Speaker

Kelsey Doiron, Ph.D., NSF Ocean Sciences Postdoctoral Fellow, Harvard University

New Perspectives in the Application of Alkenones as Paleoenvironmental Proxies in Marine and Lacustrine Setting

Abstract

Alkenones are a biomarker widely used in paleoceanography as proxies for reconstructing sea surface temperatures (UK37’) and pCO₂ levels, offering valuable insights into Cenozoic climate change through marine sediment archives. However, most studies utilizing alkenones as paleoclimate proxies focus solely on their applications within established limits, leaving a fundamental gap in our understanding including their evolutionary history. This talk explores two major aspects of my research that expand the use of alkenone biomarkers in underutilized settings including the Cretaceous period. First, I examine Campanian through Paleocene (~74–60 Ma) sediments from International Ocean Discovery Program (IODP) Site U1581, located off the coast of South Africa. Alkenones preserved in this southern hemisphere marine archive shed light on the origins of the alkenone sea surface temperature proxy and suggest the potential to extend its application into the Mesozoic era. Second, I present findings from Pleistocene lake sediments from Paleolake Olduvai in Tanzania, often referred to as the Cradle of Mankind, which reveal novel uses of alkenone carbon isotopic signatures beyond their traditional role in marine pCO₂ reconstructions. δ¹³C profiles of alkenones and other biomarkers from early Pleistocene sediments at Olduvai Gorge document environmental variability associated with alternating wet and dry cycles—an important context for understanding ecological pressures during a key interval of hominin evolution. Together, these case studies demonstrate that biomarkers—particularly alkenones—are not merely tools to be applied, but also frameworks to be expanded, offering new perspectives on both Earth system history and proxy development.