Provenance and Petrofacies, Upper Devonian Sandstones, Philip Smith Mountains and Arctic Quadrangles Brooks Range, Alaska
Issue Date
1987Keywords
Geology -- Alaska -- Brooks RangeGeology, Stratigraphic -- Devonian
Sandstone -- Alaska -- Brooks Range
Facies (Geology) -- Alaska -- Brooks Range
Brooks Range (Alaska)
Advisor
Coney, Peter J.Committee Chair
Coney, Peter J.Metadata
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The University of Arizona.Rights
Copyright © is held by the author. Digital access to this material is made possible by the Antevs Library, Department of Geosciences, and the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author or the department.Collection Information
This item is part of the Geosciences Theses collection. It was digitized from a physical copy provided by the Antevs Library, Department of Geosciences, University of Arizona. For more information about items in this collection, please email the Antevs Library, antevs@geo.arizona.edu.Abstract
A petrographic study of upper Devonian sandstones (Endicott and Hammond Terranes), Philip Smith Mountains and Arctic quadrangles, Brooks Range, Alaska, shows that the sand-sized detritus was derived from two petrographic provenances. Detrital modes, calculated from point counts of thin sections, show that the provenance for the Devonian clastic wedge (Endicott Terrane) was a recycled orogenic belt with major components of quartz, chert, and lithic fragments. Three petrofacies are distinguished. Their distribution indicates compositional changes vertically and laterally which reflect changing compositions in the source area. A petrographically different provenance supplied the sandstones that overlie the Skajit Limestone (Hammond Terrane). Characterized by high feldspar and abundant volcanic rock fragments, this petrofacies indicates first-cycle deposition close to the source area. A magmatica arc provenance is suggested.Type
textThesis-Reproduction (electronic)
Degree Name
M.S.Degree Level
mastersDegree Program
Graduate CollegeGeosciences
Degree Grantor
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Geology, U‐Pb Geochronology, and Hf Isotope Geochemistry Across the Mesozoic Alaska Range Suture Zone (South‐Central Alaska): Implications for Cordilleran Collisional Processes and Tectonic Growth of North AmericaThe Mesozoic Alaska Range suture zone is defined by a transition from oceanic to continental terranes and is part of a 2000-km-long tectonic boundary throughout the northern Cordillera. Surface geologic mapping of the rock types across this suture zone provides critical information about the upper crustal configuration but provides little insight into the sedimentary, igneous, and metamorphic processes that occurred in deeper levels of the collisional zone. To better constrain the timing and mantle-crust sources of collision-related magmatism, we combine U-Pb ages and Hf isotope compositions of detrital zircons from the three main components of the suture zone. U-Pb/Hf data sets from inboard, continental margin samples have Precambrian-Paleozoic ages with epsilon Hf-(t) values ranging between +10 and -20. U-Pb/Hf data sets from the outboard, oceanic terrane samples have Pennsylvanian-Permian detrital zircon ages with epsilon Hf-(t) values between +16 and +10. The U-Pb/Hf data set of detrital zircons from Mesozoic strata that represent intervening sedimentary basin(s) that formed between the continental margin and oceanic terranes record Precambrian-Mesozoic detrital zircon ages with epsilon Hf-(t) values between +14 and -20. Results of the study document four Archean and Proterozoic global crustal magmatic events that are correlated to the tectonic growth of Laurentia. Also, three Phanerozoic magmatic events have been identified that represent more regional tectonic events. This study demonstrates that the combination of U-Pb geochronology and Hf isotope geochemistry applied to detrital zircons is a powerful tool to define sediment provenance in collisional zones and delineate episodes of global and regional magmatism along convergent plate boundaries.
