38th Parallel Lineament Research Articles

Subsurface Geology of the Warfield Structures in Southwestern West Virginia: Implications for Tectonic Deformation and Hydrocarbon Exploration in the Central Appalachian Basin

Data from over 6000 wells and five multichannel reflection seismic lines were used to constrain the subsurface geometry of the Warfield structures in southwestern West Virginia within the central Appalachian basin. Based on their vertical differences in geometry and structural styles, we divided the Warfield structures into shallow (above the Devonian Onondaga Limestone), intermediate (between the Devonian Onondaga Limestone and the Silurian Tuscarora Sandstone), and deep (below the Ordovician Trenton horizon) structural levels. Shallow structures are related to the Alleghanian deformation above the major detachment horizon of the Devonian shales and consist of the Warfield anticline with a 91.5-m closure and southeast-dipping monoclines, which aided the northwest migrati n and entrapment of oil and gas. At the intermediate level, the closure of the Warfield anticline is lost because the Alleghanian deformation is obscured below the major detachment of the Devonian shales, which explains the reduced production from the Devonian and Silurian reservoirs. Deep structures are characterized by an asymmetric half graben within a continental rift system known as the Rome trough, in which a thick sequence of sedimentary rocks exists to provide sources for overlying reservoirs. Although stratigraphic traps may be associated with thickness and facies changes, the deep level is structurally unfavorable for trapping hydrocarbons. Based on changes we found in map trend, we divided the Warfield structures into a middle segment and southern and northern bends. The middl segment is parallel to the New York-Alabama lineament (a northeast-trending magnetic gradient); the southern and the northern bends are linked to the 38th parallel lineament (a west-trending fault system) and the Burning Springs-Mann Mountain lineament (a north-trending magnetic gradient), respectively. We propose a wedge tectonic model to explain (1) northern and southern bends of the Warfield structures and hydrocarbon distribution in the subsurface of southwestern West Virginia; (2) vertical changes in geometry and structural style from the deeply buried half graben to the overlying asymmetric anticline; and (3) geometric and kinematic relationship among the Warfield structures, the 38th parallel, and the Burning Springs-Mann Mountain lineaments.

Effects of Mississippian Tectonic Movement on Sedimentation and Diagenesis of Greenbrier Group in Eastern Appalachian Plateau: ABSTRACT

The Greenbrier Group of eastern West Virginia consists of marine carbonates interbedded and mixed with siliciclastics that were deposited on a shallow shelf in the Late Mississippian. The Denmar Formation is the lowest unit of the Greenbrier Group present in east-central West Virginia, and it represents a shallow tidal-flat and platform sequence deposited by a transgressing sea during the Meramecian. This transgression was followed by a regression with progradation of Taggard Formation terrigenous clastics onto restricted tidal flats during the earliest Chesterian. The Denmar tidal-flat deposits are characterized by pelleted mudstones, limited and depauperate fauna, calcite-filled and dolomite-filled geodes, caliche crusts, fenestral structures, dolomite, burrows, and channel deposits. The platform deposits include more diverse fauna, less micrite, cross-bedded and massive oolitic grainstones, and cross-bedded quartzarenites. Most of the siliciclastics were derived from the north and east of the Appalachian basin. Additional quartz silt, sand, and pebbles were eroded from an uplifted area within the basin and were incorporated into the tidal-flat and platform sediments. This Meramecian tectonic uplift, considered to be part of the 38th parallel lineament, created a subaerial and submarine topographic high that affected sedimentation patterns dur ng the remainder of Greenbrier deposition. Early phreatic cementation occurred along the flank of the uplift in at least two stages. There is evidence of both penecontemporaneous and later replacement dolomite. In certain strata in the western outcrops, hydrocarbons migrated through permeable layers and filled remaining pores. End_of_Article - Last_Page 318------------

Structural Relationships Between Cottage Grove and Shawneetown Fault Systems, Southeastern Illinois, as Inferred from Gravity Data: ABSTRACT

Gravity measurements, extensive field mapping, and drill hole data have been used to determine the structural relations between the Cottage Grove and Shawneetown fault systems of southeastern Illinois. The Cottage Grove structure is an east-west-trending, right-lateral wrench fault which extends across southern Illinois. The Shawneetown fault is the western extension of the Rough Creek fault system of Kentucky and consists of several high-angle reverse and normal faults. Both fault systems are part of Heyl's 38th Parallel lineament; however, the relation between them has been obscured by Pleistocene lacustrine and fluvial sedimentation. Over 400 new gravity stations, with approximate 0.5 km (0.3 mi) spacing, were occupied in eastern Saline and western Gallatin Counties. The data were reduced to the Bouguer values, contoured, and selected profiles were two-dimensionally modeled. The new data, in conjunction with coal mine, drill hole and field mapping data, suggest an eastward extension and bifurcation of the Cottage Grove system. The northern segment continues eastward, dying out just west of the north-south Wabash Valley fault system. The southern segment trends southeastward, possibly merging with the Shawneetown fault system in a complexly faulted zone. The use of gravity data in conjunction with other structural information may provide a useful tool for defining structure obscured by unconsolidated deposits in southern Illinois and other parts of the Illinois basin. End_of_Article - Last_Page 1460------------

