Comment On: ‘Early Silurian Palaeolatitude of the Springdale Group Redbeds of Central Newfoundland: A Palaeomagnetic Determination With A Remanence Anisotropy Test For Inclination Error’ By J. P. Hodych and K. L. Buchan

Stamatakos, John; Voo, Rob Van der; Pluijm, Ben van der; Potts, Stephen S.; Torsvik, Trond H.

doi:10.1111/j.1365-246x.1994.tb04034.x

Cited by 5 publications

(2 citation statements)

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“…Although the general equation for inclination shallowing correction of red beds is different from the magnetite equation (Tan 2001; Tan & Kodama 2002a), for an infinite ‘ a ’ factor for magnetite and haematite particles, the correction equation becomes the same as . Stamatakos et al (1994) have criticized Hodych & Buchan's approach because the magnetic field used did not saturate the magnetization of the sample so that not all the magnetic grains (including the characteristic remanent magnetization, ChRM‐carrying particles) had been magnetically activated. The single‐component IRM technique does not allow the anisotropy tensor to be determined.…”

Section: Introductionmentioning

confidence: 99%

“…(2). Stamatakos et al (1994) have criticized Hodych & Buchan's approach because the magnetic field used did not saturate the magnetization of the sample so that not all the magnetic grains (including the characteristic remanent magnetization, ChRM-carrying particles) had been magnetically activated. The single-component IRM technique does not allow the anisotropy tensor to be determined.…”

Section: Introductionmentioning

confidence: 99%

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Laboratory depositional and compaction-caused inclination errors carried by haematite and their implications in identifying inclination error of natural remanence in red beds

Tan

Kodama

Fang

2002

Geophysical Journal International

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Summary Undetected depositional and/or compaction‐caused inclination errors may result in an overestimation of tectonically caused latitudinal offset. Hodych & Buchan used a single‐component isothermal remanent magnetization (IRM) acquired in a DC field at a 45° angle to the bedding to test for inclination errors in Silurian red beds. This approach was criticized by Stamatakos et al. We produced synthetic depositional and compaction‐caused inclination errors to test Hodych and Buchan's approach. Red bed samples collected from the Eocene Suweiyi Formation, Tarim Basin (northwest China) were disaggregated using an ultrasonic cleaner and the sediments were mixed with distilled water to make a sediment slurry. The sediment slurry spontaneously separated into silt‐dominated and clay‐sized parts, so deposition and compaction experiments were conducted with three categories of slurries: coarse grained, the fine grained and a 1:1 volume ratio mixture of the coarse‐ and fine‐grained slurries. During compaction clay‐sized sediments experienced 17°–19° inclination shallowing at 58° magnetic field inclination, while coarser sediments showed little laboratory compaction‐caused inclination error. Acquisition of IRM, coercivity spectra and unblocking temperature spectra reveal that the magnetic carrier for the fine‐grained sample is dominated by pigmentary haematite. A deposition experiment was also conducted with the coarse‐grained sediments, which showed a range of depositional inclination error, ∼0°–30°, carried by larger high unblocking temperature/coercivity particles. The intermediate unblocking temperature (or coercivity) component carried presumably by pigmentary haematite is an accurate record of the ambient magnetic field direction. Our data indicate that the single‐component IRM method of Hodych & Buchan can be used to identify and correct for the compaction‐caused inclination error of the fine‐grained samples, while it failed to detect any depositional inclination error in the coarse‐grained samples. Therefore, to better quantify the inclination error in red beds, it is suggested that multiple IRMs be measured in various directions.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Laboratory depositional and compaction-caused inclination errors carried by haematite and their implications in identifying inclination error of natural remanence in red beds

Tan

Kodama

Fang

2002

Geophysical Journal International

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2012

Paleomagnetism of Sedimentary Rocks

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Paleomagnetism and magnetic fabrics from the Springdale and Wigwam Redbeds of Newfoundland and their implications for the Silurian paleolatitude controversy

Stamatakos¹,

Lessard²,

Pluijm³

et al. 1995

Earth and Planetary Science Letters

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In many mobile belts, paleomagnetic directions from elastic sedimentary rocks are typically shallower than directions from associated igneous rocks. This discordance raises questions about the reliability of sedimentary rocks and can lead to controversial paleogeographic reconstructions. In Newfoundland, the controversy over Silurian paleogeography arises from a difference between results from elastic redbeds (with anomalously shallow directions that place Newfoundland at the paleoequator in the Silurian) and coeval epicontinental volcanics (with steeper directions that place Newfoundland at a more southerly paleolatitude). This study tests the possibility that the anomalously shallow redbed directions are the result of internal strain or inclination error related to deposition. We specifically compare coarse-and fine-grained lithologies under the assumption that such remanence-altering effects will be different in rocks with differing mechanical competence.We show that inclinations correlate with lithologic variations, but in a manner opposite to that predicted for the accumulation of internal strain. Based upon a strict set of demagnetization criteria, clearly defined single-component characteristic directions are only observed in the finer grained sandstones. These well-determined directions yield a pre-folding and pre-rotational dual polarity magnetization that places Newfoundland at a paleolatitude of 23"(S) f 9" in the Silurian. This revised paleolatitude is consistent with the volcanic results and with the paleolatitude predicted for Newfoundland from the North American reference path. In contrast, coarse-grained sandstones yield shallower directions that appear to be composites of opposite polarity magnetizations or weakly defined directions with strongly contaminating overprints. Because the shallow magnetizations in the coarser grained samples may have originated as a depositional remanence, we also suspect inclination error related to deposition. The degree of inclination error is consistent with values predicted for redbeds from previously published experimental results. These observations suggest that grain-size considerations are important in assessing the reliability of redbed magnetizations. Recognition of the relationship between grain size and remanence acquisition allows us to resolve the Silurian paieolatitude controversy for Newfoundland.

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Comment On: ‘Early Silurian Palaeolatitude of the Springdale Group Redbeds of Central Newfoundland: A Palaeomagnetic Determination With A Remanence Anisotropy Test For Inclination Error’ By J. P. Hodych and K. L. Buchan

Cited by 5 publications

References 24 publications

Laboratory depositional and compaction-caused inclination errors carried by haematite and their implications in identifying inclination error of natural remanence in red beds

Laboratory depositional and compaction-caused inclination errors carried by haematite and their implications in identifying inclination error of natural remanence in red beds

References

Paleomagnetism and magnetic fabrics from the Springdale and Wigwam Redbeds of Newfoundland and their implications for the Silurian paleolatitude controversy

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