Rock magnetism and paleomagnetism of some intrusions from Virginia

Løvlie, Reidar; Opdyke, Neil D.

doi:10.1029/jb079i002p00343

Cited by 26 publications

(7 citation statements)

References 11 publications

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“…17). Magnetostratigraphic data suggest that intrusive bodies associated with this event were emplaccd in probably less than 1 Myr (Lovlie & Opdyke, 1974).…”

Section: Tectonic and Epeirogenic Influences On Topographymentioning

confidence: 87%

Macrogeomorphic evolution of the post‐Triassic Appalachian mountains determined by deconvolution of the offshore basin sedimentary record

1996

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A perplexing macrogeomorphic problem is the persistence of topography in mountain ranges that were initially formed by orogenic events hundreds of millions of years old. In this paper, we deconvolve the post‐Triassic macrogeomorphic history of a portion of one of these ranges, the central and northern Appalachians, using a well‐documented offshore isopach sedimentary record of the US Atlantic margin. Topography is an important signature of tectonic, eustatic and/or geomorphic processes that produces changes in the erodible thickness of the crust (ETC). We define ETC as the total thickness of crust that would have to be consumed by erosion to reduce the mean elevation of a landscape to sea level. We use the term ‘source flux’, designated by ν˙, to describe the rate of change in ETC attributed to deep‐seated geological processes such as crustal thickening, crustal extension, magmatic intrusions or dynamic flow in the mantle. In a mountain belt, the rate of change of mean elevation with respect to a base level, designated by ż′, can be represented as ż′ = c(ν˙ − kd z′ −; ėc ) −& hairsp;l˙, where kd is a proportionality constant relating the mean mechanical erosion rate to mean elevation, ėc is the mean chemcial erosion rate, c is a compensation ratio (held constant for Airy isostasy at 0.21) and l˙ is the rate of eustatic sea‐level change. This equation describes the sum of constructive source terms, two destructive erosion terms and a eustatic sea‐level term. We use this simple linear equation to develop a landscape evolution model based on the concept of a unit response function. The unit response function is analogous to a unit hydrograph which describes the relationship between input (rainfall) and output (discharge) in a hydrological system. In our case, we solve for the general relationship between the source flux into the mountain belt and the erosional flux out of the belt. Offshore sediment volumes are used to determine the erosional flux. Drainage basin area is treated as either a constant (pinned drainage divide) or as increasing through time (migrating drainage divide). We use a third‐order polynomial fit to a global sea‐level curve to account for long‐term eustatically driven changes in ETC and in drainage basin area. Chemical erosion is treated as a constant fixed at 5 m Myr−1. We consider two end‐member models. The first is a ‘tectonic’ model in which the source flux is allowed to vary while kd is assumed to be constant over geological time and equal to its mean Pleistocene value of about 0.07 Myr−1. The second is an ‘erodibility’ model in which kd is allowed to vary, reflecting changes in climatic, climatic variables and rock‐type erodibility, while the source flux is held constant at zero. The ‘tectonic’ model reveals four important increases in the source flux, ranging from 200 to 2000 m Myr−1 that occur over short (<10 Myr) time spans, followed by a protracted period (>25 Myr) where ν˙ drops below zero to values of −1000 to −6000 m Myr−1. The ‘erodibility’ model produces a topography that decays i...

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“…17). Magnetostratigraphic data suggest that intrusive bodies associated with this event were emplaccd in probably less than 1 Myr (Lovlie & Opdyke, 1974).…”

Section: Tectonic and Epeirogenic Influences On Topographymentioning

confidence: 87%

Macrogeomorphic evolution of the post‐Triassic Appalachian mountains determined by deconvolution of the offshore basin sedimentary record

1996

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“…(1) Mooser et al, 1974;(2) Neville, et al, 1979;(3) Souther and Symons, 1974;(4) Bingham and Stone, 1976;(5) Kono etal., 1967;(6) Mankinen, 1972; (7) see 5; (8) McFadden et al, 1979;(9) MaeFadden, 1977;(10) Steele, 1971;(11) Watkins etal., 1971; (12) see 1; (13) Torreson etal., 1949;(14) Symons, i969; (15) see 1; (16) see 1; (17) Watkins and Baski, 1974;(18) Young and Brennan, 1974;(19) Beske etal., 1973;(20) Yorketal., 1971;(21) see 1;(22) Gromm6etal., 1972;(23) Becketal., 1977;(24) Gillilandetal., 1969;(25) Larson and Strangway, 1969;(26) Currie and Larochelle, 1969;(27) Hanna, 1977;(28) (29) Lovlie and Opdyke, 1974;(30) Diehl et al, 1977;(31) Shire and Pruss, 1977;(32) see 30;(33) McMahon and Strangway, 1968;(34) Deutsch etat., 1971;(35) Butler and Taylor, 1978;(36) Jacobsen et al, 1980;(37) Vugteveen, 1981;(38) Hanna, 1967;(39) Shive and Fredichs, 1974;(40) Hanna, 1973;(41) Kilbourne, 1969;(42) Scharon and Hsu, 1969;(43) Larochelle and Black, 1963;(44) Foster and Symons, 1979;…”

