TY - JOUR
T1 - Implications from chemical, structural and mineralogical studies of magnetic microspherules from around the lower younger dryas boundary (New Mexico, USA)
AU - Andronikov, Alexandre V.
AU - Andronikova, Irina E.
AU - Loehn, Clayton W.
AU - Lafuente, Barbara
AU - Ballenger, Jesse A.M.
AU - Crawford, George T.
AU - Lauretta, Dante S.
N1 - Publisher Copyright:
© 2016 Swedish Society for Anthropology and Geography.
PY - 2016/3/1
Y1 - 2016/3/1
N2 - Hollow magnetic microspherules from along the lower Younger Dryas boundary (c. 12.9 ka bp) in New Mexico (USA) were studied using scanning electron microscopy, electron probe microanalysis, X-ray diffraction, and laser-ablation inductively coupled-plasma mass spectrometry methods. The shell of the microspherules (10-15% of the spherule's diameter) displays dendritic surface textures, which are likely due to quenching during rapid cooling of molten material. Structurally, multiple single-magnetite crystals attached together form the bulk of the microspherules. Iron dominates the microspherules' composition (∼90% FeOtot), Mn is the second most abundant element (up to 0.4% MnO), Al is detected in low concentrations (<0.30% of Al2O3). Among the trace elements, the rare earth elements display slightly fractionated patterns with concentrations of 0.1-1.0× CI chondrite. The microspherules contain elevated concentrations of Ni relative to detrital magnetite (up to 435 ppm) and very low concentrations of Ti (down to 5 ppm). Chemical, structural and mineralogical features of the microspherules do not contradict the existing models of the formation during ablation while a meteoroid goes through the Earth's atmosphere. Elevated concentrations of the magnetic microspherules in sediments can be a stratigraphic marker for the lower Younger Dryas boundary in North America.
AB - Hollow magnetic microspherules from along the lower Younger Dryas boundary (c. 12.9 ka bp) in New Mexico (USA) were studied using scanning electron microscopy, electron probe microanalysis, X-ray diffraction, and laser-ablation inductively coupled-plasma mass spectrometry methods. The shell of the microspherules (10-15% of the spherule's diameter) displays dendritic surface textures, which are likely due to quenching during rapid cooling of molten material. Structurally, multiple single-magnetite crystals attached together form the bulk of the microspherules. Iron dominates the microspherules' composition (∼90% FeOtot), Mn is the second most abundant element (up to 0.4% MnO), Al is detected in low concentrations (<0.30% of Al2O3). Among the trace elements, the rare earth elements display slightly fractionated patterns with concentrations of 0.1-1.0× CI chondrite. The microspherules contain elevated concentrations of Ni relative to detrital magnetite (up to 435 ppm) and very low concentrations of Ti (down to 5 ppm). Chemical, structural and mineralogical features of the microspherules do not contradict the existing models of the formation during ablation while a meteoroid goes through the Earth's atmosphere. Elevated concentrations of the magnetic microspherules in sediments can be a stratigraphic marker for the lower Younger Dryas boundary in North America.
KW - Magnetic microspherules
KW - Trace elements
KW - Younger dryas
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U2 - 10.1111/geoa.12122
DO - 10.1111/geoa.12122
M3 - Article
AN - SCOPUS:84959432198
VL - 98
SP - 39
EP - 59
JO - Geografiska Annaler, Series A: Physical Geography
JF - Geografiska Annaler, Series A: Physical Geography
SN - 0435-3676
IS - 1
ER -