Early Paleogene marine paleoenvironments: New insights from the geochemistry of fossil shells

The geochemical composition of fossil biogenic carbonate provides a means to document and study variations in ocean temperature and chemistry throughout Earth's history. In this dissertation the geochemical systematics of minor element incorporation in modern mollusks are discussed, and the stable isotope and minor elemental composition of fossil mollusks and foraminifera are applied to reconstruct paleoenvironments during the Paleocene and Eocene.; A set of studies was undertaken to characterize coastal sea surface temperatures during the early Paleogene using stable isotope measurements. Chapter One presents a reconstruction of an Arctic coastal environment during the late Paleocene. Chapter Two is a detailed reconstruction of tropical coastal temperatures during the late Eocene in an oligotrophic coastal setting near Panama. Chapter Three describes a planktonic foraminiferal Mg/Ca record for an equatorial Pacific site, spanning the Paleocene and Eocene (58 to 38 Ma). Using published models of secular variations in seawater composition, this Mg/Ca record is used to assess the long-term evolution of tropical sea surface temperatures in an oligotrophic open ocean setting. Chapter Four discusses the environmental controls on Sr/Ca ratios in both modern and early Paleogene aragonitic turritellid shells. Specifically, the distribution coefficient is determined for several modern species, and applied to Paleocene and Eocene specimens to estimate how seawater Sr/Ca ratios, and coastal seasonality, have evolved during the early Paleogene.