The use of the ‘Kono perpendicular applied field method’ in microwave palaeointensity experiments

Hill, Mimi J.; Shaw, John

doi:10.1186/bf03352734

Cited by 16 publications

(16 citation statements)

References 28 publications

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“…Other methods based upon Thellier double heating principles are classed as 'Other double heating' , e.g., the method of Walton (1977). We accommodate Microwave variants of the (Thellier and Thellier (1959) and Coe (1967b) protocols (e.g., Hill and Shaw 1999;Shaw et al 1996, which we call 'Microwave double heating') and the microwave variant of the perpendicular method (Kono and Ueno 1977;Thellier 1941), called 'Microwave single heating' (see Hill and Shaw (2007)). Suttie et al (2010) provides a discussion on the physical basis of microwave demagnetization.…”

Section: Paleointensity Metadatamentioning

confidence: 99%

GEOMAGIA50.v3: 1. general structure and modifications to the archeological and volcanic database

et al. 2015

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Background: GEOMAGIA50.v3 is a comprehensive online database providing access to published paleomagnetic, rock magnetic, and chronological data from a variety of materials that record Earth's magnetic field over the past 50 ka.Findings: Since its original release in 2006, the structure and function of the database have been updated and a significant number of data have been added. Notable modifications are the following: (1) the inclusion of additional intensity, directional and metadata from archeological and volcanic materials and an improved documentation of radiocarbon dates; (2) a new data model to accommodate paleomagnetic, rock magnetic, and chronological data from lake and marine sediments; (3) a refinement of the geographic constraints in the archeomagnetic/volcanic query allowing selection of particular locations; (4) more flexible methodological and statistical constraints in the archeomagnetic/volcanic query; (5) the calculation of predictions of the Holocene geomagnetic field from a series of time varying global field models; (6) searchable reference lists; and (7) an updated web interface. This paper describes general modifications to the database and specific aspects of the archeomagnetic and volcanic database. The reader is referred to a companion publication for a description of the sediment database. Conclusions:The archeomagnetic and volcanic part of GEOMAGIA50.v3 currently contains 14,645 data (declination, inclination, and paleointensity) from 461 studies published between 1959 and 2014. We review the paleomagnetic methods used to obtain these data and discuss applications of the data within the database. The database continues to expand as legacy data are added and new studies published. The web-based interface can be found at http:// geomagia.gfz-potsdam.de.

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Section: Paleointensity Metadatamentioning

confidence: 99%

GEOMAGIA50.v3: 1. general structure and modifications to the archeological and volcanic database

et al. 2015

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“…Microwave PI experiments were carried out using the perpendicular field method (Kono & Ueno 1977; Hill & Shaw 2007). Microwave demagnetization was initially applied in a zero‐field using stepwise increasing power levels until reaching a stable remanence direction, generally reducing the NRM by 10–20 per cent.…”

Section: Methods and Instrumentsmentioning

confidence: 99%

“…Details of the experimental procedure can be found elsewhere (e.g. Böhnel et al 2003; Hill et al 2002a, 2007; Gratton 2004).…”

Section: Methods and Instrumentsmentioning

confidence: 99%

“…Microwave PI experiments were carried out using the perpendicular field method (Kono & Ueno 1977;Hill & Shaw 2007). Microwave demagnetization was initially applied in a zero-field ,4.…”

Section: E T H O D S a N D I N S T Ru M E N T Smentioning

confidence: 99%

“…Details of the experimental procedure can be found elsewhere (e.g. Böhnel et al 2003;Hill et al 2002aHill et al , 2007Gratton 2004). Although temperatures could not be measured directly, it is reasonable that bulk sample heating remained <200 • C based on earlier experiments (Gratton 2004).…”

Section: Figurementioning

confidence: 99%

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Comparison between the microwave and multispecimen parallel difference pTRM paleointensity methods

