Name applied to a highly deformed succession of amphibolite grade rocks in the north-central Sierra Madre, Carbon Co, WY, Northern Rocky Mountain region, that are unconformably (or a faulted unconformity) over older Archean gneissic terrane and unconformably (or a faulted unconformity) under younger Deep Gulch Conglomerate Member (named) of the Jack Creek Quartzite (revised) of the Phantom Lake Metamorphic Suite. Named for Vulcan Mountain in the north-central Sierra Madre, Carbon Co, WY. Type area designated as exposures that extend northwest from South Spring Creek Lake to Strawberry Creek parallel to East Fork of Savery Creek in Ts14 and 15N, R86W. This outcrop area is approximately 14 km long and 1 km wide. Contains fine-grained amphibolite, metabasalt, hornblende gneiss, quartzite, chlorite schist, marble, and pillow basalts. Petrographic data. Stratigraphic chart. Geologic map. Mineralogy reflects epidote-amphibolite to amphibolite facies of metamorphism. Estimated to be 360 m thick. Considered Late Archean. Intruded by Spring Lake Granodiorite (named) which has a 2,700 Ma age. Correlated with Overland Creek Gneiss of Medicine Bow Mountains.

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