Nutrient cycling in the oligotrophic ocean over the past 65 million years ...

• Main Author: Auderset, Alexandra
• Format: Text
• Language: English
• Published: ETH Zurich 2020
• Subjects: PALEOCEANOGRAPHY; BIOGEOCHEMISTRY; Nitrogen cycle; Nitrogen isotopes; Foraminifera; Temperature reconstructions; Biomarker; Alkenones; GDGTs; glacial/interglacial cycles; Miocene; Eocene; Cenozoic; infoeu-repo/classification/ddc/550; Earth sciences; Planktonic foraminifera
• Online Access: https://dx.doi.org/10.3929/ethz-b-000449878; http://hdl.handle.net/20.500.11850/449878

Nitrogen (N) holds a central position in ocean biogeochemistry due to its role as a limiting nutrient for biological productivity in the ocean and its resultant influence on the marine carbon cycle. Nitrogen isotopes represent a powerful tool to investigate changes in the marine N-cycle across different timescales. However, their use in geochemical studies has been traditionally limited by the potential diagenetic artifact related to changes in organic matter preservation through geologic time. Over the past ten years, the analysis of the isotopic com- position of organic matter protected within the mineral structure of planktonic foraminifera shells (foraminifera bound, FB) has emerged as a way to circumvent diagenetic overprints of classical techniques. The objective of this thesis is to use this novel technique to study the evolution of the N-cycle over previously unexplored periods of the Cenozoic, with a particular focus on the late Pleistocene glacial cycles (Chapter 3), the Mid Miocene (Chapter 4), ...