded basinward during the Atokan. Channels cut into the high-relief shelf edge fed sand-rich turbidites deposited on the basin plain. Exploration potential exists in stacked channels, fan lobes and overbank deposits associated with turbidites both in the Morrow and the Atoka.
Arkoma basin is a prolific natural gas basin. The defining feature of this basin is the Atoka Formation that was deposited in the early-middle Pennsylvanian. The Atoka is held equivalent to the tectonic and structural evolution of the basin. This study focuses on one of the many gas fields in the Arkoma Basin in Arkansas to assess the stratigraphic and structural evolution that the strata in this particular field display. Aetna Gas Field extends from T. 8N. R. 27 W to T. 9 N, R. 27 W and T. 8 N, R. 26 W to 8N, R. 27. Geographically, Aetna field covers parts of Franklin, Johnson and Logan counties. It is one of the pioneer gas fields in the Arkoma Basin. First discovery of gas in Aetna Field was made in March 1928. The first three producing wells were completed in the upper Carpenter and middle Alma sands of the middle Atoka Formation. An analysis of structures and stratigraphy of the gas field through well log correlations reveal a combination trap for the gas. Using IHS Petra, stratigraphic correlations were performed on 49 wells in 10 cross sections. The wells selected were sorted by several criteria. Gamma ray logs were given priority. Stratigraphic tops were determined for correlation purposes. The stratigraphic tops were picked and correlated. The middle Atoka Formation was addressed exclusively for the purpose of this study. Structural analysis indicates an arch-and-trough setting that led to gas accumulation in this field. The stratigraphic analysis confirms a thickening to the south following the general southern thickening trend of Atoka Formation in the Arkoma Basin.
An early reviewer of this book stated that he had difficulty assessing its marketability because it "falls between the cracks" of geological literature. We have designed this book to meet a need of modem geology: namely, a single source providing both detailed and synoptic stratigraphy of the various regions of North America, through geological time. Shortly after beginning work on such a book, we realized why it had not yet been written: it required six years of effort, assimilation of an incredible amount of information, and two years' additional work to cut the volume down to publishable size. Further, by the time the final chapter was written, the fIrst few were already out of date. Nevertheless, the book lies in front of you. It is intended to serve several purposes. As a textbook, it will serve the following courses: • Regional stratigraphy • Sedimentary tectonics • Regional tectonics • Advanced historical geology • Survey-level paleontology Obviously, not all portions of the book are relevant to all of the above courses. We assume the reader will retain this book after the particular course is done, and will use it as a reference book. Hopefully, others will obtain the book solely for reference purposes. We believe it will be especially useful for the working geologist or academic geologist seeking generalized and some moderately detailed information about a region or geological time interval which is unfamiliar.