Mineral Magnetic Studies of Archaeological Samples: Implications for Sample Selection for Paleointensity Determinations.

Cui, Yuqing; Verosub, Kenneth L.; Roberts, Andrew; Kovacheva, Mary

doi:10.5636/jgg.49.567

Cited by 20 publications

(15 citation statements)

References 38 publications

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“…Constricted hysteresis loops (Table 2) for most of these samples also support the idea of a significant SP contribution. At this point our results contradict the conclusion of Cui et al (1997) As it was shown earlier, chemical changes in sample 2125 (Isperih) (Fig. 9a) are attributed to the growth of SP grains up to stable SD sizes, causing changes in initial magnetic capacity.…”

Section: Rock Magnetic Properties Of the Archaeological Samples And Tcontrasting

confidence: 57%

“…The same holds for pseudo-single domain (PSD) grains while the thermal demagnetization of multidomain (MD) grains exhibits "trails" , extending up to Tb of the mineral which carries the TRM (Bolshakov and Shcherbakova, 1979;Xu and Dunlop, 1994). Most of the papers dealing with this problem have considered volcanic rocks (Thomas, 1993;Haag et al, 1995) with only few studies on archaeological samples (Walton, 1984(Walton, , 1987Aitken et al, 1986Aitken et al, , 1988Cui and Verosub, 1995;Cui et al, 1997). A first attempt to examine the results of rock magnetic studies in conjunction with the success or failure of the Thellier intensity experiment was recently carried out in the laboratory of the Geophysical Institute, Sofia (Kovacheva and Toshkov, 1994).…”

Section: Introductionmentioning

confidence: 99%

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Preliminary Rock Magnetic Study of Archaeomagnetic Samples from Bulgarian Prehistoric Sites.

Jordanova

Petrovský²,

Kovacheva

1997

J. geomagn. geoelec

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Rock magnetic properties of archaeomagnetic samples taken from ovens are studied. Thermal demagnetization of saturation remanences and other studies reveal the presence of: (titano)magnetite, iron oxyhydroxides, and maghemite with Tb -650°C which is stable with respect to inversion. During thermal demagnetization the soft IRM component (0.06 T) is always the strongest one, indicating the importance of the (titano)magnetite contribution. A break-up in the values of coercivity H with respect to initial mass-specific magnetic susceptibility (X) occurs at X -1.5 x 10-6 m3/kg and separates poorer from better quality samples in the palaeointensity experiment. Separation of bad and good Thellier experiments is also observed in the relation between the coercivities and the concentration-independent parameter SIRM/X. Thus, the poor quality of the palaeointensity experiments for some samples can probably be ascribed to the presence of weathering products and MD magnetite grains while the good quality of these experiments is related to "soft" hysteresis properties and a broad unblocking temperature spectrum.

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Section: Rock Magnetic Properties Of the Archaeological Samples And Tcontrasting

confidence: 57%

Section: Introductionmentioning

confidence: 99%

Preliminary Rock Magnetic Study of Archaeomagnetic Samples from Bulgarian Prehistoric Sites.

Jordanova

Petrovský²,

Kovacheva

1997

J. geomagn. geoelec

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“…The screening would be to identify the samples with thermally stable magnetic minerals occurring in a single domain (SD) and/or pseudo single Domain (PSD) state. Application of several magnetic parameters on archaeological artifacts and their implications for sample selection in archaeointensity measurements were elaborately carried out by many authors [10][11][12][13].…”

Section: Mineral Magnetic Studiesmentioning

confidence: 99%

Mössbauer and mineral magnetic studies on archaeological potteries from Adhichanallur, Tamilnadu, India

