Ouachita System Research Articles

Organic Geochemistry and Petroleum Distribution on Cherokee Platform, Kansas and Oklahoma: ABSTRACT

In southeastern Kansas and northeastern Oklahoma rocks of the Cherokee Group (Desmoinesian, Middle Pennsylvanian) were deposited across the Cherokee platform--a part of the Mid-Continent craton. These sediments are a clastic sequence of the coal-cycle association. Cyclothems composed of several thin, persistent lithosomes characterize the section. The sedimentary sequence indicates a depositional model of fluctuating conditions which, from a tectono-environmental viewpoint, may be regarded as an unstable dominated by nonmarine and shallow-marine environments (e.g., fluvial, swamp, lagoonal, and littoral). The Cherokee platform is flanked by other Middle Pennsylvanian tectonic features. The mildly positive Ozark dome on the east, the active Nemaha ridge on the west, and the cratonic area on the north affected significantly the depositional history of the platform. The most important influence was the adjacent Arkoma basin on the south. The Arkoma basin was an actively subsiding marginal basin between the craton and the orogenic Ouachita system. Rocks of Desmoinesian age in the Arkoma basin are a clastic wedge whose principal source area was the Ouachita orogenic region. Rapid sedimentation in the Arkoma basin kept pace with subsidence. As a result, the basin floor generally was close to sea level. Hence, most of the clastic wedge consists of coarse terrigenous clastic strata, shal , and coal, and was deposited under nonmarine conditions. Desmoinesian strata of the clastic wedge are partly continuous with Cherokee platform rocks. Much of the detritus deposited on the platform (including carbonaceous matter) was derived from the south and transported across the nonmarine Arkoma basin. Although the strandline fluctuated widely, its average position was near the craton-marginal basin hingeline. Organic geochemical aspects of the Cherokee platform sediments were influenced by the tectono-environmental setting. This influence is displayed by regional contour maps of organic geochemical properties. For example, contour maps of organic carbon, hydrocarbon, and carbon-isotope data display regional variations related to the clastic wedge on the south and more persistent marine depocenters on the shelf. Most regional geochemical variations of the Cherokee section can be related to variations in the proportion of the different rock types making up the section. However, some rock types display smaller but significant regional organic geochemical variations, which also appear to be a response to differences in the tectono-environmental setting across the platform. Perhaps the most imp rtant single aspect that controlled the organic composition of these sediments was the interplay between marine (in situ) and terrestrial (detrital) organic sources. Rate of sedimentation, rate of burial, and postdepositional effects were less important in causing observed variations. The geochemical results support the shelf principle of petroleum origin. Specifically, the regional organic geochemical contour maps suggest a rational explanation End_Page 704------------------------------ for the distribution and compositional variations of the petroleum across the platform. In addition, material balance calculations of oil-in-place versus indigenous sediment hydrocarbons provide a quantitative insight into petroleum migration problems. End_of_Article - Last_Page 705------------

Role of Contemporaneous Faulting During Basinal Subsidence

Faulting contemporaneous with subsidence and deposition is known to characterize various depositional basins. For example, movement along major faults occurred during subsidence of the small but active Los Angeles, Hanna, and Ardmore basins and of large basins such as the Ouachita and Gulf Coast geosynclines. The data from these and other basins indicate that faulting is an important, if not the primary, mechanism of basinal subsidence. During subsidence of the basins studied, faulting proceeded independently of the depositional framework. Major fault movement occurred in the Los Angeles basin during the Mio-Pliocene as turbidites were deposited, in the Hanna basin during the Paleocene-Eocene as alluvial deposits formed, and in the Ardmore basin during the Pennsylvanian as shallow-marine and paralic sediments were deposited. During late Paleozoic time, contemporaneous faulting occurred in the Ouachita system as turbidites and, later, shallow-marine beds were deposited along its length. Subsidence of the Gulf Coast geosyncline is thought to have accompanied the same type of faulting which originates in the basement. There paralic and alluvial sediments overlie offshore or deep-water clay in the overall regressive se uence which formed during the Cenozoic. Another type of faulting, involving only the sedimentary basinal fill, occurred during subsidence of the Gulf Coast geosyncline. Salt and some thick shale units have been deformed by uniform flow which, in turn, apparently caused failure by faulting in the overlying paralic sediments. These sedimentary faults, which do not involve the basement directly, are thought to result from conditions analogous to those which give rise to the Recent mudlumps of the Mississippi delta or the slide-flows experienced in foundation engineering.

Basement Rocks in Continental Interior of United States

Basement Rocks in Continental Interior of United States

Regional Magnetic Map of Florida

A regional magnetic map of Florida reflects the structural trends of the magnetically heterogeneous Paleozoic and Precambrian rocks underlying the coastal plain rocks. Many trends and features on the magnetic map have gravity counterparts, indicating a common source. On the basis of the regional magnetic trends, Florida is divided into two tectonic provinces with an intervening zone of intrusive rocks. Depth estimates from aeromagnetic data suggest the possibility that faulting may be a factor in the profound downwarping and accumulation of sediments in the southern province. The trends of the northern province parallel those of the Appalachian system to which they are probably related. The southern province, distinguished by northwest trends, is structurally discordant w th the northern province. The magnetic evidence suggests that the southern province is a continuation of the Ouachita system which has been traced beneath the Gulf Coastal Plain to within 60 miles of the subsurface extension of the Appalachian system in Mississippi, where the two systems approach each other at nearly a right angle.

