TECTONIC AND METAMORPHIC EVOLUTION OF A TECTONIC MELANGE, RATTLESNAKE CREEK TERRANE, KLAMATH MOUNTAINS, NORTHERN CALIFORNIA

The Klamath Mountains region in Northern California contains an assembly of terranes representing the complicated geologic history of western North America from the Ordovician to the Cretaceous. The Rattlesnake Creek terrane (RCt) in particular is a tectonic mélange of metamorphosed sedimentary, mafic volcanic-plutonic, and ultramafic rocks with an extensive geologic history that includes tectonism, volcanism, and accretion. The geologic setting in which the RCt initially formed is speculated to be either endemic or exotic to North America. An endemic model will show evidence of continental material incorporated during the formation of the RCt, while an exotic model will display evidence of foreign mafic samples. Recent work shows that the RCt’s cover sequence has a North America provenance. Despite this connection, the history and tectonic setting of the RCt is not well-understood.

In order to test the endemic and exotic models for the RCt, this project will conduct field work, sandstone petrography, and detrital zircon geochronology. Field work in the RCt provides samples of metasedimentary blocks and orientations of structures explaining the RCt’s current place in the Klamaths. Sandstone petrography, specifically the Gazzi-Dickinson point counting method, is used to explore the sediment composition and provenance. Detrital zircon geochronology is used to determine age populations and compare with possible sources. The combination of these methods will constrain the provenance of our samples with implications for the history of the RCt. The ultimate goal of this study is to determine the setting in which the RCt formed to provide more accurate information about the geologic history of the Klamath Mountains region.