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McAvoy's VA & NC Orhoquartzite Survey

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  • McAvoy's VA & NC Orhoquartzite Survey

    The link below is to McAvoy's (Cactus Hill site investigator) orthoquartzite survey, (4 meg). I've been searching for possible quarries in Maryland that match the material that he names Stafford, without ever finding an exact match. The Stafford OQ has a cream colored matrix with almost all angular grains and pebble chips. Based on the amount of angular grains in its make-up, I'm betting it is named appropriately, and that its source will be found in the vicinity of Frederickburgs, VA , with all of the geologic faults running through there. Note that the shell fragment shown in his #36 looks like a base to an Ecphora snail, if so it would limit the source to being Miocene or Pliocene in age, I think.
    https://img1.wsimg.com/blobby/go/a9f...32955467%C2%A0
    Coastal Plain of Maryland

  • #2
    Interesting read. Possibly related:

    https://www.dhr.virginia.gov/lithics/oolitic-quartzite/

    https://www.dhr.virginia.gov/lithics...rthoquartzite/
    Central Virginia

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    • #3
      QKeith, thanks for the input. I think that both are related; with the "Oolitic" Quartzite being the same as the Stafford named material.
      Click image for larger version

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      MD Paleocene OQ on right with lots of glauconite
      The Aquia orthoquartzite over here is loaded with glauconite making it a mismatch for the most part. That Virginia Aquia OQ has always looked to have "thicker" opaline matrix without the glauconite in pictures though. Wanted to try to find, and get a look at the outcrop but Covid put a damper on it.

      Virginia does a great job with their lithics and points page, where else could you see Fort Nottaways or all of those regional cherts and jaspers.

      Coastal Plain of Maryland

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