RUSSIAN JOURNAL OF EARTH SCIENCES VOL. 10, ES6006, doi:10.2205/2008ES000304, 2008
[8] Let us consider the behavior of iron over an interval of hundred of thousand - few million of years around the K/T boundary. Within each section (that is through the time), the concentration of iron varies from zero to 0.002% in the Gams section and to 0.004% in the Teplovka section; its concentration does not exceed 0.0002% in the Tetritskaro and Koshak sections (Figure 4). Note that the maximums of this parameter are found at different levels and are not coeval. Hence the enrichment by metallic iron was not synchronous. Besides, a certain lithological control appears to exist as higher iron concentrations are found in Danian terrigenous sediments of the Gams section, while the lowest ones are from carbonaceous sediments of the Tetritskaro and Koshak sections. On the other hand, the samples where iron is absent are more common in terrigenous sediments; first of all, it is true for the boundary layer.
[9] Thus very high non-uniformity in distribution of metallic iron in both space and time appears to be present. This may be accounted for in three different ways: "primary extraterrestrial'' due of accumulation of metallic iron particles both from cosmic dust and from ablation of meteorites; "primary terrestrial'' due of accumulation of metallic iron particles of terrestrial origin; and "secondary'' as a result of subsequent oxidation of metallic iron particles with formation of Fe-hydroxides and hematite. Large variation in concentration of metallic iron in sediments is not compatible with steady influx of cosmic dust to the Earth surface. First and foremost, I connect this variation with different amount of information; also, the concentration of metallic iron in cosmic dust is low, and its distribution is not necessarily proportional to the total influx of the dust. Besides, it is possible that the main source of metallic iron is meteorite falls and not the cosmic dust.
Citation: 2008), Metallic iron in sediments at the Mesozoic-Cenozoic (K/T) boundary, Russ. J. Earth Sci., 10, ES6006, doi:10.2205/2008ES000304.
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