et al. 2008

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Megalithic potteries collected from Adhichanallur, Tamilnadu, India (Lat. 8 • 44 N; Long. 77 • 42 E) have been subjected to various spectroscopic and rock magnetic studies. The type of clay, their origin, level of structural deformation due to firing, firing temperature and atmospheric condition followed during making the potteries are analyzed. The potteries were subjected to Mössbauer and X-ray diffraction studies to analyze the iron phases in them. It is found that the samples were made of local clay (red clay), fired above 600 • C under open atmospheric and/or reduced atmospheric conditions and air has been allowed during cooling. The Mössbauer spectra reveal the presence of Fe 3+ , Fe 2+ and iron oxides of hematite and magnetite. The firing temperature and firing conditions established from Mössbauer studies are similar to the observation made from FT-IR studies. The magnetic mineral types, the mass fractions and the domain states of the constituent magnetic grains were elucidated from a range of rock magnetic measurements including variation of susceptibility with low field, frequency and temperature, hysteresis parameters and isothermal remanence acquisition data. The magnetic mineralogy of most pottery samples was dominated by magnetite/(titano) magnetite, while magnetic grain size spectrum varies from very fine (super paramagnetic) to fine (stable single domain, pseudo single domain). The reversible thermo magnetic behavior reflects no mineralogical transformations during reheating and all the samples show same Curie temperature 580 • C due to magnetite. From the above information it is demonstrated that these samples are suitable for determining the reliable ancient geomagnetic field intensity values existed during that period. R. Venkatachalapathy (B) C.A.S in Marine

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“…In the literature, several pre-selection procedures before archaeointensity determinations have been proposed (e.g. Cui & Verosub 1995;Cui et al 1997;Jordanova et al 1997Jordanova et al , 2001Leonhardt et al 2004;Carvallo et al 2006). Nevertheless, some of these procedures are almost as time consuming as a Thellier experiment and a full success cannot still be guaranteed.…”

Section: Re-evaluation Of Previous Results Through Magnetic Measurementsmentioning

confidence: 99%

Investigating the archaeointensity determination success of prehistoric ceramics through a multidisciplinary approach: new and re-evaluated data from Greek collections

Kondopoulou¹,

Gómez‐Paccard

Aidona³

et al. 2017

Geophysical Journal International

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S U M M A R YThe Balkan area provides an almost continuous record of the geomagnetic field variations during the last eight millennia but important data dispersion and chronological gaps are still observed. In order to improve this pattern, we oriented our research towards the study of Greek prehistoric ceramics and pottery collections. We present here new archaeointensity and mineralogical results from pottery and ceramics collected in two Bronze Age sites in Northern Greece, corresponding to the middle third and middle second millennium BC. Thermal demagnetization experiments, thermomagnetic curves, thermal demagnetization measurements of three axes composite isothermal magnetization and first-order reversal curves (FORC) diagrams were performed in order to define the main magnetic carriers and select the most promising samples for archaeointensity determination. The results suggest that the majority of the studied materials are dominated by a mixture of superparamagnetic and stable single domain grains, with very little magnetic interactions. In almost all samples the main magnetic carrier observed is a low coercivity mineral, most probably magnetite and/or Ti-magnetite. Classical Thellier experiments, including both the thermoremanent magnetization anisotropy and cooling rate corrections were performed on the selected samples. Two new archaeointensities were obtained and compared with previous data available for Greece and neighbouring countries and with global geomagnetic field models results. In order to investigate the causes of the high rate of failure observed in our archaeointensity experiments, we re-examined the results obtained from the study of four collections already published by better characterizing the magnetic and mineralogical properties of the studied fragments. Specific hysteresis curves performed at different layers of ceramic fragments reveal an important degree of inhomogeneity. Mineralogical analysis of selected samples from the totality of six Greek prehistoric sites studied, including new X-ray powder diffraction analysis and a detailed description of the different geological contexts, is provided. The results suggest that the sherds were all fired in medium-high temperatures (mostly between 500• and 800• C). The nature of the baked clay paste in response to the local geology appears to account for a part of the variability in magnetic properties. We suggest that X-ray powder diffraction analyses and thorough examination of the geological environment in combination with a satisfactory knowledge of the corresponding excavations history might provide an additional tool to appropriately select pottery fragments before performing future archaeointensity experiments.

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Mineral Magnetic Studies of Archaeological Samples: Implications for Sample Selection for Paleointensity Determinations.

Cited by 20 publications

References 38 publications

Preliminary Rock Magnetic Study of Archaeomagnetic Samples from Bulgarian Prehistoric Sites.

Preliminary Rock Magnetic Study of Archaeomagnetic Samples from Bulgarian Prehistoric Sites.

Mössbauer and mineral magnetic studies on archaeological potteries from Adhichanallur, Tamilnadu, India

Investigating the archaeointensity determination success of prehistoric ceramics through a multidisciplinary approach: new and re-evaluated data from Greek collections

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