Étude paléomagnétique des roches protérozoïques de la formation de Sakami, région de la Grande Rivière, Territoire du Nouveau-Québec, Canada

1981 ◽  
Vol 18 (12) ◽  
pp. 1893-1899
Author(s):  
Maurice K. Seguin ◽  
Kamal N. M. Sharma ◽  
Gérard Woussen
Keyword(s):  
Magnetic Memory ◽  
Thermal Demagnetization ◽  
Paleomagnetic Study ◽  
Geological Formation ◽  
The Mean

We describe a paleomagnetic study of Mid-Proterozoic sandstone of the Sakami Formation. The thermal demagnetization is more effective than by alternating field; this indicates that part of the magnetic memory is located in hematite. The mean direction of magnetization after thermal and alternating field treatments is 031, −25 α95 = 7.1°, K = 73 and the corresponding paleopole position is 103°W, 18°S (dm = 11°, dp = 8°). These results are important because a part of this geological formation will be covered with water after completion of the development works of La Grande Rivière. [Journal Translation]

Reconnaissance paleomagnetic study of igneous rocks from the eastern sector of the Labrador Trough

1985 ◽  
Vol 22 (11) ◽  
pp. 1561-1570
Author(s):  
Maurice K.-Seguin ◽  
Thomas Clark
Keyword(s):  
North America ◽  
Igneous Rocks ◽  
Polar Wander ◽  
Thermal Demagnetization ◽  
Eastern Sector ◽  
Paleomagnetic Study ◽  
Component C ◽  
The Mean ◽  
Three Components

A paleomagnetic study has been carried out on 75 samples of metagabbro and metaperidotite from 14 sites in the Labrador Trough. The sites were distributed over a distance of 500 km and are situated in sills intruded into formation near the top of the trough stratigraphic column. Four components (A, B, C, and D) were obtained after alternating field (AF) and thermal demagnetization. The mean directions of magnetization are A. 143°, +33°. α95 = 14.4°. k = 15.4, 8 sites: B, 69°, +51°, α95 = 10.3d, k = 22.9, 10 sites: C. 278°. +15°, α95 = 7.7°, k = 28, 14 sites; and D, 200°, +16°. α95 = 13.3°, k = 16.2, 9 sites. All components are secondary. The fold test is negative, and consequently no primary magnetization has been preserved in the isolated components. Component C may have erased all others in zones of highest metamorphism. The paleopoles obtained for components D, A, and C are, respectively, 270°E. 23°S (δP = 10°. δm = 18°); 327°E, 9°S (δp = 11°. δm = 20°); and I9°E, 11°S (antipole) (δp = 10°. δm = 17°). The paleopole positions obtained for these three components are compared with me existing late Aphebian and early Paleohelikian apparent polar wander (APW) path for North America and fall in the 1750–1850 Ma interval.

Paleomagnetic Study and Chemistry of Newer Dolerites from Singhbhum, Bihar, India

1974 ◽  
Vol 11 (8) ◽  
pp. 1043-1054 ◽  
Author(s):  
R. K. Verma ◽  
S. N. Prasad
Keyword(s):  
Free Space ◽  
Regional Metamorphism ◽  
Magnetic Mineral ◽  
Polished Section ◽  
Thermal Demagnetization ◽  
Paleomagnetic Study ◽  
Younger Age ◽  
Igneous Activity

Results of paleomagnetic studies on seventeen dikes sampled from the Newer Dolerites of Singhbhum, between latitude 22°0′N to 22°45′N and longitude 85°48′E to 86°25′E are reported. The dikes are of Precambrian age, probably older than 1000 my. Stable directions of magnetization were obtained for eleven sites by thermal demagnetization in a field free space in temperatures ranging from 250° to 400 °C. These studies showed that the dikes had been reheated by igneous activity of neighboring dikes of a younger age or by regional metamorphism of a younger period. Polished section studies carried out on these dikes showed that the magnetic mineral had been significantly altered as a result of these processes. Reliable virtual geomagnetic poles were obtained for ten different sites. These pole positions can be collected into three different groups which may represent three episodes of igneous activity of the Newer Dolerites. A very tentative polar wandering curve for the Precambrian in India is given.

