Earth and Planetary Sciences ETDs

Publication Date

Summer 5-13-2024

Abstract

Diatom assemblage reconstruction from the Valles Caldera sediment core (VC-3) was utilized to infer climatic and aquatic changes during a 50-thousand-year [ka] period in the Mid-Pleistocene (435-385 ka). This 50 ka interval spans most of Marine Isotope Stage 11 (MIS 11) – one of the most prominent interglacials of the past 500 ka – and is widely considered an analog for the Holocene and future climate regimes. Nearly all records from MIS 11 are either marine or ice-core based, making VC-3 unique among lacustrine sediment records as it captures insolation variations and climatic changes during the mid-Pleistocene. Analysis of the diatom community assemblages shows rapid shifts between benthic (bottom-dwelling) and planktonic (free-floating) taxa, indicating the lake that occupied the Valle Grande within the Caldera experienced variable lake-levels. Autecology of dominant species (>10% relative abundance) allowed for the interpretation of water conditions and lake bathymetry during the mid-Pleistocene: taxa that thrive in cold, oligotrophic occur in abundance before Glacial Termination V; species indicative of higher nutrient-flux characterize transgressional and regressional events in the Lake’s history; dominance of taxa that prefer shallow, eutrophic conditions occur coeval to mega-drought conditions; and low-density samples overlap with two ash-layer deposits (~397.2 and ~394.0 ka)

Level of Degree

Masters

Department Name

Department of Earth and Planetary Sciences

First Committee Member (Chair)

Peter Fawcett

Second Committee Member

Rebecca Bixby

Third Committee Member

Tyler Mackey

Keywords

Paleolimnology, diatom, paleoclimatology, climate change

Document Type

Thesis

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