Dissertation/Thesis Abstract

Paleomagnetic investigation of unlithified sediments from Clear Lake, Northern California and its chronostratigraphic and paleoenvironmental implications
by Levin, Emily, M.S., University of California, Davis, 2016, 72; 10182823
Abstract (Summary)

A sediment core from Clear Lake, CA that was drilled in 2012 is the centerpiece of a current interdisciplinary paleoclimate investigation in northern California. Two similar research projects were conducted in Clear Lake in 1973 and 1980, but inconsistent core recovery and a possible hiatus in sedimentation introduced uncertainty about the length of time represented by recovered sediments. Two cores recovered in 2012 were drilled in effort to create a continuous splice and attain a complete paleoenvironmental record for the Clear Lake area. Until now, the core has been radiocarbon dated to about 55 meters below lake floor (mblf) and one ash has been identified at 63 mblf, but the lower 90 meters of sediment remained undated.

Paleomagnetic research provides a chronostratigraphic framework for the collaborative project and reveals variations in sediment flux and environmental conditions over time. In Clear Lake sediments, magnetic minerals are ubiquitous and demonstrate reliable magnetic behavior for magnetostratigraphic interpretation, such as relative paleointensity (RPI) correlation. RPI correlation provides continuous chronostratigraphy for the core to 108 mblf, which corresponds to more than 200 ka.

Magnetic mineral concentration and grain domain size of Clear Lake sediments reflect zones of varying environmental conditions within the watershed that correlate with previous pollen research. These zones can be correlated to select Marine Isotope Stages (MIS), providing a direct link between paleoclimatic conditions in the marine and terrestrial environment in California. The boundary of MIS 1 and MIS 2, known to occur at 14 ka, is clearly shown as an increase in magnetic mineral concentrations responding to wetter conditions in MIS 2. These results are consistent with previous palynological interpretations from Clear Lake [Adam and Robinson, 1988]. Magnetic mineral concentrations reflect five zones of distinct environmental conditions and also suggests that sedimentation rate increases dramatically in the lower 30-40 meters of the core.

The environmental magnetic response of Clear Lake sediments, in conjunction with a magnetostratigraphic interpretation, provides a unique opportunity to investigate the timing of environmental change in the lake region. California’s current drought may be a new norm of extreme weather in response to higher average temperatures associated with climate change, and paleoenvironmental research like this provides insight on whole-system responses to rapid environmental change.

Indexing (document details)
Advisor: Verosub, Kenneth L.
Commitee: McClain, James, Osleger, David
School: University of California, Davis
Department: Geology
School Location: United States -- California
Source: MAI 56/01M(E), Masters Abstracts International
Subjects: Geology, Paleoclimate Science, Limnology
Keywords: California, Clear lake, Environmental magnetism, Limnogeology, Paleoclimate, Paleomagnetism
Publication Number: 10182823
ISBN: 978-1-369-31138-9
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