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National Geologic Map Database
Map showing publication footprint
  • Usage in publication:
    • Rush Brook Member
  • Modifications:
    • Named
  • Dominant lithology:
    • Gneiss
    • Schist
  • AAPG geologic province:
    • Piedmont-Blue Ridge province
Publication:

Crowley, W.P., 1976, The geology of the crystalline rocks near Baltimore and its bearing on the evolution of the eastern Maryland Piedmont: Maryland Geological Survey Report of Investigations, no. 27, 40 p.


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.

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