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- Usage in publication:
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- Rush Brook Member
- Modifications:
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- Named
- Dominant lithology:
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- Gneiss
- Schist
- AAPG geologic province:
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- Piedmont-Blue Ridge province
Summary:
Name Rush Brook Member of Loch Raven Schist (new) is proposed for quartz-rich gneiss and schist that outcrop along Rush Brook in Baltimore Co., MD. The member is heterogeneous, but generally quartz-rich and fine-grained. Most typical rock types are interlayered biotite-feldspar-quartz gneiss, biotite-feldspar quartz schist, and muscovite-biotite-feldspar-quartz schist. Interlayered medium-grained quartzites are locally important. Unit also contains amphibolite and marble. Tourmaline is common accessory mineral in schist-quartzite assemblage. Thickness ranges from 0 to 600 m. Overlies Cockeysville Marble; underlies main body of Loch Raven Schist of Wissahickon Group. Age of entire Wissahickon is given as Cambrian-Ordovician(?).
Source: GNU records (USGS DDS-6; Reston GNULEX).
For more information, please contact Nancy Stamm, Geologic Names Committee Secretary.
Asterisk (*) indicates published by U.S. Geological Survey authors.
"No current usage" (†) implies that a name has been abandoned or has fallen into disuse. Former usage and, if known, replacement name given in parentheses ( ).
Slash (/) indicates name conflicts with nomenclatural guidelines (CSN, 1933; ACSN, 1961, 1970; NACSN, 1983, 2005, 2021). May be explained within brackets ([ ]).