Greywacke Zone - Folded Phyllites and Quartzite

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Folded dark phyllites and quartzites and/or acidic metavolcanics

The Schwarzphyllites originated from dark, clayey sediments of the deep sea. The dark, sometimes reddish color is due to often-present organic components and iron compounds. However, none of the original clay minerals remain. The current mineral composition is characterized by metamorphism (rock transformation) during a mountain-building process under extreme conditions (temperature ≈ 350°C - 550°C, pressure ≈ 200 - 1000 MPa), resulting in mica, quartz, sometimes feldspar, chlorite, and iron oxide.

The detailed sketch illustrates the relationship between the original bedding, the initial foliation, and the second foliation in the form of axial plane foliation. Refer to the photo for the sketch‘s location.

The light, compact layers were originally either quartz sandstones, transported from the beach area to the sea by rivers or currents, indicating a sedimentary environment that was likely near the coast. Alternatively, they could be volcanic tuffs, suggesting active volcanism during the deposition of the clayey sediments.