Named the Relay quartz diorite for Relay, Baltimore Co., northeastern MD. Unit is pink quartz diorite composed of oligoclase, quartz, and muscovite. Intrudes Glenarm series. The Relay is of late Precambrian age.

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

Relay Quartz Diorite of Knopf and Jonas (1925) is here reduced in rank and assigned to the James Run Formation along with the Carroll Gneiss Member (new) and the Druid Hill Member (new). It was first suggested by Higgins (1972) that the unit is actually part of the James Run. The Relay as mapped by Knopf and Jonas and by Cohen (1937), crops out as two discrete masses: a narrow belt extending 11 km northward from the Patapsco River at Relay to Druid Hill Park, and a bulbous mass, 1 square km in size, just north of the park. However, this bulbous mass can be traced around the Jones Falls Schist and into the Carroll Gneiss Member, and is therefore not considered part of the Relay Gneiss Member of this report. The unit as described here is fine- to medium-grained biotite-quartz-plagioclase gneiss, locally containing muscovite and magnetite. At Relay the gneiss is quite mica poor, distinctly pinkish, and cut by many, randomly oriented joints. Thickness varies from 0 to 250 m. Age of the James Run and its members is shown as Cambrian(?).

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

The Relay is revised to the Relay Felsite and removed as a member of the James Run Formation in MD. Unit appears on map explanation of generalized geologic map of the MD Piedmont (figure 1) as part of the island arc rocks of the Bel Air-Rising Sun and Chopawamsic terranes.

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