The vast majority of theses in this collection are open access and freely available. There are a small number of theses that have access restricted to the WWU campus. For off-campus access to a thesis labeled "Campus Only Access," please log in here with your WWU universal ID, or talk to your librarian about requesting the restricted thesis through interlibrary loan.
Date of Award
Department or Program Affiliation
Master of Science (MS)
Wildfires are expected to increase in frequency and severity as climate changes in the Pacific Northwest of North America. To better understand the effect of warming climate on wildfire regimes, I present the first reconstruction of past wildfire frequency and severity during the Paleocene-Eocene transition in northwest Washington state, U.S.A. The Chuckanut Formation is a late Paleocene to Eocene sedimentary unit with a robust paleobotanical record showing the existence of subtropical forests in northwest Washington during the Paleocene, transitioning to a relatively cooler Eocene, dominated by temperate mixed forests. Geochemical records of environmental change coinciding with Paleocene-Eocene climatic change in this region are understudied.
Polycyclic aromatic hydrocarbons (PAHs) are molecules produced during incomplete combustion of biomass that readily preserve in the sedimentary record and are used to reconstruct past wildfire frequency and severity. Analyses of PAH concentrations on Paleocene-age and Eocene-age members of the Chuckanut Formation indicate that wildfires were infrequent in the Paleocene, outside of two distinct stratigraphic intervals of increased fire activity, compared to more frequent wildfires in the Eocene. The aromatic structure of PAHs preserved in both members does not indicate a marked change in wildfire severity between the Paleocene and Eocene. I propose that a wetter hydroclimate during the Paleocene may explain the lower occurrence of wildfires compared to the Eocene, despite higher temperatures. Wildfire regime reconstructions combined with regional paleohydrology studies can provide insight into the environmental changes the Pacific Northwest may experience as a consequence of future climate change.
Chuckanut Formation, PAH, Wildfire Regime, Paleoclimate
Western Washington University
Subject – LCSH
Fire ecology--Washington (State)--Chuckanut Mountains; Wildfires--Washington (State)--Chuckanut Mountains; Paleoclimatology--Washington (State)--Chuckanut Mountains; Paleoclimatology--Paleocene; Paleoclimatology--Eocene; Biochemical markers; Polycyclic aromatic hydrocarbons; Chuckanut Mountains (Wash.)
Chuckanut Mountains (Wash.)
Copying of this document in whole or in part is allowable only for scholarly purposes. It is understood, however, that any copying or publication of this document for commercial purposes, or for financial gain, shall not be allowed without the author’s written permission.
Thompson, Alexandra, "Reconstructing wildfire regime during the warm Paleocene-Eocene climate using molecular biomarkers from the Chuckanut Formation in northwest Washington, U.S.A." (2023). WWU Graduate School Collection. 1261.