Geologic Map Legends
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.

		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 Massive white quartzite interbedded with softer sericitic quartzite, slate, and phyllite.
		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 Grayish-green, massive to schistose, amygdaloidal metabasalt.
		Wakefield Marble White, fine-grained marble; subordinate white, green, and pink variegated marble; and blue marble.
		Silver Run Limestone Blue, thin-bedded, finely crystalline schistose limestone and calcareous slate.
			Ijamville Formation Blue, green, or purple phyllite and phyllitic slate, with interbedded metasiltstone and metagraywacke; flattened pumiceous blebs occur locally.
			Marburg Schist Bluish-gray to silvery-green, fine-grained, muscovite-chlorite-albite-quartz schist; intensely cleaved and closely folded; contains interbedded quartzites.
		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.