RUSSIAN JOURNAL OF EARTH SCIENCES VOL. 7, ES6001, doi:10.2205/2005ES000189, 2005
[72] Tables 8 and 9 report the distribution of the concentrations of trace elements and REE in the vertical section of the sequence, and Table 10 presents the contents of Ir and some other chalcophile elements in transitional layer J at the K/T boundary. The variations of the most informative elements (lithophile Cr, V, Rb, Cs, Ba, Sr, Nb, and Zr; chalcophile Cu, Zn, and Ga; and siderophile Co, Ni, and Mo) are the most dramatic and mutually correlated in the vicinity of transitional layer J.
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Figure 19 |
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Figure 20 |
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Figure 21 |
[75] Since layer J is of particular interest, it was subdivided into a number of units (Figure 4) in order to determine how concentrations of Ir and other elements vary from the bottom to top of this layer. It was revealed that the Ir concentration drastically increases from 5 ppm to 9 ppm upward (from J1 to J4 ) and then drops to 3 ppb at J5-J6 (Table 10). The contents of As, Pb, Ag, Au, and Br also change in the same units (Figure 20).
[76] In contrast to trace elements, variations in the concentrations of REE in the Gams sequence are insignificant (Table 10). In a few samples, REE were analyzed in their whole-rock material and clay fractions. The REE concentration in sample L6 is systematically higher in the clay fraction than in the whole-rock sample.
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Figure 23 |
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Figure 24 |
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Figure 25 |
[78] This flat configuration of the NASC-normalized REE patterns is typical of the rocks of Mesozoic and Cenozoic continental margins (including those in the modern Atlantic) [Murray, 1994] and testify to a significant contribution of terrigenous material to the character of REE fractionation. In this context, the similarities in the REE patterns of rocks from the examined portion of the Gams sequence suggest that the conditions in the source area (which was not far from the marine basin) did not vary.
Citation: 2005), A new look at the nature of the transitional layer at the K/T boundary near Gams, Eastern Alps, Austria, and the problem of the mass extinction of the biota, Russ. J. Earth Sci., 7, ES6001, doi:10.2205/2005ES000189.
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