Title

Prelliminary analysis of strain the Tuttle Lake Formation, Desolationi Wilderdess Area, El Dorado County, Calfornia

Poster Number

3

Lead Author Major

Geology

Format

Poster Presentation

Faculty Mentor Name

Kurtis Burmeister

Faculty Mentor Department

Earth and Environmental Sciences

Abstract/Artist Statement

The results of recent fieldwork and a preliminary analysis of grain-scale fabrics suggest that strain is unequally partitioned between the grain and outcrop scales in rocks from the Tuttle Lake Formation near Grass Lake. Here, the Tuttle Lake Formation contains weakly metamorphosed, cross-bedded volcaniclastic conglomerate and breccia and is cut by a series of igneous intrusions that include at least five sets of mafic to intermediate dikes and a granitic pluton. Outcrop-scale observations made during geologic mapping in the summer of 2014 suggest that the magnitude of strain in the Tuttle Lake Formation may increase with proximity to these intrusions. To examine outcrop-scale strain, we performed a normalized Fry analysis using the outlines of clasts traced with permanent markers onto clear plastic sheeting. Digital photographs of these traces were then imported into the EllipseFit computer program for analysis (Vollmer, 2015). Samples of the Tuttle Lake Formation were also collected to investigate if this relationship in strain magnitude was also present at the microscopic, grain scale. Three mutually perpendicular, large-format petrographic thin sections were prepared from each of these samples. Digital photomicrographs of these thin sections were then used to conduct a three dimensional normalized Fry strain analysis with the EllipseFit program. The results of these analyses underscore the importance of quantifying strain at both grain and outcrop scales. The results of this work are being used to formulate a new research strategy for summer 2015 that will include a better sampling strategy for grain-scale analysis and a more widespread outcrop-scale sampling effort.

Location

DeRosa University Center, Ballroom

Start Date

25-4-2015 2:00 PM

End Date

25-4-2015 4:00 PM

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Apr 25th, 2:00 PM Apr 25th, 4:00 PM

Prelliminary analysis of strain the Tuttle Lake Formation, Desolationi Wilderdess Area, El Dorado County, Calfornia

DeRosa University Center, Ballroom

The results of recent fieldwork and a preliminary analysis of grain-scale fabrics suggest that strain is unequally partitioned between the grain and outcrop scales in rocks from the Tuttle Lake Formation near Grass Lake. Here, the Tuttle Lake Formation contains weakly metamorphosed, cross-bedded volcaniclastic conglomerate and breccia and is cut by a series of igneous intrusions that include at least five sets of mafic to intermediate dikes and a granitic pluton. Outcrop-scale observations made during geologic mapping in the summer of 2014 suggest that the magnitude of strain in the Tuttle Lake Formation may increase with proximity to these intrusions. To examine outcrop-scale strain, we performed a normalized Fry analysis using the outlines of clasts traced with permanent markers onto clear plastic sheeting. Digital photographs of these traces were then imported into the EllipseFit computer program for analysis (Vollmer, 2015). Samples of the Tuttle Lake Formation were also collected to investigate if this relationship in strain magnitude was also present at the microscopic, grain scale. Three mutually perpendicular, large-format petrographic thin sections were prepared from each of these samples. Digital photomicrographs of these thin sections were then used to conduct a three dimensional normalized Fry strain analysis with the EllipseFit program. The results of these analyses underscore the importance of quantifying strain at both grain and outcrop scales. The results of this work are being used to formulate a new research strategy for summer 2015 that will include a better sampling strategy for grain-scale analysis and a more widespread outcrop-scale sampling effort.