Typically exposed in White Mountains about 50 mi north of Fairbanks, just north of Fossil Creek in belt about 40 mi in length, Yukon-Tanana region, east-central AK. Consists of basic lavas, tuffs, breccias, and agglomerates of greenstone habit with small proportion of granular basic intrusives. Lower part is mainly bedded lavas and interbedded pyroclastic rocks. At very top of volcanic sequence is reddish calcareous rock, probably tuffaceous limestone containing fossils. Is about 2000 ft thick. At northeast end of White Mountains Fossil Creek volcanics occurs in compressed anticline between two synclines of Silurian Tolovana limestone (new). Age is Middle Ordovician based on fauna identified by Edwin Kirk (list and localities of fossils included in report).

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

Fossil Creek Volcanics unconformably overlies Wickersham grit unit of Late Proterozoic and Cambrian age. Underlies with erosional disconformity Tolovana Limestone of Silurian age. Detailed lithology, chemical analyses, and measured section of upper part of unit included in report. Conodonts from lower sedimentary part of unit and from gray limestone in uppermost part indicate Fossil Creek Volcanics is Early to Late Ordovician age.

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