Tertiary Intrusions and Associated Phenomena near the Thirty-Eighth Parallel Fracture Zone in Virginia and West Virginia

Dennison, John M.; Johnson, R. W.

doi:10.1130/0016-7606(1971)82[501:tiaapn]2.0.co;2

Cited by 40 publications

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“…1), the eastward decrease in rank within reference seams may formerly have been even more pronounced and may have been modified by a thermal anomaly in western Virginia and eastern West Virginia. The anomaly extends along the thirty-eighth parallel (Dennison and Johnson, 1971) (Figs. 6 and 7).…”

Section: Isoranks As Expression Of Large-scale Geothermal Heatingmentioning

confidence: 99%

Coalification Patterns of Pennsylvanian Coal Basins of the Eastern United States

Damberger

1974

Geological Society of America Special Papers

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Coalification patterns of Pennsylvanian coal basins in the eastern United States reflect (1) depth of burial during later Pennsylvanian and Permian times, when the main coalification took place; and (2) regional thermal disturbances from Permian to recent times.In most of the eastern United States, rank was determined during the main phase of coalification in Pennsylvanian and Permian times and thus reflects former greatest depths of burial. The general decrease in rank toward the Canadian Shield corresponds well to the general northward thinning of the mantle of sediments over the basement. In the coalification map of a reference seam, basins (for example, Illinois Basin) show up as northward extensions of high-rank areas, and positive structures (for example, Cincinnati Arch, Ozark Uplift) appear as southward protrusions of low-rank areas. The sedimentary column over the reference seam, or its stratigraphic equivalents, was thicker within the basins than over the positive structures.If data on rank are plotted on maps for coal seams lying at or near the surface regardless of their stratigraphic age, the close relation to the large structural units is much less pronounced, and the geologic interpretation of such coalification maps is more difficult.Superimposed upon this broad-scale and rather simple coalification pattern that reflects burial depth are several areas of anomalously high rank that are interpreted as being the result of unusually high heat flow sometime after the main coalification had terminated, probably in connection with deep-seated plutonic activity. These H. H. D a m b e r g e r comprise the Rhode Island Meta-anthracite region, the Pennsylvania Anthracite region extending westward into the area of low-and medium-volatile bituminous coals of Pennsylvania and northern West Virginia, the eastern portion of the Arkoma Basin in Arkansas, and possibly also the southern portion of the Illinois Basin and the area of high-rank bituminous coals in southern West Virginia. In the last two regions, the high rank may be explainable solely by greater former depths of burial. The coalification patterns of all these areas are considered anomalous compared to the patterns of adjacent areas and of other coal basins. Supporting evidence for this interpretation of the coalification pattern is furnished by the presence in the same areas of other manifestations of large-scale regional heating and deep-seated plutonic activity.

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Section: Isoranks As Expression Of Large-scale Geothermal Heatingmentioning

confidence: 99%

Coalification Patterns of Pennsylvanian Coal Basins of the Eastern United States

Damberger

1974

Geological Society of America Special Papers

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“…Drake and Woodward [1963] speculate that a major strike slip fault follows the seamount chain, curves to the west, and passes south of Long Island. Dennis [1956Dennis [ , 1972 In a study of magnetic lineations in the North Atlantic, Pitman and Talwani [1972] concluded that the seamount chain was a major transform fault during the early opening of the North Atlantic in the Mesozoic. Barrett and Keen [1976] find that magnetic anomalies of the Mesozoic M series are offset across the New England seamount chain and that the strike of these anomalies is quite different north and south of the chain.…”

Section: Ottawa-bonnechere Grabenmentioning

confidence: 99%

Intraplate seismicity, reactivation of preexisting zones of weakness, alkaline magmatism, and other tectonism postdating continental fragmentation