scholarly journals Paleomagnetism and cycle stratigraphy of the Triassic Fleming Fjord and Gipsdalen Formations of East Greenland

1996 ◽  
Vol 42 ◽  
pp. 121-136
Author(s):  
D.V. Kent ◽  
L.B. Clemmensen
Keyword(s):  
Late Triassic ◽  
Eastern North America ◽  
Stability Characteristic ◽  
East Greenland ◽  
Paleomagnetic Study ◽  
The Mean ◽  
Reversed Polarity ◽  
Formation Section ◽  
Milankovitch Orbital ◽  
Newark Basin

A 210 m section of Late Triassic Fleming Fjord Formation (the Malmros Klint Member and the lowermost 80m of the overlying Carlsberg Fjord beds of the Ørsted Dal Member) in the Tait Bjerg area of the Jameson Land Basin, East Greenland, was sampled for paleomagnetic study and measured for cycle stratigraphie analysis. Paleomagnetic samples were also taken from the underlying Gipsdalen Formation in the Gipsdalen area. A high stability characteristic magnetization carried by hematite was successfully isolated in 63 sampling levels in the Fleming Fjord Formation and 9 sampling sites in the Gipsdalen Formation using progressive thermal demagnetization. The mean characteristic directions for the Herning Fjord and the Gipsdalen Formations may be be biased by sedimentary inclination error but are consistent with a northward drift of East Greenland of about 10° from the arid (ca. 25° N) to semihumid (ca. 35° N) paleoclimatic belts in the Middle to Late Triassic. Seven normal and reversed polarity intervals are clearly delineated in the Fleming Fjord Formation section. A preferred correlation of the magnetostratigraphy to a cyclostratigraphically calibrated reference polarity sequence recently derived from drill cores in the Newark Basin of eastern North America suggests that the sampled interval represents about a 3.5 m.y. interval of the late Norian. The Malmros Klint Member and the overlying Carlsberg Fjord beds have composite sedimentary cycles that vary in thickness from 25 m to about 1 m and seem to match Milankovitch orbital climatic cyclicity with periods of ~400ky, ~100ky, ~40ky, and ~20ky. The composition and thickness ratio of the cycles suggest that the measured section of the Malmros Klint Member and the Carlsberg Fjord beds represents lacustrine accumulation over about 4 m.y., a duration consistent with the magnetostratigraphic correlations.

scholarly journals Paleomagnetism of Siluro-Devonian rocks from eastern Maine

1980 ◽  
Vol 17 (12) ◽  
pp. 1653-1665 ◽  
Author(s):  
Dennis V. Kent ◽  
Neil D. Opdyke
Keyword(s):  
Reasonable Agreement ◽  
Lower Devonian ◽  
Northeastern North America ◽  
Rock Types ◽  
Magnetic Carriers ◽  
Paleomagnetic Study ◽  
Intrusive Rocks ◽  
The Mean ◽  
Upper Silurian ◽  
Accurate Record

A diverse suite of rocks was collected for paleomagnetic study from two formations in the Eastport area of northeastern Maine: 18 sites (103 samples) from redbeds and diabase sills of the Hersey Formation (uppermost Silurian to Lower Devonian) and 14 sites (74 samples) from lavas, redbeds, and calcareous nodules of the Eastport Formation (Lower Devonian; Rb/Sr age 412 Ma). Characteristic magnetizations based on AF and thermal demagnetization analyses give mean directions, after simple correction for bedding tilt, of D = 163.6°, I = 41.3°, α95 = 6.3°, for N = 16 sites in the Hersey, and D = 179.3°, I = 38.0°, α95 = 9.4°, for N = 14 sites in the Eastport Formation. Baked contact relations, the presence of opposite polarities, and the similarity in directions over different rock types and magnetic carriers point to an acquisition of magnetization near to the time of rock formation. The mean directions correspond to (south) paleopole positions at 19.8°S lat., 308.8°E long. (δp, δm = 4.7°, 7.7°) for the Hersey and 23.7°S lat., 293.7°E long. (δp, δm = 6.6°, 11.1°) for the Eastport Formation.These paleopoles are removed from the Upper Silurian Bloomsburg Formation pole, but are in reasonable agreement with similar age results from central Newfoundland, suggesting that the Acadia displaced terrain encompassed these areas. Siluro-Devonian paleopoles from intrusive rocks in northeastern North America are generally widely divergent and these may not be providing an accurate record of paleomagnetic field in all cases.

