RUSSIAN JOURNAL OF EARTH SCIENCES VOL. 7, ES6001, doi:10.2205/2005ES000189, 2005
[17] The general setting of the stratigraphic sequence in the Gams area (Knappengraben) was characterized by Lahodynsky [1988], who determined that it belonged to the Nierental Formation (chron 29R). The part of the sequence below the transitional layer at the K/T boundary consists of alternating calcareous marlstone and marly limestone, and the transitional clay layer is overlain by a clay-dominated unit with variable proportions of Ca carbonate and occasional sandstone-siltstone intercalations. The transitional clay layer at the K/T boundary is enriched in smectite and has elevated concentrations of Ir (up to 10 ppb), Cr, Co, Ni, MgO, Al2O3, and TiO2 [Lahodynsky, 1988]. The aforementioned paper presents no data on the faunal characteristics of the layer, neither does it describe any factual materials on the major- and trace-element chemistry concentrations or information on the analytical techniques.
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[19] According to the decision of the International Union of Geological Sciences, the boundary between the Cretaceous and Paleogene, or the lower boundary of the Danian stage of the Paleogene is determined by the Ir anomaly proximal to the mass extinction of typical Cretaceous faunal groups (foraminifers, nannoplankton, dinosaurs, etc.). The global stratotype of this boundary (GSSP) was chosen to be the El-Kef sequence in Tunisia "In the El-Haria section near El-Kef, Tunisia, at the base of the boundary clay" [Cowie et al., 1989].
[20] In compliance with this, we drew the Cretaceous- Paleogene boundary in the Gams sequence in the Alps, Austria, through the middle part of clayey layer J, which is enriched in Ir, rests immediately on marls and clayey limestone, and bears a wealth of typically Cretaceous planktonic foraminifers. The layer lies in the upper part of Nierental Formation of the Gosau Group [Kollmann, 1964], which consists of a thick unit of predominantly clayey limestone, marl, and siltstone. The layer separates the lower (predominantly calc-marly) and upper (predominantly silty-clayey) parts of the Gosau Formation or occurs near the roof of the lower portion of the Gosau Formation (Lower Gosau) [Peryt et al., 1993; Preisinger et al., 1986].
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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