RUSSIAN JOURNAL OF EARTH SCIENCES VOL. 8, ES3001, doi:10.2205/2006ES000204, 2006
[6] The general geological position of the section in the Gams area was previously defined by Lahodynsky [1988], who established that the section belongs to the Nierntal Formation (magnetochron C29r). Sediments of the formation are weakly lithified and undeformed and lie monoclinally. The part of the section below the K/T transition layer is represented by alternating calcareous marl and marly limestone; clays with various concentrations of calcium carbonate are mostly developed above the transition clay layer. The latter is enriched in the smectite component and is characterized by higher concentrations of Ir (up to 10 ppb), Cr, Co, Ni, MgO, Al2O3, and TiO2 [Lahodynsky, 1988].
[7] The section, represented in a monolith, is divided into three parts (Figure 1): the lower light gray carbonate part (beds A-I) overlain by the transition layer J on which a lens of gray clayey marl (K) rests. The upper part is represented by clays and siltstones colored dark gray to black (layers L-W). Light gray sand interbeds S and T enriched in terrigenous material, primarily quartz, are observed in the upper part of the section. According to such components as SiO2, Al2O3, CaO, Fe2O3, and K2O, the section is divided into the same parts. The lower part (layers A-I) is characterized by low concentrations of silica, alumina, iron, and potassium and by high calcium concentrations. In the middle part (the transition layer J), the concentrations of silica, alumina, iron, and potassium drastically increase, whereas the Ca and Mn concentrations significantly decrease. By the concentrations of silica, iron, calcium, sodium, and potassium, the layer K transitional to the upper part of the section is intermediate between the Maestrichtian and Danian deposits. The upper part of the section (layers L-W) are characterized by insignificant variations in the bulk composition. An exception is the layers S and T enriched in SiO2 and depleted in iron and aluminum.
[8] It is noteworthy that the terrigenous component sharply increases in the upper part of the section: the fraction of normative quartz and feldspathoids above the layer J rises to 40-70%, whereas it varies weakly and amounts to about 10% in the lower part of the section.
[9] A relatively homogeneous ensemble of clays dominated by smectite (37-62%) and illite (29-45%) is typical of the section. Against this background, the lens K is specific because the concentration of illite is 70.5%, which may be related to stronger denudation in the source area because this mineral usually forms due to erosion of crystalline rocks.
Citation: 2006), Magnetolithologic and Magnetomineralogical Characteristics of Deposits at the Mesozoic/Cenozoic Boundary: Gams Section (Austria), Russ. J. Earth Sci., 8, ES3001, doi:10.2205/2006ES000204.
Copyright 2006 by the Russian Journal of Earth Sciences (Powered by TeXWeb (Win32, v.2.0).