The Paleomagnetism of Diabase Dikes from the Grenville Province

1971 ◽  
Vol 8 (7) ◽  
pp. 802-812 ◽  
Author(s):  
G. S. Murthy
Keyword(s):  
Primary Component ◽  
Low Temperature Oxidation ◽  
Grenville Province ◽  
Temperature Oxidation ◽  
Dike Swarm ◽  
Grenville Orogeny ◽  
Paleomagnetic Pole ◽  
Paleomagnetic Study ◽  
The Mean ◽  
Magnetic Stability

A paleomagnetic study was attempted of the diabase dike swarm intruding the Grenville structural province of the Canadian Shield. Both the alternating field and thermal demagnetization studies indicated that the dikes have varying degrees of stability of magnetization. Some dikes were shown to have stable primary component of magnetization. Microscopic observations indicated that, in most cases, the primary magnetic mineral titanomagnetite was altered to titanomaghemite, probably due to low temperature oxidation. A good correlation is obtained between magnetic stability and relative abundance of titanomagnetite to titanomaghemite in that dike. The mean paleomagnetic pole for the Grenville dike swarm, which is probably of late Precambrian age, was computed to lie at 3.0° N, 29.0° W with A25 = 11.0°. Comparison of this result with other Precambrian pole positions of similar age relative to North America suggests that the dikes were intruded after the Grenville orogeny.

On the temperature of the springs, wells and rivers of India and Egypt, and of the sea and table lands within the tropics; with a few remarks on M. Boussingault's mode of ascertaining the mean temperature of equinoctial regions

1851 ◽  
Vol 5 ◽  
pp. 502-503
Keyword(s):  
Pure Water ◽  
Diurnal Fluctuation ◽  
Small Surface ◽  
Muddy Water ◽  
Mean Temperature ◽  
Deep Wells ◽  
Geological Formation ◽  
Higher Temperature ◽  
The Mean ◽  
The Tropics

The author adverts to the deficiency of information which has hitherto existed as to the temperature and chemical composition of the springs and rivers both of India and of Egypt; and also as to their geographical and geological relations. He gives, in the present paper, the details of a great number of observations which he has made on these subjects, and which he thinks may prove a useful contribution to Indian hydrography, as well as afford more exact data for philosophical inquiry. The observations extend, at irregular intervals, from Alexandria to Malacca, or from 31º13' of northern latitude to within 2º14' of the Equator, and between the meridians of 27º and 103º of east longitude. In the columns of the register, the date of the observation, the latitude, longitude, approximate height above the sea, nature of the surrounding geological formation, depth to the surface of the water, depth of the water itself, temperature of the air, and approximate annual mean of the climate in which the wells, &c. occur, are, as far as practicable, specified. A column of remarks is added, containing observations on the chemical nature of the water, and on the size of the wells and springs, and the result obtained by other observers. It was found, in general, that in low latitudes the temperature of the deepest wells and springs is a little higher than the mean temperature of the air; although there occur a few exceptions, especially in the neighbourhood of a high range of hills, whence there probably arise cold springs, having their source at an elevation considerably above that of the plain where the water makes its appearance. Springs which are strongly saline and sulphureous, have, on the average, a higher temperature than those of pure water. Both saline and cold springs are found occurring within a few feet from thermal and freshwater springs: a fact which the author is disposed to ascribe to their rising through different seams of the subjacent strata, often much inclined; and to the different depths and heights, above and below the crust of the earth, from which the supply of water is derived. Wells, and particularly those having a small surface, which are much used for purposes of irrigation, thereby acquire an artificial increase of temperature. The temperature of shallow exposed wells, springs and rivers, especially those which have sandy beds, is subject to diurnal fluctuation from the more powerful influence of the atmosphere: and the surface water of deep wells partakes of these vicissitudes to a depth varying according to the transparency of the water, the extent of surface, degree of exposure and clearness of the sky. In muddy water, the surface is heated to a greater extent; but at the depth of a foot or two, it is less affected by the heat of the solar rays than clear water.

