Document Type
Thesis
Abstract
Fires leave evidence behind in lakebeds through combustion products in sediments. These products range from small pieces of charcoal to single molecules. Though research has explored what charcoal and geochemicals in lake sediments can tell us about the history of fire, scientists haven’t yet discerned what specific properties of charcoal can tell us, or if patterns in charcoal and these molecules, called PAHs, connect to historical events. My thesis uses 300 years of sediment from Lake Matoaka to attempt to connect charcoal to the burning material that created it. Additionally, I explore how different types of molecules indicate different fire conditions, and whether these two environmental indicators relate to the well-documented history of Lake Matoaka and Williamsburg, Virginia. I discovered that the shape and proportion of charcoal in these sediments changed as land use in the region changed, and that PAH amounts increased as population in the area did. Before the Revolutionary War (around 1780), charcoal shapes showed more agricultural activity in the region, while during the Civil War and into the twentieth century changing charcoal properties related to increased industrial development and population growth. Observing changes in PAHs over time showed a connection between young forest burning and local burning- this may connect to wooden buildings catching fire in a time period where candles and fireplaces were primary sources of light and heat. My molecule timelines also reflected the increasing fossil fuel use in the twentieth century. Additionally, I was able to suggest two improvements for charcoal study in this region: first, that a new key be developed for charcoal shapes in this particular region, and second, that charcoal circularity is impacted by weathering. Overall, my research connected two fire products in Lake Matoaka sediment to Williamsburg’s history.
Date Awarded
Spring 2022
Department
Geology
Advisor 1
Richard Vachula
Advisor 2
Nicholas Balascio
Recommended Citation
DePue, Lee, "Paleofire Proxies in a Lake Matoaka Sediment Core: Macroscopic Charcoal and Polycyclic Aromatic Hydrocarbons" (2022). Geology Senior Theses. William & Mary. Paper 43.
https://scholarworks.wm.edu/geologyseniors/43