Satellite and surface geophysical expression of anomalous crustal structure in Kentucky and Tennessee

An equivalent layer magnetization model obtained from inversion of long-wavelength satellite magnetic anomaly data indicates a very magnetic source region centered in south central Kentucky. The magnetization maximum nearly coincides with a gravity high elongated north-south and extending into Tennessee. Previous refraction profiles suggest that the source of the gravity anomaly is a large mass of rock occupying much of the crustal thickness. The outline of the source delineated by gravity contours is also discernible in aeromagnetic anomaly patterns. Taken together, the geophysical data suggest a large, localized mass of intracrustal rock which is both dense and very magnetic. A simple magnetization/density model is given which accounts for the gravity and long-wavelength aeromagnetic anomalies due to the body. We interpret it as a mafic plutonic complex, and several lines of evidence are consistent with a rift association. The body is, however, clearly related to the inferred position of the Grenville Front. It is bounded on the north by the fault zones of the 38th Parallel Lineament. The inferred mean magnetization (4 A/m) of the body is large, but not inconsistent with values reported by others for deep crustal bodies associated with long-wavelength magnetic anomalies. Such magnetization levels can be achieved with magnetic mineralogies produced by normal oxidation and metamorphic processes and enhanced by viscous build-up, especially in mafic rocks of alkaline character.

Geochemical Survey of Lower Pennsylvanian Corbin Sandstone Outcrop Belt in Eastern Kentucky

Geochemical anomalies that may constitute further evidence for the existence of the east-west trending 38th Parallel lineament have been discovered in Wolfe, Powell, and Menifee Counties, Kentucky. Stream-water, stream-sediment, and outcrop samples collected along the northeast-southwest-trending Corbin Sandstone outcrop belt show anomalous concentrations of U, Th, Zn, Cu, and Ni only in parts of the belt that skirt the 38th Parallel lineament. Landsat studies also show that anomalies are closely associated with the intersections of the four major linear trends present in eastern Kentucky. This association, in part, suggests that the anomalies resulted from ascending fluids which utilize these lineaments as conduits. The presence of slightly uraniferous rock at Bell Branch in Menifee County (together with the presence of geochemical anomalies in the stream-water and sediment samples in Powell, Wolfe, and Menifee Counties) is encouraging even though commercial quantities of uranium or base metals have not been discovered. An anomalously uraniferous kimberlite pipe in Elliot County warrants additional study for this part of eastern Kentucky.

Geophysical Evidence for Deep Basin in Western Kentucky

The Rough Creek fault zone is a major element of the 38th Parallel lineament in western Kentucky and southern Illinois near the head of the Mississippi embayment. Gravity, magnetic, and subsurface data suggest that this fault zone marks the northern boundary of a large graben in the Precambrian basement for which we propose the name Rough Creek graben. This graben is a major structural feature which probably formed initially in late Precambrian to early Paleozoic time and has been reactivated (perhaps several times) during the late Paleozoic and possibly the Mesozoic. The graben is as much as 5.5 km deep and the large volume of deeply buried sediments favors further exploration.

A search for the 38th Parallel Lineament near Green Bank, West Virginia

A field reconnaissance was carried out near Green Bank, West Virginia, to assess the possibility that active faults might produce movements which would introduce errors to geodetic results of Very Long Baseline Interferometry (VLBI) measurements carried out with radio telescopes at the National Radio Astronomy Observatory (NRAO). The 38th parallel lineament, a zone of strike-slip faults and other features, has been proposed by several authors to pass through the Green Bank area and to extend to the Blue Ridge in Virginia. This study, based on Landsat photogeologic mapping, found no evidence for the existence of the lineament in exposed Paleozoic rocks, and a seismometer emplaced at the NRAO detected no activity that could be related to the lineament. It is concluded that the 38th parallel lineament, though well-documented in the midcontinent region, does not extend this far east and that it is probably a purely intracontinental structure unrelated to oceanic fracture zones of the Atlantic.

