The Temporal Dynamics of Terrestrial Organic Matter Transfer to the Oceans: Initial Assessment and Application

Nicholas Drenzek, Ph.D., 2007
Konrad Hughen, Timothy Eglinton, Advisors

This thesis employs compound-specific stable carbon and radiocarbon isotopic analysis of organic biomarkers to (a) resolve petrogenic from pre-aged vascular plant organic carbon (OC) in continental margin sediments, (b) investigate the underlying mechanisms controlling the anomalously old ages that are often observed for the terrestrial component of sedimentary OC, and (c) address the associated consequences for biomarker-based climate reconstructions. Coupled molecular isotope mass balances demonstrate that the amount of petrogenic OC in margin sediments has been previously overestimated due to the presence of significantly ‘pre-aged’ terrestrial OC, but is nonetheless still significant. Additionally, the vast majority of terrestrial OC at two study sites was determined to experience multi-millennial residence times on land prior to entering the sea. With this in mind, the striking modulation in the signal amplitude of a biomarker-based tropical paleoaridity record was instead used to evaluate the role of low versus high latitude forcing in abrupt paleoclimate oscillations during the last full glacial cycle. Seasonal variations in the position of the Intertropical Convergence Zone were interpreted to be a response to both high latitude adjustments in meridional overturning circulation and local insolation.