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Juniata Formation

Juniata Formation - Red to greenish-gray, thin- to thick-bedded siltstone, shale, subgraywacke, and protoquartzite; interbedded conglomerate; thickness 180 feet in east, increases to 500 feet in west.
StateMaryland
NameJuniata Formation
Geologic ageOrdovician
Original map labelOj
Commentssecondary lithologic description from USGS Geologic Names lexicon (ref. MD005): Juniata can be divided into three informal units: a lower red sandstone, a middle red siltstone and shale, and an upper quartzitic sandstone. [Members of Swartz, 1957, not used.] Lower sandstone is a fine-grained graywacke, slightly argillaceous in places. Middle sequence is grayish-red shale and silty shale with some interbeds of thick-bedded, very fine grained sandstone. Upper sandstone is generally upward-coarsening red shale, silty shale, siltstone, and sandstone.
Primary rock typesandstone
Secondary rock typeshale
Other rock typesgraywacke; siltstone; conglomerate
Lithologic constituents
Major
Sedimentary > Clastic > Sandstone
Minor
Sedimentary > Clastic > Sandstone > Graywacke
Sedimentary > Clastic > Mudstone > Shale
Sedimentary > Clastic > Siltstone
Incidental
Sedimentary > Clastic > Conglomerate
Map references
Cleaves, E.T., Edwards, J., Jr., Glaser, J.D., 1968, Geologic Map of Maryland: Maryland Geological Survey, Baltimore, Maryland, scale 1:250,000.
Unit references
Cleaves, E.T., Edwards, J., Jr., Glaser, J.D., 1968, Geologic Map of Maryland: Maryland Geological Survey, Baltimore, Maryland, scale 1:250,000.
Unpublished digital version of the Maryland state geologic map that was digitized by the USGS Water Resources Office in Towson, MD
Geographic coverageAllegany - Washington

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