Along the base of the Brenner Mesozoic (Central Alps, Austria), the topmost part of the Oetztal-Stubai crystalline complex displays a zone of Fe- and Al-rich phyllitic schists. Field relations and geochemical and mineralogical data suggest that this zone is a paleo-weathering horizon, which was overprinted at higher greenschist grade during Alpidic regional metamorphism. Considering the overlying elastic sedimentary rocks and the mode of occurrence, a hydrothermal-metasomatic origin of the alteration zone can be excluded. Dating of the basement uplift and event-stratigraphic correlations of the overlying elastic rocks with unmetamorphosed sedimentary rocks of the Northern and Southern Alps imply a middle to late Scythian age (Early Triassic) of the weathering. A combination of structural, petrographic, and stratigraphic data to correlate such horizons, especially in metamorphic terranes, is necessary for reconstructing the paleoenvironment and solving tectonic problems.

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