Böhnel¹,

Dekkers²,

Delgado-Argote³

et al. 2009

Geophysical Journal International

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SUMMARY The San Quintín volcanic field (SQVF) in Baja California (Mexico) consists of at least 13 volcanic complexes with about 30 lava flows. 40Ar/39Ar step‐heating and 3He surface exposure dating experiments suggest eruption ages between 22 and 165 ka. Paleodirections of 14 flows reported here are consistent with normal secular variation. Because of low Curie temperatures and thermal alteration starting at ∼350 °C, classical Thellier–Thellier paleointensity (PI) experiments were deemed unsuccessful. Microwave PI experiments were carried out on 139 samples with 97 being interpreted to be successful, yielding values smaller than 20 μT for all sites and averaging 16.5 μT. Another sample set was studied with the multispecimen parallel differential pTRM method; temperatures for acquisition of pTRM were chosen between 200—and 225 °C. In two cases of higher unblocking temperatures, it was set at 480 °C. The experiments were successful for 104 out of 120 specimens with PI values ranging between 14 and 21 μT and clustering around 18 μT. Three noticeably higher values between 28 and 35.7 μT were obtained. Both methods yield in general well comparable PI data with the microwave PI showing a tendency to be slightly smaller than those from the multispecimen PI. The reason for it is presently not known with certainty. Possible causes include 1) incipient thermal alteration, anticipated to be slightly more prominent in the multispecimen method. 2) Cooling time effects: the microwave method involves heating during only 10–30 s compared to 2400 or more seconds in the multispecimen method. This may account for a relative underestimate of the field intensity by about 4 per cent. 3) A general PI underestimate (by ∼4 per cent) inherent to the microwave perpendicular field method applied to multidomain particles in comparison to parallel field methods. 4) A PI overestimate for small multidomain particles in the multispecimen method. However, both PI methods produced very similar results even for difficult materials as the SQVF lavas giving credit to the veracity of the obtained PI values. The multispecimen parallel differential pTRM paleointensity method thus presents a valuable alternative for traditional thermal PI determinations, as it can be applied using standard laboratory equipment. The microwave paleointensity method may yield better results but requires specialized equipment not yet available commercially.

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Unbiased analysis of geomagnetic data sets and comparison of historical data with paleomagnetic and archeomagnetic records

Arneitz

Egli

Leonhardt

2017

Reviews of Geophysics

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Reconstructions of the past geomagnetic field provide fundamental constraints for understanding the dynamics of the Earth's interior, as well as serving as basis for magnetostratigraphic and archeomagnetic dating tools. Such reconstructions, when extending over epochs that precede the advent of instrumental measurements, rely exclusively on magnetic records from archeological artifacts, and, further in the past, from rocks and sediments. The most critical component of such indirect records is field intensity because of possible biases introduced by material properties and by laboratory protocols, which do not reproduce exactly the original field recording conditions. Large biases are usually avoided by the use of appropriate checking procedures; however, smaller ones can remain undetected in individual studies and might significantly affect field reconstructions. We introduce a new general approach for analyzing geomagnetic databases in order to investigate the reliability of indirect records. This approach is based on the comparison of historical records with archeomagnetic and volcanic data, considering temporal and spatial mismatches with adequate weighting functions and error estimation. A good overall agreement is found between indirect records and historical measurements, while for several subsets systematic bias is detected (e.g., inclination shallowing of lava records). We also demonstrate that simple approaches to analyzing highly inhomogeneous and internally correlated paleomagnetic data sets can lead to incorrect conclusions about the efficiency of quality checks and corrections. Consistent criteria for selecting and weighting data are presented in this review and can be used to improve current geomagnetic field modeling techniques.

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The use of the ‘Kono perpendicular applied field method’ in microwave palaeointensity experiments

Cited by 16 publications

References 28 publications

GEOMAGIA50.v3: 1. general structure and modifications to the archeological and volcanic database

GEOMAGIA50.v3: 1. general structure and modifications to the archeological and volcanic database

Comparison between the microwave and multispecimen parallel difference pTRM paleointensity methods

Unbiased analysis of geomagnetic data sets and comparison of historical data with paleomagnetic and archeomagnetic records

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