Date of Award

5-2022

Document Type

Thesis campus only

Department

Geology

First Advisor

Kathleen Surpless

Abstract

The Galice Formation, a metasedimentary unit in the Western Klamath Terranes, was deposited in the Late Jurassic before and during the Nevadan Orogeny. Detrital zircon U-Pb age data and Lu-Hf isotope data were collected from eleven samples from the Galice Formation in order to better understand the timing of deposition and provenance of the Galice Formation. These results can also be used to constrain the tectonic setting of the Nevadan Orogeny. The maximum depositional ages (MDA), which approximate the true depositional age of the samples due to the proximity of the Galice Basin to arc sources, range from 156.7 +/- 2.0 to 148.7 +/- 2.1 Ma, suggesting an approximately 10 million year period of deposition for the turbidite sequence of the Galice Formation. These MDAs also place deposition both before and during deformation associated with the Nevadan Orogeny. Samples with younger MDAs tend to have a higher percentage of Mesozoic grains and also have similar age spectra to Jurassic eolianite strata in the Sierran retroarc, whereas samples with older MDAs tend to have a higher percentage of Precambrian grains and are more similar to the Sierra Nevada pre-batholithic framework age spectra. The Lu-Hf isotopic data shows a similarity between the Mesozoic grains of the Galice Formation and the Klamath Mountains, Sierra Nevada pre-batholithic framework , and possibly the Insular superterrane. No evidence is found for Galice Formation provenance in northern sources such as the Blue Mountains. Altogether, the detrital zircon data suggests that the Galice Formation at first had more distal sources such as the Sierra Nevadan arc and retroarc region before topographic development of the nearby arcs to the east and west shifted the provenance to these more proximal sources while also allowing for influx from different inland sedimentary units such as the Jurassic eolianites. Combined with the fact that the data supplies no evidence vi for Galice Formation provenance in northern sources such as the Blue Mountains, the Galice likely sourced sediments from the east and southeast as well as proximal arcs.

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