Named Big Elk Creek Member of James Run Formation. Dark-green, gray quartz-plagioclase-hornblende amphibolite and felsite. Interlayered, layers 3-12 cm thick, of metavolcanic and metasedimentary origin. 305 m thick at type section. Gradationally overlies Gilpins Falls Member; probably partly equivalent to Happy Valley Branch and Principio Creek Members. Age is early Paleozoic.
Source: GNU records (USGS DDS-6; Reston GNULEX).
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