Instantaneous record of the geomagnetic field direction of various facies from pyroclastic flow deposits: Tests for consistency in paleomagnetic directions

Uno, Koji; Furukawa, Kuniyuki; Ando, Hayato; Shinmura, Taro; Miyoshi, Masaya

doi:10.1016/j.pepi.2014.08.001

Cited by 4 publications

(3 citation statements)

References 41 publications

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“…The aerial volcanic breccia cools down faster than lava flows and might begin to acquire the TRM before the deposition of the unit ceases (Porreca et al 2006). Our interpretation for F1 unit differs from the aerial deposits, since aerial welded tuff deposits provide clustered paleomagnetic data (Uno et al 2014). It is difficult to detect any possible tilting with F1 unit, but it is considered unlikely since F2 and F3…”

Section: Paleomagnetic Data Are "Untilted"mentioning

confidence: 71%

“…Therefore, paleomagnetic data are used to calculate temperatures of emplacement (Porreca et al 2006). Recently, it has been suggested that densely welded pyroclastic deposits record accurately the ambient geomagnetic field direction at the time of emplacement; on the contrary, non-welded pyroclastic deposits show large confidence limits or deviations from their expected directions due to modification of remanence direction introduced from random rotations of remanence-carrying material during syn-or postdepositional stages (Uno et al 2014).…”

Section: And References Therein) As An Example Inmentioning

confidence: 99%

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Paleomagnetism from Deception Island (South Shetlands archipelago, Antarctica), new insights into the interpretation of the volcanic evolution using a geomagnetic model

Oliva‐Urcia

Gil-Peña

Maestro

et al. 2015

Int J Earth Sci (Geol Rundsch)

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Deception Island shows the most recent exposed active volcanism in the northern boundary of the Bransfield Trough. The succession of the volcanic sequence in the island is broadly divided into pre-and post-caldera collapse units although a well-constrained chronological identification of the well-defined successive volcanic episodes is still needed. A new paleomagnetic investigation was carried out on 157 samples grouped in 20 sites from the volcanic deposits of Deception Island (South Shetlands archipelago, Antarctic Peninsula region) distributed in: (1) volcanic breccia (3 sites) and lavas (2 sites) prior to the caldera collapse; (2) lavas emplaced after the caldera collapse (10 sites); and (3) dikes cutting pre-and the lowermost post-caldera collapse units (5 sites). The information revealed by paleomagnetism provides new data about the evolution of the multi-episodic volcanic edifice of this Quaternary volcano, suggesting that the present-day position of the volcanic materials is close to their original emplacement position. The new data have been combined with previous paleomagnetic results in order to tentatively propose an age when comparing the paleomagnetic data with a global geomagnetic model. Despite the uncertainties in the use of averaged paleomagnetic data per volcanic units, the new data in combination with tephra occurrences noted elsewhere in the region suggest that the pre-caldera units (F1 and F2) erupted before 12,000 year BC, the caldera collapse took place at about 8300 year BC, and postcaldera units S1 and S2 are younger than 2000 year BC.

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Section: Paleomagnetic Data Are "Untilted"mentioning

confidence: 71%

Section: And References Therein) As An Example Inmentioning

confidence: 99%

Paleomagnetism from Deception Island (South Shetlands archipelago, Antarctica), new insights into the interpretation of the volcanic evolution using a geomagnetic model

Oliva‐Urcia

Gil-Peña

Maestro

et al. 2015

Int J Earth Sci (Geol Rundsch)

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“…In general, glassy lithologies such as vitrophyre tend often to have a shallower direction than the lithoidal zone ( Figure 2). Mechanisms proposed to account for discrepant paleomagnetic directions in ignimbrites elsewhere have included sub-blocking-temperature grain rotation [Geissman, 1980;Rosenbaum, 1986;Uno et al, 2014], chemical remagnetization during devitrification [Reynolds, 1977], secular variation during Journal of Geophysical Research: Solid Earth 10.1002/2014JB011868 prolonged cooling [Wells and Hillhouse, 1989], and large magnetic anisotropy [Gattacceca and Rochette, 2002]. Most of these ignimbrites are significantly less-intensely welded than Snake River (SR)-type ignimbrites.…”

