0 thoughts on “Friday fold: Chert chunk”

  1. I really like your Friday fold series- awesome stuff!
    However, here with a chert piece, I agree on the fault, but I question the fold!
    Particularly without any locale data, this looks to be a common nodule of chert with banded/zoned coloration relative to its diagenesis. Probably from a bedded deposit with a nodular inclusion or zone. You are looking at a partial cross section, freshly cleaved. It’s natural placement would have been horizontal, not vertical. You can see the ‘left’ dark zone coming back ‘in’ to the nodules thinning edge at the ‘bottom’ of your vertical picture.
    I never say never, but I strongly doubt you would get a sharp clean angle like that out of a folded chert bed or nodule without brecciation first(and probable reheal apparent from after.) Just curious, take another look and see what you think!?
    Best,
    JohnO:

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