The Greywacke Zone

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Photo of gently folded Schwarzphyllites (black phyllites) with primary quartzite layers. The Schwarzphyllites originated from dark, clayey sediments of an ocean basin. The dark color is attributed to organic components (dead plants or microorganisms). The quartzites were originally quartz sandstones, transported from the beach area to the sea by rivers or currents, suggesting a sedimentary environment that was likely near the coast.

The detailed sketch (location as seen in the photo) illustrates the relationship between bedding, foliation, and partially folded quartz mobilized by melting. The most recent deformation consists of extensional fractures, mostly open, with some fractures healed by quartz (which requires temperatures above 300°C).