A new fold test for palaeomagnetic studies

McFadden, P. L.

doi:10.1111/j.1365-246x.1990.tb01761.x

Cited by 577 publications

(478 citation statements)

References 21 publications

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“…In such cases (localities 10 and 13, see Table 2) the mean paleomagnetic directions for a given locality were determined in three different ways. One was based on linear segments, the second was calculated from the last meaningful demagnetization steps, and the third was based on the combination of stable vectors and remagnetization circles (McFadden 1990). As Table 2 documents, the three methods provided the same directions (within the error limit).…”

Section: Laboratory Measurements and Resultsmentioning

confidence: 96%

The contact zone between the ALCAPA and Tisza-Dacia mega-tectonic units of Northern Romania in the light of new paleomagnetic data

Marton¹,

Tischler

Csontos

et al. 2007

Swiss j geosci

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Paleomagnetic analyses were carried out on samples from 19 localities within two different mega-tectonic units in Northern Romania: Tisza-Dacia (11 localities) and ALCAPA (8 localities). The samples cover a range of different lithologies: (1) Late Cretaceous red-coloured marl to marly limestone, (2) EoOligocene flysch sediments, and (3) mid-Miocene (Langhian) tuffite (Dej tuff and related sediments). The Late Cretaceous and mid-Miocene specimens carry secondary paleomagnetic signals exhibiting a counter clockwise deflection of the paleo-declinations by some 30°, while the Eo-Oligocene localities indicate an overall clockwise deflected (between some 45°and >90°) paleodeclination with respect to present-day north. Clockwise rotation postdates the age of sedimentation (Lower Oligocene), as well as (at least partially) thrusting of the Pienides onto the Tisza-Dacia mega-tectonic unit, which occurred between 20.5 and 18.5 Ma. Clockwise rotation predates post-12 Ma counter clockwise rotations inferred for the mid-Miocene localities.Surprisingly, the clockwise rotations of the first rotational stage not only affected the (par-) autochthonous sedimentary cover of the Tisza-Dacia megatectonic unit, but also the allochthonous flysch nappes of the Pienides, i.e. the eastern tip of the ALCAPA mega-tectonic unit. Well-documented opposed rotation of the remainder of ALCAPA necessitates a detachment of this eastern tip of ALCAPA after 18. Die Rotation der Eo-Oligozänen Proben fand nach der Sedimentation der jüngsten Proben (unteres Oligozän), und zumindest teilweise nach dem Deckenschub der Pieniden (20.5-18.5 Ma) auf den Tisza-Dacia Block statt. Diese Rotation mit dem Uhrzeigersinn geht der durch die mittel-Miozänen Proben dokumentierten gegenläufigen Rotation (ab 12 Ma) voraus.Die Rotationen der früheren Phase wurden nicht nur in den Sedimenten aus der (par-) autochthonen Bedeckung von Tisza-Dacia, sondern auch in den überschobenen Pieniden nachgewiesen. Dieses Ergebnis ist auf den ersten Blick überraschend, da sie Teil von ALCAPA sind, der Rest von ALCAPA zu dieser Zeit aber in einem gegenläufigen Sinn, also gegen den Uhrzeigersinn, rotierte. Diese gegenläufigen Rotationen erfordern also eine tektonische Ablösung der östlichsten Spitze von ALCAPA vom Rest dieser grosstektonischen Einheit. Der wahrscheinlichste Ort für eine solche Ablösung befindet sich an den Rändern der Transkarpathischen Depression. Die zweite Rotationsphase, ca. 30°gegen den Uhrzeigersinn nach 12 Ma, ist auch aus dem OstSlovakischen Becken bekannt. Sowohl die Internen West-Karpathen westlich des Ost-Slovakischen Beckens, als auch das südliche Apuseni Gebirge, zeigen nach 12 Ma ein vom Arbeitsgebiet abweichendes Rotationsverhalten.

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Section: Laboratory Measurements and Resultsmentioning

confidence: 96%

The contact zone between the ALCAPA and Tisza-Dacia mega-tectonic units of Northern Romania in the light of new paleomagnetic data

Marton¹,

Tischler

Csontos

et al. 2007

Swiss j geosci

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“…[19] The fold test could not be effected in the LM section because the basalt flows have a monoclinal structure. However, a fold test was performed while the series at GM are combined and was positive at the 95% confidence level [McFadden, 1990], with x 2(in situ) = 27.25, x 2(tilt corrected) = 5.4, x c = 7.264 (N = 39 sites for the both sections). In the other case, reversal directions obtained from both the LM and GM sections could also be used for performing a fold test, which also passed at the 99% confidence level with x 2(in situ) = 25.27, x 2(tilt corrected) = 6.918, x c = 9.157 (N = 31 sites).…”

Section: Magnetic Results and Polarity Sequencementioning

confidence: 99%

Magnetostratigraphic constraints on two‐stage eruptions of the Emeishan continental flood basalts

Zheng

Yang

Tong³

et al. 2010

Geochem Geophys Geosyst

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[1] Temporal and spatial variations of high and low contents of Ti basalts in the Permian Emeishan large igneous province (ELIP) of southwest China and Vietnam are crucial for modeling of continental basalt formation and the nature of mantle-lithosphere interaction. A combined geochemical and magnetostratigraphic study was carried out at Yanyuan in the inner zone of the ELIP. Geochemical results indicate that the basalts are low-Ti (LT) basalts (Ti/Y ∼ 484.2-511.4) in the Luomapu section and high-Ti (HT) basalts (Ti/Y ∼ 558.2-658.9) in the Gongmushan section. Systematic paleomagnetic sampling and stepwise thermal demagnetization demonstrate that the higher temperature component shows two distinct characteristic remanent magnetizations with northeasterly upward and SWW downward directions. These results indicate a simple magnetostratigraphic normal and reversed polarity pattern from the lower and upper parts of the section, respectively. By comparing with available magnetostratigraphic and paleomagnetic data carried out in the ELIP, these results imply that the eruption of the Emeishan basalts can be divided into early (normal polarity subchron) and late (reversal subchron) stages. The early stage included LT basalts in the inner zone and most of the HT basalts in the intermediate and outer zones, and the late stage contained a part of LT and HT basalts in the upper parts of the sections in the inner zone and a few in the intermediate zone of the ELIP. Correlating with available Middle-Late Permian magnetostratigraphy and the Permian magnetic time scale, the new magnetic polarity sequence result suggests that the ELIP formed over a very short time interval (<1 Myr).

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“…Site mean directions were computed using the statistics of Fisher (1953). The statistical methods of McE1-hinny (1964) and McFadden (1990) have been used to constrain the age of magnetisation relative to the folding episodes affecting a number of drilled sequences.…”

Section: Palaeomagnetic Methodsmentioning

confidence: 99%

Evolution of the boundary between the Philippine Sea Plate and Australia: palaeomagnetic evidence from eastern Indonesia

Ali¹,

Hall

1995

Tectonophysics

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A new fold test for palaeomagnetic studies

Cited by 577 publications

References 21 publications

The contact zone between the ALCAPA and Tisza-Dacia mega-tectonic units of Northern Romania in the light of new paleomagnetic data

The contact zone between the ALCAPA and Tisza-Dacia mega-tectonic units of Northern Romania in the light of new paleomagnetic data

Magnetostratigraphic constraints on two‐stage eruptions of the Emeishan continental flood basalts

Evolution of the boundary between the Philippine Sea Plate and Australia: palaeomagnetic evidence from eastern Indonesia

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