Directional changes of the geomagnetic field in West Africa: Insights from the metallurgical site of Korsimoro

Donadini, F.; Serneels, Vincent; Kapper, Kathrin Lisa; Kateb, Akram El

doi:10.1016/j.epsl.2015.08.030

Cited by 13 publications

(13 citation statements)

References 30 publications

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“…Some specimens from furnaces KRS04, 21, 23, 23, and 35 have two phases in their demagnetization diagrams: the first unblocking temperature is at around 200 °C and the second at 580 °C. The unblocking temperature of 200 °C resembles the HCSLT phase, observed in samples from furnace KRS04 in 3IRM measurements15 (Fig. 1f).…”

Section: Archaeointensity Resultsmentioning

confidence: 66%

“…In most of the palaeosecular variation curves we observe a small local maximum with values up to about 37 μ T, while in the BAL curve there is a maximum at around 1600 AD with values up to 50 μ T. This might be a hint that it is a local geomagnetic field feature. Following the recent study of Donadini et al 15. directional features of Africa coincide with those from Europe.…”

Section: Discussionmentioning

confidence: 75%

“…Each block sample was cut in cubes of 2 cm side length. In order to determine the rock magnetic properties Donadini et al 15. performed measurements of thermomagnetic curves (magnetic susceptibility versus temperature), hystereses, backfield curves, and 3-axes Isothermal Remanent Magnetization (3IRM) curves.…”

Section: Methodsmentioning

confidence: 99%

“…Up to now, data from Africa is still too sparse to infer if such field features randomly appeared at different locations or moved around. Nevertheless, some studies observe similarities of field behavior between Africa and Europe101115. Field features observed by or inferred from satellite data, such as the South Atlantic Anomaly (SAA), an area of low magnetic field strength, which spans the southern Atlantic Ocean, or equatorial flux spots, which are regions at the surface of the liquid core with unusually large intensity, are hardly brought into context with archaeomagnetic data.…”

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confidence: 99%

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Reconstructing the Geomagnetic Field in West Africa: First Absolute Intensity Results from Burkina Faso

Kapper

Donadini

Serneels

et al. 2017

Sci Rep

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We present absolute geomagnetic intensities from iron smelting furnaces discovered at the metallurgical site of Korsimoro, Burkina Faso. Up to now, archaeologists recognized four different types of furnaces based on different construction methods, which were related to four subsequent time periods. Additionally, radiocarbon ages obtained from charcoal confine the studied furnaces to ages ranging from 700–1700 AD, in good agreement with the archaeologically determined time periods for each type of furnace. Archaeointensity results reveal three main groups of Arai diagrams. The first two groups contain specimens with either linear Arai diagrams, or slightly curved diagrams or two phases of magnetization. The third group encompasses specimens with strong zigzag or curvature in their Arai diagrams. Specimens of the first two groups were accepted after applying selection criteria to guarantee the high quality of the results. Our data compared to palaeosecular variation curves show a similar decreasing trend between 900–1500 AD. However, they reveal larger amplitudes at around 800 AD and 1650 AD than the reference curves and geomagnetic field models. Furthermore, they agree well with archaeomagnetic data from Mali and Senegal around 800 AD and with volcanic data around 1700 AD.

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Section: Archaeointensity Resultsmentioning

confidence: 66%

Section: Discussionmentioning

confidence: 75%

Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

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Reconstructing the Geomagnetic Field in West Africa: First Absolute Intensity Results from Burkina Faso

Kapper

Donadini

Serneels

et al. 2017

Sci Rep

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“…Archaeomagnetic data were obtained from several furnaces [13]. The preliminary archaeometallurgical investigations on slag and related materials were performed at the University of Fribourg (geochemistry by XRF, mineralogy by XRD, and optical and electronic microscopy on thin polished sections [14]).…”

Section: Investigation Strategymentioning

confidence: 99%

The massive production of iron in the Sahelian belt: Archaeological investigations at Korsimoro (Sanmatenga – Burkina Faso)

Serneels

2016

Materials and Manufacturing Processes

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The large smelting site of Korsimoro was investigated during two fieldwork campaigns in 2011 and 2012. Four different technical traditions are identified. Each is characterized by the spatial organization of the working area, the architecture of the furnace, and the assemblages of wastes. Each technical tradition corresponds to one chronological phase. Phase KRS 1 lasted between 600 and 1000 AD and is characterized by small-scale production. Phases KRS 2 and 3, between 1000 and 1450 AD, showed a very significant increase of the production with an important impact on the organization of the society. There is a collapse of the industry at the time of the installation of the Nakomse conquerors followed by a recovery of the production at a small scale during the 17th century.

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Epsilon iron oxide: Origin of the high coercivity stable low Curie temperature magnetic phase found in heated archeological materials

López-Sánchez

McIntosh

Osete

et al. 2017

Geochem Geophys Geosyst

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The identification of epsilon iron oxide (ɛ‐Fe2O3) as the low Curie temperature high coercivity stable phase (HCSLT) carrying the remanence in heated archeological samples has been achieved in samples from two archeological sites that exhibited the clearest evidence of the presence of the HCSLT. This uncommon iron oxide has been detected by Confocal Raman Spectroscopy (CRS) and characterized by rock magnetic measurements. Large numbers of ɛ‐Fe2O3 microaggregates (in CO) or isolated clusters (in HEL) could be recognized, distributed over the whole sample, and embedded within the ceramic matrix, along with hematite and pseudobrookite and with minor amounts of anatase, rutile, and maghemite. Curie temperature estimates of around 170°C for CO and 190°C for HEL are lower than for pure, synthetic ɛ‐Fe2O3 (227°C). This, together with structural differences between the Raman spectra of the archeologically derived and synthetic samples, is likely due to Ti substitution in the ɛ‐Fe2O3 crystal lattice. The γ‐Fe2O3‐ɛ‐Fe2O3‐α‐Fe2O3 transformation series has been recognized in heated archeological samples, which may have implications in terms of their thermal history and in the factors that govern the formation of ɛ‐Fe2O3.

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Directional changes of the geomagnetic field in West Africa: Insights from the metallurgical site of Korsimoro

Cited by 13 publications

References 30 publications

Reconstructing the Geomagnetic Field in West Africa: First Absolute Intensity Results from Burkina Faso

Reconstructing the Geomagnetic Field in West Africa: First Absolute Intensity Results from Burkina Faso

The massive production of iron in the Sahelian belt: Archaeological investigations at Korsimoro (Sanmatenga – Burkina Faso)

Epsilon iron oxide: Origin of the high coercivity stable low Curie temperature magnetic phase found in heated archeological materials

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