Two spinel populations from the Cretaceous-Paleogene (K/T) boundary clay layer in the Gams stratigraphic sequence, Eastern Alps

¹Schmidt Institute of Physics of the Earth, Russian Academy of Sciences, Moscow, Russia
²Geophysical Observatory, Schmidt Institute of Physics of the Earth, Russian Academy of Sciences, Borok, Yaroslavl oblast, Russia
³Geological Institute, Russian Academy of Sciences, Moscow, Russia
⁴Museum of Natural History, Vienna, Austria

Abstract

[1]  The K/T boundary layer in the Gams stratigraphic sequence, Eastern Alps, was determined to contain two spinel populations. One of them is dominated by Cr spinel, which originated from eroded high-pressure metamorphic rocks of eclogite composition, which are widespread in the Eastern Alps. This spinel is not only typical of the whole K/T boundary layer but was also found farther upsection in Maestrichtian clay. The other spinel population principally differs from the first one in having high Ni concentrations. Ni spinel from the Gams section differs by the high content of zinc (up to 5.6% in a rust crust), that is not characteristic for other known sections at the K/T boundary. Alongside with well expressed crystals octahedral forms, one grain of drop-like mode of Ni spinel has been found. It is considered, that Ni spinel is confined to 1-3 mm rust colored layer which has deposited in less than 100 years, while in the Gams section it meets in all parts of the transition layer. The question of origin Ni spinel from the transitional layer at the K/T boundary remains opened and demands the further researches.

Received 21 September 2007; accepted 9 November 2007; published 20 November 2007.

Keywords: K/T boundary, spinel, impact, Eastern Alps.

Index Terms: 1051 Geochemistry: Sedimentary geochemistry; 1519 Geomagnetism and Paleomagnetism: Magnetic mineralogy and petrology; 3665 Mineralogy and Petrology: Mineral occurrences and deposits; 5420 Planetary Sciences: Solid Surface Planets: Impact phenomena, cratering.

Citation: Grachev, A. F., V. A. Tselmovich, O. A. Korchagin, and H. A. Kollmann (2007), Two spinel populations from the Cretaceous-Paleogene (K/T) boundary clay layer in the Gams stratigraphic sequence, Eastern Alps, Russ. J. Earth Sci., 9, ES2002, doi:10.2205/2007ES000297.