The petrology, geochemistry, and remanent magnetization of metabasalts and metagabbros in the Lac Patu – Fort McKenzie region, New Quebec Territory

1976 ◽  
Vol 13 (6) ◽  
pp. 838-846 ◽  
Author(s):  
Maurice K.-Seguin
Keyword(s):  
Remanent Magnetization ◽  
Pole Position ◽  
Magnetic Memory ◽  
Paleomagnetic Pole ◽  
Lower Proterozoic ◽  
Pertinent Information ◽  
The Mean ◽  
The Stability ◽  
Anhysteretic Magnetization ◽  
Chemical Description

One hundred and five specimens were collected from 40 different sites in northwest-striking metabasalts and metagabbros of Lower Proterozoic (Aphebian) age in the northeastern part of the Labrador Trough (longitude: 69 °W, latitude: 57 °N). The radiogenic age determinations of surrounding rocks of the same age yielded 1860 m.y. A petrological and chemical description of the rocks is included. The chemical results for total Fe, MgO, and Na2O + K2O combined, drawn on a ternary diagram show that the metabasalts and metagabbros fall in the tholeiite field. Magnetite (with some occasional 5% ulvospinel) is the most frequent magnetic memory carrier; pyrrhotite is less commonly found. In order to obtain some pertinent information relative to the stability of the NRM component, step-wise alternating field demagnetization was conducted on 40% of the specimens and the others were demagnetized at a specific AF intensity. In 35% of the specimens, the AF demagnetization process induced an anhysteretic magnetization component above 250 Oe. A secondary isothermal remanent magnetization of lesser stability was often detected in the 50–150 Oe range. Tilting of the formations sometimes increased and sometimes decreased the dispersion of the NRM vectors. After tilting the lithological units that were AF demagnetized, the mean paleomagnetic pole position is 152 °E, 20° S (dm = 14°,dp = 07°, K = 34), with at least one reversal.

Study on Tensile Magnetic Memory Characteristics of Demagnetization 16Mn and Q235 Steel

2011 ◽  
Vol 314-316 ◽  
pp. 1079-1082 ◽  
Author(s):  
Feng Yun Yu
Keyword(s):  
Magnetic Field ◽  
Field Intensity ◽  
Inflection Point ◽  
Magnetic Field Intensity ◽  
Magnetic Memory ◽  
Measuring Point ◽  
Q235 Steel ◽  
Deformation Stage ◽  
The Mean ◽  
Memory Characteristics

Tensile tests were carried out on demagnetization 16Mn and Q235 steel samples at loading state, and the magnetic memory characteristics were analyzed. Experimental results show the mean magnetic field intensity (MMFI) of a measuring point is more effective than that of other measuring points at the same stage to study tensile magnetic memory characteristics of demagnetization 16Mn and Q235 steel samples. At the elastic deformation stage, the MMFI of the measuring points at one fracture side increases while it decreases on the other fracture side. The MMFI decreases with the distance from the fracture location, and the change rate of the MMFI is almost equal. The variation law shows changes of opposite direction. At the strengthening phase, the relation between MMFI and tensile displacement is similar with that of the plastic deformation stage, but the variation amplitude was accelerated obviously. Comparison of 16Mn and Q235 steel shows that the standard deviation variation of the magnetic field intensity with the tensile displacement increases as the tensile strength of materials increases. For the demagnetization bearing components, weak areas can be estimated according to breaking laws, so more monitoring points can be set. Pre-breaks could be found through the appearance of inflection point of the MMFI of monitoring point. The inflection point of the mean curve is the breakpoint.

