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Could be cool but who knows without a key to read it.
Is there a key?
- Map key (and split map copy): “Back Matter” PDF (19 MB) from the map + article at geoscienceworld.org
- Text explanation in article without map at USGS.gov (see page 7 of 28)
Unfortunately, I cannot find a non-rasterized digital version even though the original clearly was a digitally typeset document.
