Analysis of palaeomagnetic inclination data

McFadden, P. L.; Reid, Alan

doi:10.1111/j.1365-246x.1982.tb04950.x

Cited by 332 publications

(226 citation statements)

References 6 publications

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“…Special statistics must be used to calculate unbiased estimates of the mean inclination. Several authors have developed methods for making such calculations (Kono, 1980;McFadden and Reid, 1982;Cox and Gordon, 1984), all of which give similar results at low latitudes. The algorithm developed by Kono (1980) was used in this study for the computation of mean inclinations, paleolatitudes, and their error limits.…”

Section: Paleolatitudesmentioning

confidence: 99%

Paleomagnetism of Ocean Drilling Program Leg 101 Sediments: Magnetostratigraphy, Magnetic Diagenesis, and Paleolatitudes

Sager¹

1988

Proceedings of the Ocean Drilling Program

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Paleomagnetic measurements were made on 913 samples from 11 holes (626B, 626C, 627B, 628A, 630A, 631A, 632A, 632B, 633A, 634A, and 635B) drilled in and around the Bahamas carbonate bank during Ocean Drilling Program Leg 101. These samples displayed a wide range of magnetic intensities (from about 1.0 A/m to 1.6 x I0-6 A/m) and magnetic behavior. Most samples were weakly magnetized and had low mean destructive fields; however, sediments from sections of several holes were strongly magnetic with stable magnetizations. Magnetic-polarity interpretations were made on a Campanian unit from Hole 627B, a mid-Oligocene unit from Hole 628A, and a Plio-Pleistocene section from Hole 633A. Sediments in the upper parts of Holes 627B, 632A, and 633A have high magnetic intensities that decay 2 to 3 orders of magnitude over depths of 5 to 18 mbsf. The pattern of decline of the magnetism and the change in mean destructive fields and geochemical conditions in these holes are consistent with diagenetic dissolution of the magnetic minerals in a suboxic or anoxic-sulfidic environment. Paleolatitudes were calculated from samples from 16 time units in 7 holes and compared to the apparent polar wander path of the North American plate. INTRODUCTIONThe scientific objectives of Ocean Drilling Program (ODP) Leg 101 were to investigate the evolution of the modern Bahamian carbonate platform and the depositional history of its sediments. Nineteen holes were drilled at 11 sites (Sites 626-636) in 4 regions of the northern Bahamas (Fig. 1) Although it was expected that the carbonate sediments of the Bahamas might be only weakly magnetic and thus difficult to Paleomagnetically measure and analyze, the promise of exceptional biostratigraphic and stable isotope age constraints on these sediments provided further impetus for this study. Moreover, much of the coring was done using the advanced hydraulic piston corer (APC); numerous recent paleomagnetic studies have shown that sediments recovered with a similar system (HPC) used during DSDP drilling yielded excellent paleomagnetic results (e.g., Spariosu, 1982a, 1982b;Tauxe et al., 1984;Chave, 1984;Weinreich and Theyer, 1985). The objectives of this study were twofold. One goal was to determine the magnetic stratigraphy of several holes in order to provide age constraints for sedimentary studies as well as new information about correlation of biostratigraphic, stable isotope, and magnetic polarity time scales. Important magnetostratigraphic studies have been done on sediments of Cretaceous age from nearby DSDP Site 534 on the Blake Plateau (Ogg, 1985;Ogg and Lowrie, 1986). The other objective was to calculate paleolatitudes of various ages to be used for studies of tectonics and the longterm behavior of the geomagnetic field.Nine hundred thirteen samples were obtained for paleomagnetic study from Leg 101 cores. Holes 627B, 628A, 631 A, 632A, Austin, J. A., Schlager, W., et al., 1988. Proc. ODP, Sci. Results, 101: College Station, TX (Ocean Drilling Program).2 Departments of Oceanography and G...

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Section: Paleolatitudesmentioning

confidence: 99%

Paleomagnetism of Ocean Drilling Program Leg 101 Sediments: Magnetostratigraphy, Magnetic Diagenesis, and Paleolatitudes

Sager¹

1988

Proceedings of the Ocean Drilling Program

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“…Although the stable remanent inclinations from Site 920 are broadly similar to the expected GAD inclination for the MARK area, the mean inclination (34°, n = 200, α = 1°; calculated using the method of McFadden and Reid, 1982) is statistically distinct from either the dipole (41°) or the present IGRF inclination (-42°). Acquisition of a thermoremanent magnetization may be deflected in rocks having a significant magnetic anisotropy (-5% magnetic anisotropy or Pj = 1.09 may lead to 3° remanence deflection; Stacey and Banerjee [1974]).…”

