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Description
The Shoo Fly Complex, located in the northern Sierra Nevada, California, is an assemblage of lower Paleozoic oceanic rocks which have been interpreted to be the remnants of an ancient subduction complex. Petrological work indicates that the Shoo Fly Complex is in large part composed of terrigenous detritus shed from some nearby continental landmass. However, the identification of a specific unique source within this continental landmass has long perplexed geologists, as once sediment enters the marine realm, it tends to become well mixed and homogenized. Recent single-crystal detrital zircon work by George Gehrels of the University of Arizona indicates that late Precambrian to Early Paleozoic miogeoclinal sediment derived from the southern interior of North America is composed primarily of Proterozoic rock debris, whereas miogeoclinal sediment derived from the northern interior of North America was derived from Proterozoic and Archean rocks. To assess whether the provenance for detritus within the Shoo Fly Complex was located within either the northern or southern interiors of North America, argillite and sandstone samples collected from the Shoo Fly Complex were evaluated against argillite and sandstone samples collected from the southwestern part of the Cordilleran miogeocline. The results of work discussed in this thesis suggest that detritus in the Shoo Fly Complex is geochemically and statistically unlike detritus derived from Paleozoic rocks of the southern Cordilleran miogeocline. In contrast, when the rocks collected from the Shoo Fly Complex were averaged and evaluated against a combination of the miogeoclinal rocks and Archean sediments from the Yellowknife Supergroup of the Slave Province, Canada, similarities were observed. Moreover, chondrite-normalized REE distribution patterns of samples analyzed from the Shoo Fly Complex are consistent with derivation from a mixture of Archean and post-Archean detritus. The results of this thesis support the notion that the terrigenous detritus within the Shoo Fly Complex was derived from a mixture of Archean and post-Archean debris shed from the northern interior of western North America.