Section: Introductionmentioning

confidence: 96%

Apparent polar wander paths carboniferous through cenozoic and the assembly of Gondwana

Irving

1982

Geophysical Surveys

377

193

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Abstract. Directions of magnetization observed from rock-units from a given continental block are conveniently summarized by a path of apparent polar wander (apw) relative to that block. This article documents apw paths for the maj or continental blocks spanning the interval from Late Carboniferous (approximately -300 Ma) to the present. It is shown that by passing moving windowsof 30 or 40 Ma duration over the data an apw path can be obtained with little or no loss of features through smoothing. It also is shown that mean pole positions obtained using Fisher's statistics or by calculating modes do not differ significantly. In the analysis 'poor' results are screened out by applying certain minimum reliability criteria. Unit weight is then given to each of the remaining results. No attempt has been made to weight the results differentially because of the risk of added subjectivity.The paths contain many interesting features. One is an interval of rapid apparent polar motion relative to all major land-masses that occurred sometime in the Late Permian and Triassic. The general form of these motions is roughly established, but their timing and detailed form is poorly known because of inadequacies in the paleomagnetic record. Although it is clear that the motions occurred sometime around the Paleozoic-Mesozoic boundary it is not known whether the motions are or are not contemporaneous from continent to continent.Apw paths are of great importance for many problems in geology and geophysics. As an example, the new paths are applied to the question of how should Gondwana be correctly assembled. The results show that the best available reconstruction is the 1937 assembly of Alex du Toit as quantified by Smith and Hallam, with a minor modification by Barton and Molnar for the fit of Australia and Antarctica. Assemblies, that place Antarctica to the south and wrap the Antarctic Peninsula around the southern Andes, are not supported by the paleomagnetic data. There are, however, several obscurities, which derive, it is argued, from the uncertainties in timing the Late Permian to Triassic transitions alluded to above.

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“…K-Ar and 40Ar/ 39Ar dates (table 1 and fig. 3) and paleomagnetic data (Lovlie and Opdyke, 1974;Ressetar and Martin, 1980) suggest that most of the igneous rocks in this region are Eocene. Geochemical data of dated samples from sites in figure 5 and from table 1 are shown in tables 3 and 4.…”

Section: Eocene Intrusive Igneous Rocksmentioning

confidence: 91%

“…Eocene intrusive igneous rocks of mafic and felsic composition (Fullagar and Bottino, 1969;Hunt, 1974;Lovlie and Opdyke, 1974;Wampler and Dooley, 1975;Ressetar and Martin, 1980) occur in the Valley and Ridge province as dikes, sills, plugs, and diatremes (fig. 5).…”

Section: Eocene Intrusive Igneous Rocksmentioning

confidence: 99%

“…H. Smith, analyst. Six altered and contaminated samples at the end of the table are from indicates Eocene age determined by: A, K-Ar and 40Ar/ 39Ar; B, paleomagnetic data (Lovlie and Opdyke, 1974;Ressetar and Martin, 1980) diatreme breccias are porphyritic basalt with large olivine and augite phenocrysts. The basalts are nepheline normative.…”

Section: Eocene Intrusive Igneous Rocksmentioning

confidence: 99%

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Principal oil and gas plays in the Appalachian Basin (Province 131)

Witt¹

1993

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FIGURES 1,2. Maps showing: 1. The surface extent of the Appalachian basin 12 2. Locations of some structural features and places mentioned in the text 14 3. Generalized geologic map of the Appalachian basin 16 4. Penetration chart showing age and position of source beds, reservoir rocks, and principal oil and gas plays in the Appalachian basin 17 5. Schematic cross section athwart the Appalachian basin 110 6-13. Maps showing: 6. The structure on top of the autochthonous Precambrian basement complex under the Appalachian basin 111 7. Conodont color alteration index isograds in the Appalachian basin 112 8. The Upper Devonian sandstone play 117 9. The Lower Devonian Oriskany play 120 10. The Lower Silurian sandstone play 123 11. The Ordovician carbonate shelf play 127 12. The Upper Cambrian and Lower Ordovician Knox carbonate shelf play 130 13. The Rome trough play 133TABLE 1. The relative stratigraphic position of rock units mentioned in the text 18 Contents III EVOLUTION OF SEDIMENTARY BASINS-APPALACHIAN BASIN Principal Oil and Gas Plays in the Appalachian Basin (Province 131

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Rock magnetism and paleomagnetism of some intrusions from Virginia

Cited by 26 publications

References 11 publications

Macrogeomorphic evolution of the post‐Triassic Appalachian mountains determined by deconvolution of the offshore basin sedimentary record

Macrogeomorphic evolution of the post‐Triassic Appalachian mountains determined by deconvolution of the offshore basin sedimentary record

Apparent polar wander paths carboniferous through cenozoic and the assembly of Gondwana

Principal oil and gas plays in the Appalachian Basin (Province 131)

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