Rock magnetism and palaeomagnetism of greigite-bearing mudstones in the Italian peninsula

Sagnotti, Leonardo; Winkler, Aldo

doi:10.1016/s0012-821x(98)00248-9

Cited by 105 publications

(99 citation statements)

References 43 publications

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“…Samples with magnetite as the main magnetic carrier always show k diff = 0 (Table 1). This provides a further experimental veri¢cation of the suitability of the k diff parameter to distinguish between greigite-bearing and magnetite-bearing sediments [19].…”

Section: Pilot Study and Rock Magnetismmentioning

confidence: 59%

“…The normalized percentage of the IRM intensity along the three axes (X%, Y% and Z%) and the maximum unblocking temperatures (T ub ) during the demagnetization treatment were used to evaluate the presence and the relative abundance of di¡erent magnetic minerals. For these samples, it was also measured the di¡er-ence in the low-¢eld magnetic susceptibility value along a given axis, induced by the application of a large (2 T) magnetic ¢eld at right angle (k diff as de¢ned by [19]). …”

Section: Sampling and Measurementsmentioning

confidence: 99%

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Paleomagnetic constraints on the Plio–Pleistocene geodynamic evolution of the external central–northern Apennines (Italy)

Sagnotti

Winkler

Alfonsi

et al. 2000

Earth and Planetary Science Letters

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We report on new paleomagnetic results obtained from 27 sites sampled in the Plio^Pleistocene sequences at the external front of the central^northern Apennines. Previous analyses of Miocene (Messinian) sediments indicated that the present shape of the northern Apenninic arc is due to the oroclinal bending of an originally straight belt oriented around N320³ and that vertical axis rotations accompanied the migration of the thrust fronts toward the Adriatic foreland [F. Speranza et al., J. Geophys. Res. 102 (1997) 3153^3166]. We tried to provide new paleomagnetic constraints for the timing and rates of the oroclinal bending process during the Pliocene and the Pleistocene. The results suggest that CCW rotations observed in the northern part of the studied area are possibly younger than 3 Ma. No regional rotation is recorded in the Pliocene and Pleistocene sediments from the southern part of the study area, analogously to the Messinian sediments of the`Acquasanta' domain of Speranza et al. [F. Speranza et al., J. Geophys. Res. 102 (1997) 3153^3166]. A local significant CCW rotation (23³ þ 10³) is identified in the Early Pleistocene sediments that crop out along the Adriatic coast between Ascoli and Pescara, indicating differential motion of the thrust sheets. This rotation must be younger than 1.43 Ma. ß

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Section: Pilot Study and Rock Magnetismmentioning

confidence: 59%

Section: Sampling and Measurementsmentioning

confidence: 99%

Paleomagnetic constraints on the Plio–Pleistocene geodynamic evolution of the external central–northern Apennines (Italy)

Sagnotti

Winkler

Alfonsi

et al. 2000

Earth and Planetary Science Letters

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“…The thermal demagnetiza tion curves of both the NRM (not shown) and the show a decrease in intensity from 200°C on, and an important unblocking at 360°C. These values are typical of greigite (Sagnotti & Winkler, 1999); the gradual decay of magnetization above 200°C is attributable to the onset of thermal decomposition of greigite. The presence of minor amounts of other ferrimagnetic Fe sulfides cannot be entirely excluded: the low and intermediate coercivity components of the composite IRM show a steplike decrease in the Michalovce sample (d) that may result from the alteration of a ferrimagnetic phase other than greigite.…”

Section: Magnetic Measurementsmentioning

confidence: 79%

“…Bulk magnetic methods are useful for identify ing ferrimagnetic Fe sulfides, particularly greigite (the most recent compilation was published by Sagnotti & Winkler, 1999); however, these studies do not provide information regarding the origin of greigite. Bulk magnetic methods can be used to detect the presence of single-domain crystals.…”

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confidence: 99%

Crystal-size distributions and possible biogenic origin of Fe sulfides

Pósfai¹,

Cziner²,

Márton³

et al. 2001

ejm

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Sedimentary greigite (Fe 3 S 4 ) can form either by "biologically controlled " or by "biologically induced min eralization " (BCM and BIM, respectively). In order to identify the origin of magnetic Fe sulfides, we studied and compared the sizes and morphologies of greigite crystals produced by a magnetotactic microorganism (previously described and referred to as the "many-celled magnetotactic prokaryote ", MMP) and Fe sulfides from two specimens of Miocene sedimentary rocks (from £±ka, in the foredeep of the Western Carpathians and from Michalovce, in the Transcarpathian Depression). Greigite grains from the MMP and the £±ka rock show nearly Gaussian crystal-siz e distributions (CSDs), whereas the CSD is lognormal for Fe sulfides from the Michalovce rock. We simulated various crystal-growth mechanisms and matched the calculated and observed CSDs; crystals from the MMP and the £±ka rock have CSDs that are consistent with random growth of crystal nuclei in an open system, whereas the CSD of the Michalovce Fe sulfides is consistent with surface-controlled growth followed by supply-controlled growth in an open system. On the basis of CSDs and characteristic contrast features in the transmission electron microscope, greigite in the £±ka rock is likely of BCM origin, whereas the Fe sulfide crystals in the other rock sample were produced by BIM processes. Our results indicate that the methods we applied in this study may contribute to the identification of the origin of magnetic Fe sulfide minerals in sedimentary rocks.

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“…on tbe u of tran mi ion lectron micro copy (TEM) and Greigite occurs in sedimentary rocks and i the primary off-axi electron holography to study the compo ition carrier of the paleomagnetic ignal in many anoxic cry tallograpby morphology and magnetic mjcro tructure environments [9]. Sedimentary greigite is either authigenic of greigite cry tal in uncultured magnetotactic bacteria or may originate from magnetotactic bacteria [10].…”

mentioning

confidence: 99%

Magnetic microstructure of iron sulfide crystals in magnetotactic bacteria from off-axis electron holography

Kasama

Pósfai

Chong

et al. 2006

Physica B: Condensed Matter

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bstractTran mi ion electron micro copy, off-axi electron holography and energy-elected imaging were u ed to tudy the crystallography, morphology, and magnetic micro tructure of nano cale greigite (Fe3S4) magnetosome in magnetotactic bacteria from a ulfidic habitat. The greigite magnetosomes were organized in chains but were less ordered than magnetite magnetosomes in other bacteria.evertheles , the magneto ome comprise a permanent magnetic dipole, sufficient for magnelotaxi .

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Rock magnetism and palaeomagnetism of greigite-bearing mudstones in the Italian peninsula

Cited by 105 publications

References 43 publications

Paleomagnetic constraints on the Plio–Pleistocene geodynamic evolution of the external central–northern Apennines (Italy)

Paleomagnetic constraints on the Plio–Pleistocene geodynamic evolution of the external central–northern Apennines (Italy)

Crystal-size distributions and possible biogenic origin of Fe sulfides

Magnetic microstructure of iron sulfide crystals in magnetotactic bacteria from off-axis electron holography

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