Problems of Paleozoic Tectonics in North-Central and Northeastern Mexico: GEOLOGICAL NOTES

Pre-Mesozoic terrane of northern Mexico consists of a granitic area in eastern Coahuila bordered on the W by Pennsylvanian(?) and Permian rocks, on the E by sedimentary rocks of unknown age and on the SE by Mississippian-Permian rocks in fault contact with pre-Mississippian gneiss and schist. The area was a Paleozoic tectonic land. No direct or simple connection with the Ouachita belt of the United States can be implied, but it may be an extension of an interior zone of the Ouachita system. Alternatively, the Mexican Ouachita may have re- sulted from a younger foredeep on its foreland side. The Ouachita peninsula is probably a Paleozoic structural unit. Oil and gas, if present, should occur NW of the Sierra del Cuervo and Placer de Guadalupe exposures, possibly in northeastern Chihuahua.

Tectonic Framework of Southeastern United States

This paper reviews the relations in space and time of the mountain system formed during Paleozoic time which dominates the tectonics of the southeastern states. The most conspicuous representatives of the system are the structures of the Appalachian Highlands, but other structures occur in the Ouachita Mountains and other ranges west of the Mississippi Embayment, and still others are concealed by the post-orogenic deposits of the Atlantic and Gulf Coastal plains. From northwest to southeast, the Appalachian Highlands are divisible into the following. 1. The gently deformed Cumberland and Allegheny plateaus, which constitute a foreland area on the northwest flank of the system. 2. The Valley and Ridge province, made up of more strongly folded and faulted Paleozoic rocks but whose structures are nevertheless marginal to the zones farther southeast. 3. The Blue Ridge province, composed of older Paleozoic and pre-Cambrian rocks, which are not only strongly folded, but are also more or less metamorphosed. 4. A metamorphic and plutonic zone, forming the greater part of the Piedmont province, made up of gneisses and other thoroughly metamorphosed rocks, invaded by granite plutons. This zone is believed to lie along the central axis of the Appalachian system. 5. A belt of less metamorphosed sedimentary and volcanic rocks forming the southeast part of the Piedmont province, and lying southeast of the central axis. In addition to these exposed rocks, unmetamorphosed and little folded sedimentary and volcanic rocks occur still farther southeast, beneath the Mesozoic rocks of Florida. The Appalachian system of the southeastern states has been assumed to have been deformed mostly during the Appalachian revolution, toward the end of Permian and Paleozoic time, but there is evidence of earlier movements during the Paleozoic era, beginning with an orogeny of probable Middle Ordovician age. Late Paleozoic movements may well have been merely the concluding phases of the orogeny. The relations between the Appalachian system and the Ouachita system farther west have long been a puzzle. Further evidence on the problem has been obtained as a result of deep drilling in Mississippi and Alabama, but evidence is as yet insufficient to establish the relation. It is tentatively suggested that the Ouachita system is a westward extension of an interior belt of the Appalachian system, which has been thrust northward to a moderate extent over the westward extension of the belt of the Valley and Ridge province. End_Page 635------------------------------ Fig. 1. Tectonic sketch map of southeastern United States to show mountain systems of Paleozoic time, and their relations to other structural features. End_Page 636------------------------------ Fig. 1. Continued. See caption on page 636. End_Page 637------------------------------

Permo-Carboniferous Orogeny in South-Central United States

This paper is a synopsis of the late Paleozoic orogeny in the south-central states of North America. Recent papers by American geologists and personal work of the writer and his collaborators are coordinated into as complete a treatise as present knowledge permits. Two independent mountain systems, the Wichita and the Ouachita, are distinguished. The Wichita system comprises the Wichita Mountains, the Criner Hills, the Arbuckle Mountains, the buried folds along Red River including the Muenster arch, and the buried Amarillo Mountains. These folds, though belonging to the Permo-Carboniferous phase, originated within an intra-continental pre-Middle Devonian geosyncline, in which the major accumulation of predominantly marine limestone sediments was pre-Devonian. This system strikes generally west and west-northwest. It meets nearly at right angles the front of the second complex, the considerably more important Ouachita system. The Ouachita system (in a wider sense) is a large arcuate feature of which only a small part of the widely overthrust outer rim of the northernmost loop is exposed in the Ouachita Mountains of southeastern Oklahoma and Arkansas. Most of this system is buried, though folds exposed in the Marathon uplift belong to the southwestern extension of the same system, which, as the writer believes, in Oklahoma and Arkansas is itself an extension of the Appalachians, which disappear in Alabama under the Cretaceous blanket of the Gulf Coastal Plain. Unlike the Wichita complex, the Ouachita ranges originate from an inter-continental Carboniferous geosyncline, with major post-Devonian deposition, principally in the latest Mississippian or earliest Pennsylvanian. The facies of the rocks is also intrinsically different. The exposed part consists of great overthrust masses, of a structural type that can best be compared with the northern front of the European Variscan system in France and Belgium. The principal phases of folding in both the Wichita and the Ouachita systems are Pennsylvanian; the final phase of the overthrusting of the Ouachitas is possibly Permian. Precursory Mississippian and older movements are indicated. End_Page 991------------------------------ Recent geological subsurface work makes possible the tracing of the rim of the buried Ouachita front range through east-central Texas, first by the characteristic, depressed early Pennsylvanian foreland basin, which exactly reproduces the coal basin foredeep of southeastern Oklahoma and southern Arkansas, and then by wells which actually have penetrated to the mountain front. The present Llano-Burnet uplift marks the existence of a resistant buttress in the foreland, causing a salient around which the chains turn, to reassume a southwest course in southwestern Texas and northern Mexico; here the folds reappear at Marathon, beyond which they disappear beneath the Cordillera in Mexico. The Hunton arch is another important buttress, causing the uplift of the folded foreland fault-slices of the Arbuckle Mountains. The character of the nappe (overthrust) structure of the Ouachita chains is discussed and compared with the very similar build of European mountain chains. These mountains are not merely the edge of an ancient Llanoria, but a great range of world-wide importance.