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Geosciences LibreTexts

5.1: Geologic Map

  • Page ID
    11138
  • Map

    This is the map of the area (without annotations):click on the image to enlarge.

    Here is an annotated map of the area, showing approximate sample locations and towns, as well as the Fries Fault and major structural units:

    Rock Units

    Formation Age Sample # Rock Type Protolith
    Ashe Formation Protolith Age: 600 Ma (Late Proterozoic). Age of metamorphism: 450-430 Ma. A1 B2, A3 schist Staurolite Schist (Pelite) Fine-grained mudstone
    A1 amph, A3 Amph Amphibolite Basalt or Gabbro
    UM1 Soapstone / serpentinite Ultramafic (peridotite)
    Fries Fault Zone Fault Age To Be Determined A4 Mylonite 1 Mylonite Cranberry Gneiss
    A4 Mylonite 2 Mylonite Ultramafic or mafic protolith
    Cranberry Gneiss Protolith Age: ~1.1 Ga (billion years) Age of metamorphism: gneissic fabric – 900 Ma? faulting age is unknown. Cranberry Orthogneiss Granite
    S5 Cranberry Paragneiss Sedimentary
    Striped Rock Granite Crystallization age ~690 Ma. Perhaps associated with Mt Rogers volcanics (~750 Ma)? S6 Striped Rock Granite Not applicable
    Unicoi Formation Early Cambrian (like the Chilhowee Group near JMU) Unicoi 1 Shale / mudstone Not applicable
    Unicoi 2 Greenstone Basalt
    Unicoi 3 Conglomerate Not applicable

    Field Bulletin

    The map and field descriptions of this area (by Stose and Stose) are available here: https://www.dmme.virginia.gov/commercedocs/BUL_72.pdf

    And from this page (it is free to download, even though it is the DMME “store”): https://www.dmme.virginia.gov/commerce/ProductDetails.aspx?productID=2272

    Like most map bulletins, the text is first, and the maps are at the very end of the .pdf document.