Sykes¹

1978

Reviews of Geophysics

670

295

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The distribution of intraplate earthquakes and of igneous rocks postdating continental rifting is summarized and placed into a plate tectonic framework for the following continental areas: eastern and central North America, Africa, Australia, Brazil, Greenland, Antarctica, Norway, Spitsbergen, India, and the margins of the Red Sea and Gulf of Aden. In continents, intraplate earthquakes tend to be concentrated along preexisting zones of weakness within areas affected by the youngest major orogenesis that predates the opening of the present oceans. Many preexisting zones of weakness (including fault zones, suture zones, failed rifts, and other tectonic boundaries), particularly those near continental margins, were reactivated during the early stages of continental separation. In contrast, intraplate shocks rarely occur within the older oceanic lithosphere or within the interiors of ancient cratonic blocks of the continents. In several continental areas, rocks and tectonic features postdating the opening of present‐day oceans, including carbonatites, kimberlites, other alkalic rocks, mafic dikes, and ring dikes, as well as some of the largest intraplate shocks, seem to be located preferentially along old zones of weakness near the ends of major oceanic transform faults that were active in the early opening of adjacent oceans. In several places, alkaline magmatism and earthquakes extend several hundred kilometers inland from the ends of oceanic transform faults (but not necessarily with the same strike as the transform fault). Major preexisting zones of weakness that are oriented subparallel to the directions of relative continental separation appear to control the locations of transform faults that develop in a new ocean. In some instances, alkaline magmatism persisted along reactivated features of this type for as long as 100 m.y. after the initial stages of continental fragmentation. Most kimberlites in South Africa seem to have been emplaced along preexisting zones of weakness that were reactivated during the early opening of the South Atlantic. The type of intraplate magmatism appears to be related to the thickness of the lithosphere. Unlike oceanic transform faults where large horizontal movements have occurred, reactivated zones of weakness in continents usually appear to have been the sites of only relatively small displacement. Seismic activity and alkaline magmatism may be controlled by deep fractures that penetrated the entire lithosphere to tap asthenospheric sources of magma. Seismic activity along these zones seems to occur in response to the present‐day stress regime, which is not necessarily the same as that which was active during the emplacement of the alkaline rocks. Other intraplate shocks are concentrated along old zones of weakness that are subparallel to continental margins. Such shocks are found in the Appalachians, northeastern and northern Greenland, Norway, Great Britain, Spitsbergen, northern Canada, and Australia. These zones of weakness were also reactivated during continental separation...

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“…This is probably a large scale phenomena although a more local cause cannot be ruled out. For example the proximity of the recently active 38th parallel fracture zone (Dennison & Johnson 1971) may be important. Unfortunately, the vertical component at Weston was highly contaminated by temperature fluctuations which could only be partially removed in analysis.…”

Section: Preliminary Interpretationmentioning

confidence: 99%

Magnetotelluric and Magnetovariational Studies in Atlantic Canada

Cochrane

Hyndman

1974

Geophys J Int

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The geographic pattern of the Atlantic Canada coastal geomagnetic induction anomaly is delineated using both the vertical transfer function and the attenuation of the ' normal ' vertical component. Numerical transfer function modelling in the spatial-time domain over the frequency range 5to 120-min period indicates anomalous induction due to the transition from highly conductive deep crust and mantle beneath the Scotian Shelf and Grand Banks to more resistive structures inland. The enhanced deep crustal conductivities may arise from hydration processes associated with long term low grade tectonic subsidence. Additional observations in eastern North America suggest the Atlantic Canada anomaly is related to a large region of high conductivity underlying the seaward side of the Appalachian system.High frequency (< 10-min period) local magnetic induction anomalies adjacent to shallow salt water bodies are quantitatively approximated by Cagniard theory current flow within the water masses. Anomaly intensification by electrical current funnelling is apparent at one station. Telluric fields on land are strongly perturbed by superficial conductivity contrasts making them comparatively less useful than geomagnetic soundings for the study of deep conductivity structure.

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Tertiary Intrusions and Associated Phenomena near the Thirty-Eighth Parallel Fracture Zone in Virginia and West Virginia

Cited by 40 publications

References 0 publications

Coalification Patterns of Pennsylvanian Coal Basins of the Eastern United States

Coalification Patterns of Pennsylvanian Coal Basins of the Eastern United States

Intraplate seismicity, reactivation of preexisting zones of weakness, alkaline magmatism, and other tectonism postdating continental fragmentation

Magnetotelluric and Magnetovariational Studies in Atlantic Canada

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