A paleomagnetic and rock magnetic study of Tertiary volcanics from the Vogelsberg (Germany)

Sherwood, Graham J.

doi:10.1016/0031-9201(90)90190-9

Cited by 8 publications

(11 citation statements)

References 12 publications

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“…This type of behaviour had been reported in a sample of Miocene basalt from Germany rich in primary ilmenite by Sherwood (1990). (Radhakrishnamurty et al 1977).…”

Section: Magnetic Susceptibility At Low Temperaturesmentioning

confidence: 82%

“…In addition to these groups, we found during this study another distinctive type of curve in several samples, which is a combination of groups 1 and 2 (Sherwood 1990;Shaw et al 1991), and these we named group 4, where the samples show an initial decrease in susceptibility, followed by a later increase with increasing temperature.…”

Section: Magnetic Susceptibility At Low Temperaturesmentioning

confidence: 93%

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Palaeosecular variation in Central Mexico over the last 30 000 years: the record from lavas

González

Sherwood

Böhnel

et al. 1997

Geophysical Journal International

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S U M M A R Y 13 lava flows of known age (ages from I4C dating), which have been erupted in the last 30000 years, have been studied to determine the palaeosecular variation of the geomagnetic field in Central Mexico. Samples were taken from two different monogenetic volcanic fields: the Michoacan-Guanajuato volcanic field (six sites) and the Chichinautzin Formation (seven sites), both part of the Transmexican Volcanic Belt. The lavas were studied in detail using rock magnetic methods (magnetic susceptibility at room temperature, low-temperature susceptibility behaviour, hysteresis loops, Curie temperatures), combined with reflected light microscopy, in order to deduce their magnetic mineralogy and the domain states of the magnetic minerals. The magnetic carriers are titanomagnetites, which show differing degrees of high-temperature deuteric oxidation, and seem to be predominantly pseudo-single domain (PSD), though in many cases are probably a mixture of domain states. Mean palaeomagnetic directions and palaeointensity values using Shaw and Thellier techniques were obtained using several specimens from each flow. Our data seem to indicate a sharp easterly swing in declination about 5000 years ago, which is also observed in lake sediments from Central Mexico. The calculated values of the virtual dipole moment (VDM) range from 3.1 to 14.9 x A m2. Our data indicate that the virtual dipole moment seems to have increased gradually in magnitude over the last 30 kyr, with a peak at about 9000 years BP. These are features that have been observed in other parts of the globe and are probably caused by variations in the dipole part of the geomagnetic field.

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“…This type of behaviour had been reported in a sample of Miocene basalt from Germany rich in primary ilmenite by Sherwood (1990). (Radhakrishnamurty et al 1977).…”

Section: Magnetic Susceptibility At Low Temperaturesmentioning

confidence: 82%

Section: Magnetic Susceptibility At Low Temperaturesmentioning

confidence: 93%

Palaeosecular variation in Central Mexico over the last 30 000 years: the record from lavas

González

Sherwood

Böhnel

et al. 1997

Geophysical Journal International

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“…Other reference poles give similar results. For instance, the Vogelsberg volcanics of Germany have radiometric ages of 15.5–18 Ma (Sherwood 1990), which make them almost exactly coeval with the Lesbos volcanics. A slight recalculation (to combine duplicate directions and eliminate sites with poor precision) yields a palaeomagnetic pole for the Vogelsberg volcanics at 85.9°N, 258.6°E, with N = 30 and A 95 = 7.1°.…”

Section: The Reference Polementioning

confidence: 99%

“…Using this pole yields a flattening of 7.1° ± 6.8°. Results of seven studies from volcanic rocks (13–20 Ma) from central Europe summarized by Sherwood (1990) give a mean pole at 80.0°N, 137.1°E, A 95 = 5.2°. Referred to this pole, the inclination of the Lesbos volcanics is shallow by 5.6° ± 5.7°.…”

Section: The Reference Polementioning

confidence: 99%

The palaeomagnetism of Lesbos, NE Aegean, and the eastern Mediterranean inclination anomaly

Beck

Burmester

Kondopoulou

et al. 2001

Geophysical Journal International

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SUMMAR YPalaeomagnetic results for 44 sites in 16-22 Ma volcanic rocks from Lesbos, NE Aegean, yield a mean pole at 81.8uN, 178.1uE, K=9.0, A 95 =7.6u. The mean direction for these sites (D=4.3u, I=48.5u, k=10.8, a 95 =6.9u) is 5.9ut6.1u shallower than the reference direction for Miocene Lesbos calculated from Besse & Courtillot (1991). Combining these new data with previous work yields a mean inclination that is 5.6ut4.7u too shallow. Experimental problems, magnetic anisotropy, the magnetic terrain effect, geomagnetic anomalies, and problems with the reference path all seem unable to account for this observation. Shallow inclinations are a common feature of the Aegean region: 17 of 18 palaeomagnetic studies on Cenozoic igneous rocks have returned an inclination that is shallower than expected. Northward motion of the Aegean block by y500 km with respect to northern Europe would account for this observation.

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“…With collections of younger rocks, the majority of samples have shown group one low temperature behaviour, indicating the presence of Ti-rich titanomagnetite or SD magnetite (e.g. SHERWOOD, 1988SHERWOOD, , 1990. However, the degree of deuteric oxidation can affect the lowtemperature susceptibility behaviour.…”

Section: ) Diskomentioning

confidence: 99%

The Strength of the Geomagnetic Field at the Cretaceous-Tertiary Boundary: Palaeointensity Results from the Deccan Traps(India)and the Disko Lavas(Greenland).

Shaw¹,

Sherwood²,

Mussett³

et al. 1991

J. geomagn. geoelec

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A paleomagnetic and rock magnetic study of Tertiary volcanics from the Vogelsberg (Germany)

Cited by 8 publications

References 12 publications

Palaeosecular variation in Central Mexico over the last 30 000 years: the record from lavas

Palaeosecular variation in Central Mexico over the last 30 000 years: the record from lavas

The palaeomagnetism of Lesbos, NE Aegean, and the eastern Mediterranean inclination anomaly

The Strength of the Geomagnetic Field at the Cretaceous-Tertiary Boundary: Palaeointensity Results from the Deccan Traps(India)and the Disko Lavas(Greenland).

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