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Strong, Damara J (2017) BIOGEOCHEMICAL ANALYSIS OF LEAF WAX FATTY ACIDS FROM LAKE SURFACE SEDIMENTS IN MESOAMERICA. Master's Thesis, University of Pittsburgh. (Unpublished)

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Leaf wax hydrogen isotope (δD) values in paleoclimate records are a rapidly developing tool to
determine how precipitation has changed through time. Previous studies have demonstrated a
variation in fractionation of δD from precipitation and biomarker hydrogen isotope values due to
biosynthesis and other environmental factors including elevation, precipitation patterns, and
vegetation types, varying from region to region. This study focuses on identifying factors
contributing to variations in leaf wax fatty acid abundances and meteoric δD across a
Mesoamerican lake transect, as well as preliminary data identifying patterns in δD fractionation
from meteoric waters to fatty acids.
Lake core top samples were taken from over 150 sites throughout Mesoamerica. These
samples span environmental, elevational, and longitudinal gradients, and vary among lake types.
All samples exhibited an even-over-odd predominance of fatty acid chain lengths across
Mesoamerica, indicating little degradation of terrestrial input and successful recovery of leaf
waxes for δD analysis. Most samples exhibited a dominance in terrigenous fatty acid input into
the lake with short-chained fatty acids in relatively low abundance, assuring little contamination
to the lake sediment surface samples from petroleum byproducts and successful recovery of fatty
acids for δD analysis.
δD from lake waters (δDwater) from approximately 85 lake sites was analyzed for
comparison with leaf wax δD for quantifying fractionation during incorporation of δD into the leaf wax compounds. This study found an overall decline in δDwater values further from the coast
westward and an overall decline in δDwater values with increasing elevation, however the
correlations were insignificant with R2 values of 0.19 and 0.08, respectively. However, the pvalue
of longitude and elevation vs δDwater is 0.024, indicating a significant impact of these
independent factors on δDwater. δDwater analyses across elevational and longitudinal transects
demonstrate no clear uniform effects on δDwater values, indicating stronger local effects than
regional effects on δDwater.
Preliminary data demonstrate the potential for successful analysis of δD leaf waxes due to
the robust recovery of fatty acids from the lake sediments and initial results of effects on δDwater
for future interpretation in the δD leaf wax/water calibration and downcore lake sediment
paleoclimate studies.


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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
Strong, Damara Jdjk75@pitt.edudjk750000-0002-8554-1548
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee ChairWerne,
Committee MemberMcQuarrie,
Committee MemberElliott,
Date: 22 September 2017
Date Type: Publication
Defense Date: 5 July 2017
Approval Date: 22 September 2017
Submission Date: 31 July 2017
Access Restriction: No restriction; Release the ETD for access worldwide immediately.
Number of Pages: 132
Institution: University of Pittsburgh
Schools and Programs: Dietrich School of Arts and Sciences > Geology and Environmental Science
Degree: MS - Master of Science
Thesis Type: Master's Thesis
Refereed: Yes
Uncontrolled Keywords: hydrogen isotope composition, leaf waxes, biomarkers, precipitation, n-alkanoic acids
Date Deposited: 22 Sep 2017 20:55
Last Modified: 22 Sep 2017 20:55


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