Palynomorphe und organisches Material aus den Raibler Schichten einer oberostalpinen Schuppe der Iberger Klippen (Kanton Schwyz, Schweiz)

A palynology and organic matter study has been carried out on samples of the Upper Triassic Raibl beds from an Upper Austroalpine thrust sheet, preserved in the area of the Iberg Klippen (Laucherenst?ckli). The palynological assemblages indicate an early Carnian (Julian) age. Comparison with well calibrated successions from the Southern Alps suggests a correlation with the Late Julian ammonoid zone Austrotrachyceras austriacum. The lithofacies of the studied sections suggests a substantial similarity to Raibl beds of the Upper Austroalpine of the Northern Calcareous Alps and those of the Silvretta- and the S-charl nappe of the Grisons. The minute Upper Austroalpine thrust sheet represents the westward extension of series with similar facies, which are still preserved in the Northern Calcareous Alps of Liechtenstein and western Austria (Vorarlberg). According to the Thermal Alteration Scale (TAS) of Batten (1996) the observed medium brown colors of the pollen grains correspond to a value of 4/5, which is equivalent to vitrinite reflectance (VR) values of 0.7–0.9 %R_o. In comparison with other sites in Liechtenstein, Vorarlberg and the Upper Austroalpine of Central Grisons (Silvretta and S-charl nappe) with measured VR values of > 2%R_o the organic matter of the studied samples shows only minor thermal alteration, indicating that the Upper Austroalpine thrust sheets of Iberg represent the highest part of the nappe stack in Central Switzerland, formerly covered by a comparatively thin overburden.