scholarly journals Rotation of the Philippine Sea plate inferred from paleomagnetism of oriented cores taken with an ROV-based coring apparatus

2021 ◽  
Vol 73 (1) ◽  
Author(s):  
Toshitsugu Yamazaki ◽  
Shun Chiyonobu ◽  
Osamu Ishizuka ◽  
Fumisato Tajima ◽  
Naoki Uto ◽  
...  
Keyword(s):  
Plate Motion ◽  
Philippine Sea Plate ◽  
Late Oligocene ◽  
Clockwise Rotation ◽  
Polar Wander ◽  
Philippine Sea ◽  
Apparent Polar Wander Path ◽  
Paleomagnetic Study ◽  
History Of ◽  
The Mean

AbstractReconstructing the history of Philippine Sea (PHS) plate motion is important for better understanding of the tectonics of the surrounding plates. It is generally considered that the PHS plate migrated northward since Eocene, but its rotation has not been constrained well; some reconstructions incorporated a large clockwise rotation but others did not. This is mainly because the difficulty of collecting oriented rocks from the mostly submerged PHS plate hindered establishing an apparent polar wander path. In this study, we conducted a paleomagnetic study of oriented cores taken using an ROV-based coring apparatus from the Hyuga Seamount on the northern part of the Kyushu-Palau Ridge, a remnant arc in the stable interior of the PHS plate. Stepwise thermal and alternating-field demagnetizations were applied to specimens taken successively from two ~ 30 cm long limestone cores of middle to late Oligocene age, and characteristic remanent magnetization directions could be isolated. Declination and inclination of D = 51.5° and I = 39.8°, respectively, were obtained as the mean of the two cores. The easterly-deflected declination means ~ 50° clockwise rotation of the PHS plate since middle to late Oligocene. In addition, ~ 5° latitudinal change of the site is estimated from the mean inclination. The result implies that the Kyushu-Palau Ridge was located to the southwest of the present position in middle to late Oligocene, and that PHS plate rotation as well as the Shikoku and Parece Vela Basin spreading contributed to the eastward migration of the Izu-Ogasawara (Bonin) Arc to the current position.

Early Silurian paleolatitude for central Newfoundland from paleomagnetism of the Wigwam Formation

1992 ◽  
Vol 29 (8) ◽  
pp. 1652-1661 ◽  
Author(s):  
Kenneth L. Buchan ◽  
Joseph P. Hodych
Keyword(s):  
Volcanic Rocks ◽  
Opposite Polarity ◽  
Secondary Component ◽  
Lake Area ◽  
Thermal Demagnetization ◽  
Paleomagnetic Study

Redbeds and minor volcanic rocks of the Early Silurian Wigwam Formation of the Botwood Group were sampled in the Exploits Subzone of the Dunnage Zone of central Newfoundland. At 18 sedimentary and 3 volcanic sites thermal demagnetization isolated a shallow northward (or southward) magnetization (D = 356.0°, I = −16.8°; k = 12.9; α95 = 9.2°; n = 21 site means) after correction for the tilt of bedding. A positive fold test demonstrates that this remanence predates regional Siluro–Devonian folding. A primary age for the remanence is indicated by positive conglomerate tests on volcanic clasts, and reversals correlated with sedimentary stratigraphy. Antiparallel remanence directions at sites of opposite polarity indicate that the primary remanence is not partially overprinted by a secondary component. The Exploits Subzone of the Dunnage Zone is interpreted to have been at low paleolatitudes (8.5°S ± 5°) during the Early Silurian. We reached a similar conclusion for the Notre Dame Subzone of the Dunnage Zone in a previous paleomagnetic study of Early Silurian redbeds and volcanic rocks of the King George IV Lake area. The low paleolatitudes obtained for the Wigwam and King George IV Lake rocks do not differ significantly and, hence, provide no evidence for a large ocean between the two subzones in the Early Silurian. However, the azimuthal orientation of the subzones at that time is still uncertain, and an ocean with its axis oriented in a north–south direction would not be detected by the paleomagnetic method.

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