Section: Introductionmentioning

confidence: 99%

Magnetic anisotropy in rhyolitic ignimbrite, Snake River Plain: Implications for using remanent magnetism of volcanic rocks for correlation, paleomagnetic studies, and geological reconstructions

et al. 2015

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Individual ignimbrite cooling units in southern Idaho display significant variation of magnetic remanence directions and other magnetic properties. This complicates paleomagnetic correlation. The ignimbrites are intensely welded and exhibit mylonite-like flow banding produced by rheomorphic ductile shear during emplacement, prior to cooling below magnetic blocking temperatures. Glassy vitrophyric lithologies commonly have discrepantly shallow remanence directions rotated closer to the orientation of the subhorizontal shear fabric when compared to the microcrystalline center of the same cooling unit. To investigate this problem, we conducted a detailed paleomagnetic and rock magnetic study of a vertical profile through a single ignimbrite cooling unit and its underlying baked soil. The results demonstrate that large anisotropy of thermal remanent magnetization correlates with large (up to 38°) deflections of the stable remanence direction. Anisotropy of magnetic susceptibility revealed no strong anisotropy. A strong lineation and deflection of the remanence declination suggest that rheomorphic shear above magnetic blocking temperatures is the dominant mechanism controlling the formation of the magnetic fabric, with compaction contributing to a lesser extent. Nucleation and growth of anisotropic fine-grained magnetite in volcanic glass at high temperatures after, and perhaps also during, emplacement is indicated by systematic variation of magnetic properties from the quickly chilled ignimbrite base to the interior. These properties include remanence directions, anisotropy, coercivity, susceptibility, strength of natural remanent magnetization, and dominant unblocking temperature. The microcrystalline ignimbrite center has a magnetic direction that is the same as the underlying baked soil and, therefore, is a more reliable recorder of the paleofield direction than the glassy margins of highly welded ignimbrites.

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Timing of the martian dynamo: New constraints for a core field 4.5 and 3.7 Ga ago

et al. 2020

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The absence of crustal magnetic fields above the martian basins Hellas, Argyre, and Isidis is often interpreted as proof of an early, before 4.1 billion years (Ga) ago, or late, after 3.9 Ga ago, dynamo. We revisit these interpretations using new MAVEN magnetic field data. Weak fields are present over the 4.5-Ga old Borealis basin, with the transition to strong fields correlated with the basin edge. Magnetic fields, confined to a near-surface layer, are also detected above the 3.7-Ga old Lucus Planum. We conclude that a dynamo was present both before and after the formation of the basins Hellas, Utopia, Argyre, and Isidis. A long-lived, Earth-like dynamo is consistent with the absence of magnetization within large basins if the impacts excavated large portions of strongly magnetic crust and exposed deeper material with lower concentrations of magnetic minerals.

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Instantaneous record of the geomagnetic field direction of various facies from pyroclastic flow deposits: Tests for consistency in paleomagnetic directions

Cited by 4 publications

References 41 publications

Paleomagnetism from Deception Island (South Shetlands archipelago, Antarctica), new insights into the interpretation of the volcanic evolution using a geomagnetic model

Paleomagnetism from Deception Island (South Shetlands archipelago, Antarctica), new insights into the interpretation of the volcanic evolution using a geomagnetic model

Magnetic anisotropy in rhyolitic ignimbrite, Snake River Plain: Implications for using remanent magnetism of volcanic rocks for correlation, paleomagnetic studies, and geological reconstructions

Timing of the martian dynamo: New constraints for a core field 4.5 and 3.7 Ga ago

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