Lei, Yanyan
(2022)
Investigating Biomarkers in Lacustrine Sediments in Mexico and Central America and Developing Calibrations for Regional Paleoclimate Reconstruction.
Doctoral Dissertation, University of Pittsburgh.
(Unpublished)
Abstract
The study of paleoclimates allows us to evaluate the mechanisms of past climate change and helps unravel human influences on 20th century warming. However, our understanding of the North American tropical paleoclimate is hampered by lack of continental sedimentary archives. A 350m lacustrine sequence was recovered from Lake Chalco, Mexico, which has the potential to shed light on paleoclimate changes in this region over the past ~300,000 years.
Nestled within lake sediments, fossil molecules (called biomarkers) record how climates change around them at the time the organisms producing the biomarkers lived. Thus, the distribution and abundance of biomarkers provides evidence of past climate changes and have become an important tool in paleoclimate research. In recent decades, significant progress has been made in understanding the environmental controls on biomarker distributions, allowing for quantitative temperature and precipitation reconstructions in many systems.
The North American Neotropics are under the influence of a number of climatic drivers, including the Intertropical Convergence Zone, North American Monsoon, and El Nino-Southern Oscillation. Moreover, the complex topography makes it more difficult for climate studies to separate real climate change from more localized shifts in microclimate. For paleoclimate reconstruction in such regions under convoluted climatic and environmental controls, it is important to conduct multi-proxy studies and develop robust calibrations of measurable parameters (such as biomarker distributions) to desired paleoclimate parameters (such as temperature).
In my research, I evaluate a range of commonly applied biomarker proxies in lacustrine sediments of Mexico and Central America, discuss the latest development of biomarker related calibrations as applied to this region, and explore the potential of a suite of novel biomarkers identified in lake sediment samples. This work provides a framework for biomarker analyses in lacustrine sediments in Mexico and Central America, demonstrating that biomarkers, including leaf wax hydrogen isotope composition and bacterial membrane lipids, are capable of recording precipitation and temperature.
Furthermore, I developed new temperature calibrations from lacustrine surface sediments for application to paleoclimate reconstructions using Lake Chalco sediment cores. These new calibrations will help reduce bias in temperature reconstruction, thereby providing a robust tool for future research.
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Details
| Item Type: |
University of Pittsburgh ETD
|
| Status: |
Unpublished |
| Creators/Authors: |
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| ETD Committee: |
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| Date: |
30 April 2022 |
| Date Type: |
Publication |
| Defense Date: |
31 March 2022 |
| Approval Date: |
19 November 2024 |
| Submission Date: |
7 April 2022 |
| Access Restriction: |
No restriction; Release the ETD for access worldwide immediately. |
| Number of Pages: |
167 |
| Institution: |
University of Pittsburgh |
| Schools and Programs: |
Dietrich School of Arts and Sciences > Geology and Environmental Science |
| Degree: |
PhD - Doctor of Philosophy |
| Thesis Type: |
Doctoral Dissertation |
| Refereed: |
Yes |
| Uncontrolled Keywords: |
Biomarker
Paleoclimate
Lacustrine
Chalco
Mexico and Central America |
| Date Deposited: |
19 Nov 2024 16:37 |
| Last Modified: |
20 Nov 2024 16:59 |
| URI: |
http://d-scholarship.pitt.edu/id/eprint/43194 |
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