Sedimentary Radiogenic Isotopes as Tracers of Oceanographic and Atmospheric Change in the Eastern Equatorial Pacific Over the Last Glacial Period

Abstract

The purpose of this research is to investigate atmospheric and oceanographic change that affected the eastern equatorial Pacific Ocean (EEP), as archived in marine sediments from a single site in the Panama Basin, over the past 83,000 years. I focus my work exclusively on site MV1014-02-17JC (17JC) for its high sedimentation rates (18 cm kyr-1 on average) that allow me to construct very high-resolution geochemical records of climatic change. The primary concern is to evaluate how the EEP was impacted, if at all, by abrupt climate changes over the last glacial period and onset of the Holocene that include: Heinrich Stadial events, the last glacial maximum, the Bølling-Allerød, the Younger Dryas, and the early Holocene/African Humid Period. To this end, I explore how export production and phytoplankton community structure at 17JC varied in response to rapid fluctuations in nutrient delivery to the EEP with shifts in the Intertropical Convergence Zone (ITCZ) and changes in Southern Ocean climate over the deglaciation (25,000 years ago to present) using biogenic particle fluxes and sedimentary Pa/Th ratios. I also evaluate controls on sedimentary Pa/Th variability over the entire 83,000-year record. Finally, I utilize detrital Nd and Pb isotope ratios to consider dust provenance changes to 17JC that occurred with latitudinal migrations of the ITCZ and the southern westerly wind belt over the past 30,000 years. Overall, this work is significant in contributing a robust multi-proxy record of coeval oceanographic and atmospheric change that occurred in response to abrupt and glacial-interglacial climate change over the past 83,000 years in the EEP.