Section: Results Of Magnetic Measurementsmentioning

confidence: 91%

“…Although the origin of magnetic anisotropy in serpentinized peridotites may be complex (e.g., MacDonald andEllwood, 1988), documentation of the relationship between the magnetic and mesoscopic fabrics may ultimately allow the use of AMS data to characterize more subtle variations in the three-dimensional fabric than would be possible from petrographic studies alone. Furthermore, the consistency of the stable remanent inclinations (34°, α = 1°; where α is the half-angle of the asymmetric 95% confidence interval; McFadden and Reid, 1982) in samples from Site 920 and the overall similarity of this inclination to that expected from a geocentric axial dipole (GAD = 41°) suggest 'Karson, J.A., Cannat, M., Miller, D.J., and Elthon, D. (Eds.…”

Section: Introductionmentioning

confidence: 99%

Magnetic anisotropy in serpentinized peridotites from Site 920: its origin and relationship to deformation fabrics

Lawrence¹,

Gee²,

Hurst³

1997

Proceedings of the Ocean Drilling Program

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Anisotropy of magnetic susceptibility (AMS) measurements on serpentinized peridotites from Ocean Drilling Program Site 920 reveal a strong magnetic "fabric," typically characterized by an oblate susceptibility ellipsoid. Curie temperatures and maximum unblocking temperatures near 580°C, as well as petrographic observations, suggest that magnetite is the sole magnetic carrier in the serpentinites. Because the magnetic mineralogy is dominated by coarse-grained magnetite, the susceptibility ellipsoid should provide a three-dimensional image of the average elongation of magnetite grains or grain clusters. Petrographic studies of three orthogonal thin sections from a limited number of samples indicate that the preferred shape orientation of magnetite grain clusters correlates well with the apparent susceptibility maxima and minima in these planes. The magnetite longaxis preferred orientation is typically within -20° of the maximum principal axis of the susceptibility ellipsoid. The close correspondence between the magnetic foliation and the orientation of magnetite-bearing serpentine veins, together with the petrographic evidence for the distribution of magnetite, suggests that the magnetic "fabric" is primarily a reflection of the orientation of these veins. Hence, the AMS ellipsoid may be a more accurate descriptor of the integrated three-dimensional vein orientations than visual orientation measurements made on the split cores.

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“…3). Accounting for biases in inclination averages using the method of McFadden and Reid (1982), the mean of the normal polarity data (/" = -29.9°…”

Section: Paleolatitude Datamentioning

confidence: 99%

Early Cretaceous Magnetostratigraphy and Paleolatitudes from the Mid-Pacific Mountains: Preliminary Results Bearing on Guyot Formation and Pacific Plate Translation

Tarduno¹,

Sager²,

Nogi³

1995

Proceedings of the Ocean Drilling Program, 143 Scientific Results

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Detailed thermal demagnetization experiments applied to some weakly magnetized shallow-water carbonates recovered at Site 866 (991-1622 mbsf) yield a characteristic remanent magnetization having maximum unblocking temperatures of 500° to 580°C, after the removal of one or more overprints. Alternating field (AF) demagnetization yields a similar characteristic component. This magnetization shows both polarities, which form 10 polarity zones that we correlate to the upper Mesozoic "M-sequence" of the marine magnetic anomaly record. Using tie points derived from paleontologic and isotopic studies, we tentatively assign the polarity zones to CM1 through CM7. Such an assignment requires that basement at Site 866 be of M7 age (or older), broadly consistent with radiometric age data that suggest an age of 128 Ma. Using this interpretation, at least one major hiatus and several substantial changes in sedimentation rate are required in the carbonate sequence.Paleolatitude data from the Site 866 carbonates (14.6°S) are within error of an early Aptian data set from nearby Site 463 (13°S), suggesting little (or no) latitudinal transport during the later part of the Early Cretaceous. Comparisons with younger data sets also suggest that total latitudinal translation from the time of edifice formation to the mid-Cretaceous was minor (±5°). These data do not support drift toward extreme southerly latitudes as a cause of platform drowning. This near-stationary behavior of the Pacific Plate over an area of vigorous mantle convection may account for some patterns of subsidence that are implied by the magnetostratigraphic data.

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Analysis of palaeomagnetic inclination data

Cited by 332 publications

References 6 publications

Paleomagnetism of Ocean Drilling Program Leg 101 Sediments: Magnetostratigraphy, Magnetic Diagenesis, and Paleolatitudes

Paleomagnetism of Ocean Drilling Program Leg 101 Sediments: Magnetostratigraphy, Magnetic Diagenesis, and Paleolatitudes

Magnetic anisotropy in serpentinized peridotites from Site 920: its origin and relationship to deformation fabrics

Early Cretaceous Magnetostratigraphy and Paleolatitudes from the Mid-Pacific Mountains: Preliminary Results Bearing on Guyot Formation and Pacific Plate Translation

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