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Publication Date

2022-01-18

First Advisor

Gregory de Wet

Document Type

Honors Project

Degree Name

Bachelor of Arts

Department

Geosciences

Keywords

paleoclimatology, biogeochemistry, paleoclimate reconstruction, brGDGTs, paleotemperature proxy, glacial-interglacial cycles, Tasmanian climate

Abstract

Reconstruction of past temperature and other paleoenvironmental conditions has increasingly become important to improve our understanding of the climate system and prepare for future climate because past conditions, especially intervals warmer than today, are useful analogs for future climate under ongoing global warming. Tn this project, we reconstructed past temperature from samples collected from a lake sediment core from Darwin Crater, western Tasmania, Australia using the branched glycerol dialkyl glycerol tetraether (brGDGT) biomarker paleotemperature proxy. The Darwin Crater sediment record is a powerful archive for paleoclimatic reconstructions as it spans approximately the last 800,000 years, consisting of multiple glacial-interglacial cycles. This work focused on an upper section of the Darwin Crater sediment core that likely spans the transition from a glacial period (presumably Marine Tsotope Stage (MTS) 6) to an interglacial period (presumably MTS 5), including a cool stadial (5d) and multiple warm interstadial (MTS 5e, 5c) intervals. Through this project, we aimed 1) to reconstruct past temperature at Darwin Crater using the brGDGT biomarker proxy, 2) to explore the efficacy of the brGDGT as a paleotemperature proxy, and 3) to advance our understanding of regional paleoclimate and paleoenvironment in Tasmania, Australia over long timescales. Our results seem to capture the expected temperature variability associated with the shift from a glacial to an interglacial period. They broadly agree with pollen data from the same sediment core, implying the brGDGT biomarker is an effective paleotemperature proxy at this study site. Our results also suggest that the regional Tasmanian climate was warmer and possibly wetter than today during this time. To date, this is the highest resolution construction of temperature from this interval for the study region. However, our ii analysis also concludes that there may have been local changes in the depositional environment that could have influenced our temperature reconstruction, illustrating some potential limitations of brGDGT proxy and the need for further investigation.

Rights

©2022 Ibuki Sugiura. Access limited to the Smith College community and other researchers while on campus. Smith College community members also may access from off-campus using a Smith College log-in. Other off-campus researchers may request a copy through Interlibrary Loan for personal use.

Language

English

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