AGU Midwest Meeting Report

Approximately 150 Midwestern geophysicists attended the third annual AGU Midwest Meeting, which was held at Purdue University, September 26–28, 1977. The majority of the 75 papers presented were related to topical special sessions arranged by seven sections of the Union to be of particular, current importance to Midwestern geophysics. The interest shown in the meeting indicates not only the vigor of current geophysical research in the Midwest but also the desirability of continuing these meetings.The majority of the papers presented were in the area of solid‐earth geophysics, and these primarily were concerned with the paleogeodynamics and contemporary geodynamics of the Midwest. They reflect the growing interest in deciphering the complex evolutionary history of the continental interior by utilizing a wide range of methodologies and the concepts of plate tectonics which have generally emphasized oceanic and continental margin features. The papers in the session on Geology and Geophysics of the Precambrian Basement Rocks of the Midcontinent Region demonstrated that geophysical data can be used to clarify and amplify our understanding of the basement geology in poorly exposed regions. By extension of the data base to include buried portions of the basement, it soon may be possible to determine the major structural, lithologic, and chronologic provinces of the basement in the Midwest fairly accurately. The session dealing with Geodynamics of Plate Interiors demonstrated that the structures present in the midcontinent reflect a long and complex midplate tectonism which is not completely understood. The 15 papers of the sessions on the New Madrid Seismic Zone, the 38th Parallel Lineament, and the Seismicity of the Midwest illustrate the rapidly broadening interest in and knowledge of the tectonic framework of the seismically active New Madrid area and environs. It was emphasized that this area is an excellent example of reactivation of ancient structures during the Phanerozoic and locally into the present. Interpretation of surface, air, and satellite geophysical and geological data suggests the presence of an ancient easterly striking rift south of the 38th Parallel Lineament and a northeast‐trending graben lying along the axis of the New Madrid Seismic Zone. Microearthquakes together with historical seismicity are being used to delineate active faults of this area and estimate earthquake recurrence rates and the local stress state.

Energy Resource Implications of 38th Parallel Lineament across Appalachian Basin: ABSTRACT

Energy Resource Implications of 38th Parallel Lineament across Appalachian Basin: ABSTRACT

Chemical equilibria in the thermal spring waters of Virginia

The composition of waters from 10 thermal springs located in western Virginia near the 38th parallel lineament have been analysed for major dissolved components and for Sr, Fe, Cu, Zn and Cd; from these analyses, free ion activities have been calculated. The temperatures of the springs range from 17° to 39°C, the heat apparently being derived simply from deep circulation along synclinal, Middle Ordovician limestones. More than 95 per cent of the dissolved solids consist of Ca 2+, Mg 2+ HCO 3 −, and SO 4 2−. The concentrations of these components, as well as the spring temperatures, have not changed appreciably in 140 yr in some springs. The waters that have temperatures below 25° are all undersaturated with respect to calcite and dolomite, possibly because they have been contaminated by shallow ground waters. The waters with temperatures above 25° are in equilibrium with calcite and dolomite. Furthermore, in this latter group, the calcium-sulfate activity product and the sulfate-carbonate activity ratio are nearly constant, even though the waters are under saturated with respect to gypsum, anhydrite, celestite and strontianite. This can be explained if CaSO 4 is coprecipitated in a mineral such as aragonite. The waters have absorbed some dissolved oxygen near the surface, but at depth they may be anoxic with Eh controlled by the oxidation of pyrite to goethite. The extremely low chloride concentrations of these waters clearly distinguish them from the brines which deposited Mississippi Valley and Appalachian type epithermal ore deposits.

The 38th Parallel Lineament and Its Relationship to Ore Deposits

Wrench-fault zone, gravity surveys, lead, zinc, barite, fluorite, Northeastern Virginia to South-Central Missouri

Tertiary Felsite Intrusions in the Valley and Ridge Province, Virginia

Porphyritic albite-felsite sills and dikes are exposed in west-central Virginia in Highland County. Two biotite separates have K-Ar ages of 46.9 ± 1.1 and 47.2 ± 1.3 m.y. Seven whole-rock and the two biotite separates were analyzed for Rb, Sr, and Sr isotopic composition. These results indicate that the felsite is 37 ± 3 m.y. old; because of the very low percentage of radiogenic Sr 87 in the whole-rock and biotite samples the Rb-Sr age is considered to be less reliable than the K-Ar age. These results establish a location for Eocene igneous activity in the south-central Appalachian area. The period of time during which igneous activity occurred along the 38th-parallel lineament has been extended considerably. Highland County, Virginia, may have been at least one of the sources of volcanic ash found in sediments from the Coastal Plain of North America. The initial Sr 87 /Sr 86 ratio of 0.704 indicates that the felsite magma was derived from the lower crust or upper mantle.