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Western Piedmont Metasedimentary Rocks

The information contained on this page was adapted from Maryland Geological Survey's Geologic Map of Maryland (1968). This information reflects geologic interpretations from over 20 years ago and do not necessarily represent an accurate interpretation of currently accepted geologic theory. We present this information for historic purposes only. Do not use this information for anything other than illustrative purposes. When a corrected and updated geologic map of Maryland is available you will see a notification on our web site.

Late Precambrian (?) Urbana Formation (Late Precambrian ?) Urbana Formation
Dark gray to green sericite-chlorite phyllite, metasiltstone, and quartzite; thin lenses of impure marble and calcareous phyllite occur locally.
Sugarloaf Mountain Quartzite (Late Precambrian ?)
Sugarloaf Mountain Quartzite
Massive white quartzite interbedded with softer sericitic quartzite, slate, and phyllite.
Libertytown Metarhyolite (Late Precambrian ?) Libertytown Metarhyolite
Purple, bluish-black and red, dense, fine-grained metarhyolite with feldspar phenochrysts; interbedded with blue and purple amygdaloidal metaandesite; both rhyolite and andesite interbedded with blue, purple, and green phyllitic slates.
Sams Creek Metabasalt (Late Precambrian ?) Sams Creek Metabasalt
Grayish-green, massive to schistose, amygdaloidal metabasalt.
Wakefield Marble (Late Precambrian ?) Wakefield Marble
White, fine-grained marble; subordinate white, green, and pink variegated marble; and blue marble.
Silver Run Limestone (Late Precambrian ?) Silver Run Limestone
Blue, thin-bedded, finely crystalline schistose limestone and calcareous slate.
Ijamville Formation / Marburg Schist (Late Precambrian ?) Ijamville Formation (Late Precambrian ?) Ijamville Formation
Blue, green, or purple phyllite and phyllitic slate, with interbedded metasiltstone and metagraywacke; flattened pumiceous blebs occur locally.
Marburg Schist (Late Precambrian ?) Marburg Schist
Bluish-gray to silvery-green, fine-grained, muscovite-chlorite-albite-quartz schist; intensely cleaved and closely folded; contains interbedded quartzites.
Wissahickon Formation (Late Precambrian ?)

Wissahickon Formation
Muscovite-chlorite schist, chloritoid schist, and quartzite; intensely folded and cleaved.

Please note the changes in the former "Wissahickon formation" nomenclature that are presented on the Eastern Piedmont Metasedimentary Rocks page.

Updated 8/29/00

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