Description
Assessing the provenance and tectonic setting of sandstone dominated sequences is inherently difficult, because diagenesis and metamorphism commonly alter the framework compositions of meta-sandstones. However, recent work suggests that chemical data combined with petrological data can overcome these difficulties. Hence, I point counted and analyzed 23 metasandstones for major, trace, and rare earth elements from the Poison Canyon and Red Hill units of the Shoo Fly Complex in order to assess the effects of greenschist facies metamorphism on framework composition. Framework data derived from the Gazzi-Dickinson point count method indicate that the source of detritus was from a craton-interior to transitional continental-block provenance. However, samples contain high amounts of matrix/psuedomatrix, which may limit this technique. Consequently, QtF*L* and QmF*Lt* modes of each sample were determined following the methods of R. Cox and D.R. Lowe which corrects for labile fragment degradation. On QtF*L* and QmF*Lt* ternary diagrams data plot in the recycled orogenic field, a relationship consistent with the abundant argillaceous lithic fragments present in the samples, and the inferred subduction complex setting of the Shoo Fly Complex. The chemistry of the Poison Canyon and Red Hill units was evaluated to further constrain their source and tectonic setting. Chemical data plotted on the K2O/Na2O versus SiO2 discrimination diagram fall within the active to passive margin continental settings. In addition, the Poison Canyon and Red Hill units are characterized by low Fe2O3*+MgO, low TiO2, low Al2O3/SiO2, high K2O/Na2O, and high AlO3/(CaO+Na2O) which also suggest a passive to active continental margin. Furthermore, trace-element chemistry supports the idea that the Shoo Fly Complex was part of an arc-trench system that developed relatively near a continental source. Finally, REE data in combination with results from previously published detrital zircon work indicate the source of debris in the Shoo Fly Complex was dominated by post-Archean rocks, but also includes an unknown amount of Archean materials. Petrological and chemical data presented in this thesis point to a mixed provenance that included continental, island arc, and recycled orogen components. Regional relationships suggest that the source of continental detritus may have been located within Archean and post-Archean rocks of the Peace River arch of Canada and within the basement of a fringing Ordovician-Silurian island arc system. Island arc debris may have been derived from this adjacent island arc and/or within the Salmon River arch of eastcentral Idaho. The recycled orogen component may be due to sedimentary recycling of arc derived and/or continental derived materials that were accreted during earlier phases of subduction. Though the exact locations of the sources of detritus remain uncertain, the results of my study provide a clearer image of what those sources may have looked like. Thus, data described herein allow a comprehensive characterization of the source of the most extensive pre-Upper Devonian eugeoclinal sequence exposed in California.
