Date of Graduation

Spring 5-2015

Level of Access

Open Access

Degree Name

Bachelor of Arts

Department or Program

Geology

First Advisor

Michael Retelle

Abstract

Over the past century, the global climate system has experienced unprecedented warming due to the rapid increase of greenhouse gas concentrations. Thus, understanding the fate of CO2 once it is released is critical to evaluating the impacts of future climate change. Lake sediments have the potential to store large quantities of CO2 in the form of organic carbon, yet the factors which control organic carbon burial efficiency in lakes are not fully understood. Consequently, this project examines the sedimentary record from one lake spanning the boreal forest-tundra ecotone in the eastern Mealy Mountains of southeastern Labrador, Canada in order to identify lake and watershed controls on organic carbon accumulation and evaluate the sensitivity of organic matter accumulation to changing climatic conditions. The pronounced environmental gradient and significant post-glacial environmental changes in this region provide an ideal setting for testing controls on organic matter accumulation. This study presents results of a multi-proxy reconstruction of one sediment record recovered from a lake located in the Mealy Mountains (53°N, 58°W). Proxies used in this study included % organics (%LOI, %C, and %N), XRF elemental analysis, magnetic susceptibility, and fossil pigment paleoproductivity reconstruction. In order to evaluate changes in mass accumulation rate of organic carbon, two age models were generated based on seven radiocarbon dates. Contained within the sediment core collected from Moose Lake (ML-14-2) are three distinct lithostratigraphic units: unit A, B, and C. The top unit is described as a homogenous, organic rich gyttja that transitions into an inorganic, clastic unit containing both silt and clay. This visual classification of the core stratigraphy is further reflected by the several geochemical analysis used in this study and suggests that Moose Lake experienced a major shift in sediment accumulation and paleoproductivty ca. 6000 cal ye BP. Fossil pigment concentrations, which reflect rates of productivity, where highest in the inorganic unit. This suggests that fossil pigments may not be a good predictor of organic material accumulation. MAR of organic materials suggest that although accumulation rates of carbon are low, they may be sensitive to change in climate.

Open Access

Available to all.

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