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These data were generated to determine the anthropogenic hematite grains
resulted from ochre processing at the Xiamabei site in the Nihewan Basin,
northern China. Four samples were selected for sediment analyses,
including Raman spectroscopy, X-ray diffraction (XRD), high-temperature
magnetic susceptibilities, and/or magnetic component analysis of
coercivity distributions. Two sediment samples (X1 and X2) come from the
red stained area on which the ochre fragments OP1 and OP2, stone slab LS
and quartzite cobble QC were found; two samples (X3 and X6) were retrieved
in the same layer but at ~2 m distance from the stained area. All of the
samples consist of flood plain silts. The Raman spectra unambiguously
identify hematite in red particles abundantly present in samples X1 and
X2. The XRD measurements clearly show that hematite is abundant in samples
X1 and X2. However, hematite is not detectable in samples X3 and X6. The
volume percent for hematite is 0.9% in sample X1 and 1.7% in sample X2.
The high-temperature magnetic susceptibility measurements suggest that
hematite dominates the magnetic mineralogy of samples X1 and X2. Magnetic
component analyses of coercivity distributions show distinct assemblages
of magnetic minerals in samples X1 and X2, which have three components
with low, middle and high coercivities. The low-coercivity component with
median acquisition field of 40-62 mini Tesla (mT) is interpreted as
magnetite and/or maghemite. The middle-coercivity component with median
acquisition field of 100-166 mT is interpreted as partially-oxidized
coarse-grained magnetite. The high-coercivity component with median
acquisition field of up to 575 mT is interpreted as single domain
hematite, because the single domain threshold grain size of hematite is
considerably larger than 15 micrometers, and even up to 100 micrometers.
This kind of hematite grains with high coercivities up to several hundreds
of mT is usually of detrital origin, and is documented as evidence for the
earliest ochre processing in east Asia. The new findings provide new
insights into the expansion of Homo sapiens.
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