Author ORCID Identifier

https://orcid.org/0000-0001-5735-0034

Year of Publication

2020

Degree Name

Doctor of Philosophy (PhD)

Document Type

Doctoral Dissertation

College

Arts and Sciences

Department

Earth and Environmental Sciences (Geology)

First Advisor

Dr. Michael McGlue

Second Advisor

Dr. Andrea Erhardt

Abstract

Three distinct manuscripts comprise this dissertation. The first analyzes the modern sedimentary basin of June Lake, a small glacial lake in the eastern Sierra Nevada of California (USA) using a number of data sets, including bathymetry, surface sediment composition, and seismic stratigraphy. The seismic survey revealed sublacustrine morphological features that suggest the basin originated due to ice scour, as well as four acoustically distinct stratigraphic units that reflect the history of sedimentation following glacial scouring. Corroborating the seismic record, sediment cores from the youngest unit are composed of hemipelagically deposited, organic-rich, laminated diatomaceous oozes alternating with coarse tephra beds. The oozes occur in profundal areas of the modern lake floor, and are characterized by high organic carbon and nitrogen values, and a low carbon to nitrogen ratio, consistent with an algal-dominated productivity regime, and preservation of organic matter at depth. Additional modern facies include poorly sorted coarse detrital landslide deposits below steep basin walls, and volcaniclastic sandy gravel in windward littoral areas. Thus, surface sediment grain size distribution and geochemistry are controlled by bathymetry and basin morphology. These data provide a baseline for the subsequent paleolimnological study of June Lake sediment cores.

The second paper presents geochemical and lithological data from a sediment core in an effort to contextualize recent and past changes in biological production and hydroclimate over the last ~ 4600 years at June Lake. The earliest part of the record coincides with the Neopluvial, and is characterized by high productivity and wetter conditions. This interval is followed by a series of distinct and prolonged droughts recorded as beds of carbonate from ~ 3600-1700 cal yr BP. This interval, known regionally as the Late Holocene Dry Period, has been associated with a negative Pacific Decadal Oscillation and La Niña conditions. The interval from ~ 1700 to ~ 130 cal yr BP is characterized by less frequent droughts and generally high production, and includes both the Medieval Climate Anomaly and the Little Ice Age. Marked declines in nearly all production indicators at ~ 130 years ago suggest an abrupt shift to drier conditions. This shift likely stems in part from anthropogenic warming, suggesting that the modern lake is anomalous with respect to the Late Holocene record of change in the basin.

The third paper details the results of a collaborative effort from UK’s Department of Earth and Environmental Sciences and a STEAM-focused high school to introduce geoscience content at the ninth-grade level. It was hypothesized that after having been exposed to project-based geoscience content, these students would be more interested in pursuing a geology major or career. However, the attitudinal survey indicated that the students viewed geology as a low-prestige, relatively low-paying career option, even after a semester of geoscience content. This is in spite of attitudes that might suggest an interest in geoscience, including a preference for environmentally friendly careers, the perceptions that family and friends would support a geology career, and interest in outdoor activities. It was also noted that interests developed before high school were key influences on college major, which suggests that particular attention should be paid to how geoscience content is implemented in primary and middle school curricula.

Digital Object Identifier (DOI)

https://doi.org/10.13023/etd.2020.259

Funding Information

National Science Foundation (NSF) through GEOPATHS-IMPACT Award #1600399 (2016-2019)

U.S. Department of State, Mission to India, Award SIN65017GR0008 (2017-2018)

Overcash Fund for Field Research (2016)

Alumni donors to the UL Field Geology Fund (2016)

Lawrence Livermore National Laboratories Grant 17-ERD-052 (LLNL-JRNL-764279) (2016-2019)

Available for download on Monday, May 23, 2022

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