Granitic rocks of the Robertson River Pluton intrude Precambrian Y gneisses in the core of the Catoctin-Blue Ridge Anticlinorium in northern Virginia. Cobbles and boulders of lithologically similar granite are present in the overlying Mechum River and Fauquier (Lynchburg) formations. Dikes of metabasalt, texturally and lithologically similar to the flows of the Catoctin Formation cut the Robertson River Pluton. The Catoctin metavolcanic rocks themselves were extruded following deposition of the Fauquier and correlative clastic sedimentary rocks.

Zircons from four samples of the Robertson River Pluton yield a discordant U-Pb age of 730 m.y., indicating that the Catoctin Formation is considerably younger than the 820 m.y. previously assigned.