U.S. Geological Survey Home AASG Logo USGS HOME CONTACT USGS SEARCH USGS
National Geologic Map Database
Geologic Unit: Oella
Map showing publication footprint
  • Usage in publication:
    • Oella Formation
  • Modifications:
    • Named
  • Dominant lithology:
    • Schist
    • Gneiss
  • 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:

Oella Formation of Wissahickon Group named for town of Oella in southwestern Baltimore Co., MD. Consists of biotite-plagioclase-muscovite quartz schist, interlayered with biotite-plagioclase-quartz gneiss and, locally, epidote amphibolite. Thickness ranges to 1,300 m. Locally divisible into a lower unnamed metasedimentary unit, and upper Sweathouse Amphibolite Member. Overlies Loch Raven Schist and underlies Sykesville Formation. Age is Cambrian-Ordovician(?).

Source: GNU records (USGS DDS-6; Reston GNULEX).


Map showing publication footprint
  • Usage in publication:
    • Oella Formation
  • Modifications:
    • Revised
  • AAPG geologic province:
    • Piedmont-Blue Ridge province
Publication:

Muller, P.D., Candela, P.A., and Wylie, A.G., 1989, Liberty Complex; polygenetic melange in the central Maryland Piedmont, IN Horton, J.W., Jr., and Rast, Nicholas, eds., Melanges and olistostromes of the U.S. Appalachians: Geological Society of America Special Paper, 228, p. 113-134.


Summary:

Field and map relations suggest that Loch Raven Schist and Oella Formation are different lithofacies within same stratigraphic interval rather than two distinct stratigraphic units.

Source: GNU records (USGS DDS-6; Reston GNULEX).


Map showing publication footprint
  • Usage in publication:
    • Oella
  • Modifications:
    • Not used
  • AAPG geologic province:
    • Piedmont-Blue Ridge province
Publication:

Gates, A.E., Muller, P.D., and Valentino, D.W., 1991, Terranes and tectonics of the Maryland and southeast Pennsylvania Piedmont, IN Schultz, Art, and Compton-Gooding, Ellen, eds., Geologic evolution of the eastern United States; Field trip guidebook NE-SE GSA 1991: Virginia Museum of Natural History Guidebook, Joint meeting of Geological Society of America, Northeastern Section and Southeastern Section, no. 2, p. 1-27.


Summary:

Loch Raven Formation is described in this report as consisting of two dominant lithologies: 1) a medium to coarse-grained mica schist and 2) a medium-grained gneiss formerly referred to as Oella Formation by Crowley (1976).

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 ([ ]).

Accessibility FOIA Privacy Policies and Notices

USA Gov U.S. Department of the Interior | U.S. Geological Survey
Supported by the National Cooperative Geologic Mapping Program
Page Contact Information: Personnel
Page Last Modified: Thu 04 Apr 2024 03:28:03 PM MDT