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GSA Special Paper 517

The product of nearly 25 years of geologic investigations, this volume is an exposition of two small areas, both less than 25 km east of the Mississippian Roberts Mountains allochthon, but each displaying a different, unique geologic terrane, previously undocumented in Nevada and perhaps in North America. One area, the Bisoni-McKay, at the south end of the Fish Creek Range, displays an olistostrome, shed eastward during the late Late Devonian (early Famennian) from an eastward-migrating Antler orogenic forebulge. The other, the Warm Springs–Milk Spring, at the south end of the Hot Creek Range, displays a deeper marine terrane affected by the early Late Devonian (middle Frasnian) Alamo impact. New data show that the Antler orogeny began in latest Middle Devonian time, much earlier than previously thought. Detailed geologic maps support the conclusions, interpretations, and hypotheses presented in the text. The authors identified and dated Paleozoic rock units by studying nearly 100 acid-dissolved carbonate conodont samples and at least 50 collections of conodonts on siltstone bedding planes; they also redated Tertiary volcanic rocks and evaluated mineral and petroleum resources.