Usage:
James Run Formation of Glenarm Group (DE*,MD*)
James Run Formation (MD)
Subunits:
Principio Furnace (MD*), laterally equivalent Little Northeast Creek (MD*) and Frenchtown Members (MD*), Gilpins Falls Member (DE*,MD*), laterally equivalent Big Elk Creek (MD*,DE*) and Principio Creek Members (MD*), Happy Valley Branch Member (MD*), and an unnamed felsite member at the top of the formation; Carroll Gneiss Member (MD), Druid Hill Amphibolite Member (MD), and Relay Gneiss Member (MD)
Geologic age:
Cambrian*
Type section, locality, area and/or origin of name:
Type locality: Gatch quarry, on James Run Road about 2.3 mi south of Churchville, [Bel Air 7.5-min quadrangle], Harford Co., northeastern MD (Southwick and Owens, 1969).
Named from exposures along James Run, southeastern Harford Co., northeastern MD (Southwick and Fisher, 1967).
AAPG geologic province:
Piedmont-Blue Ridge province*
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 ([ ]).