Title

Detrital zircon sample preparation of the Jurassic Tuttle Lake Formation, El Dorado County, California

Poster Number

20B

Lead Author Major

Geological and Environmental Science, Conc. Geology

Lead Author Status

Senior

Format

Poster Presentation

Faculty Mentor Name

Kurtis Burmeister

Faculty Mentor Email

kburmeister@pacific.edu

Faculty Mentor Department

Geological and Environmental Sciences

Abstract/Artist Statement

Preparation of a fine-grained sandstone collected from the Tuttle Lake Formation for detrital zircon analysis provided new insight into the mineralogy of Jurassic volcanic arc related strata in the southernmost Mt Tallac metamorphic roof pendant. The Tuttle Lake Formation is a weakly metamorphosed sequence of volcaniclastic sedimentary rocks deposited as debris flows in a shallow marine basin. Detrital zircon analysis of the Tuttle Lake Formation was undertaken in hopes of addressing compelling questions surrounding sources of sediment within the volcanic arc. Ages of zircon crystals determined through radiometric age analysis can be used to identify discrete populations that can be used to resolve the provenance of the sediment in a given area. We hypothesized that the zircons from the Tuttle Lake Formation either originated from within the Sierra Nevada volcanic arc or from the continental margin of North America. To test this hypothesis, we prepared our sample for detrital zircon analysis. Sample preparation involved separating zircon crystals from other minerals in the rock. This was accomplished through the combination of magnetic and heavy liquid separation techniques. Two rounds of magnetic separation were conducted using a Frantz Magnetic Separator, first set at a 20 degree tilt and 0.35 amps, and then at an 8 degree tilt and 0.60 amps. The resulting diamagnetic minerals were submerged in a tungsten-based heavy liquid, allowing for the separation of dense grains from lighter grains. Our results were unexpected – we were unable to recover a statistically valid population of zircon crystals. The absence of zircon crystals within our sample suggests that the interval sampled within the Tuttle Lake Formation is not an ideal candidate for this method of geochronological analysis. We have already identified a potentially better location for sample collection and hope to conduct a follow-up analysis to address questions surrounding this unit’s history.

Location

DeRosa University Center Ballroom

Start Date

27-4-2018 12:30 PM

End Date

27-4-2018 2:30 PM

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Apr 27th, 12:30 PM Apr 27th, 2:30 PM

Detrital zircon sample preparation of the Jurassic Tuttle Lake Formation, El Dorado County, California

DeRosa University Center Ballroom

Preparation of a fine-grained sandstone collected from the Tuttle Lake Formation for detrital zircon analysis provided new insight into the mineralogy of Jurassic volcanic arc related strata in the southernmost Mt Tallac metamorphic roof pendant. The Tuttle Lake Formation is a weakly metamorphosed sequence of volcaniclastic sedimentary rocks deposited as debris flows in a shallow marine basin. Detrital zircon analysis of the Tuttle Lake Formation was undertaken in hopes of addressing compelling questions surrounding sources of sediment within the volcanic arc. Ages of zircon crystals determined through radiometric age analysis can be used to identify discrete populations that can be used to resolve the provenance of the sediment in a given area. We hypothesized that the zircons from the Tuttle Lake Formation either originated from within the Sierra Nevada volcanic arc or from the continental margin of North America. To test this hypothesis, we prepared our sample for detrital zircon analysis. Sample preparation involved separating zircon crystals from other minerals in the rock. This was accomplished through the combination of magnetic and heavy liquid separation techniques. Two rounds of magnetic separation were conducted using a Frantz Magnetic Separator, first set at a 20 degree tilt and 0.35 amps, and then at an 8 degree tilt and 0.60 amps. The resulting diamagnetic minerals were submerged in a tungsten-based heavy liquid, allowing for the separation of dense grains from lighter grains. Our results were unexpected – we were unable to recover a statistically valid population of zircon crystals. The absence of zircon crystals within our sample suggests that the interval sampled within the Tuttle Lake Formation is not an ideal candidate for this method of geochronological analysis. We have already identified a potentially better location for sample collection and hope to conduct a follow-up analysis to address questions surrounding this unit’s history.