On The Use of Stable Nitrogen Isotopes in Present and Past Anoxic Environments

Abstract

Knowledge about the biogeochemistry of nitrogen cycling in modern aquatic ecosystems and the associated fractionations of nitrogen isotopes ($δ$15N) has increased significantly during the past two decades. These insights also improved our ability to interpret $δ$15N records recovered from ancient sediments. Specific environmental setups such as coastal upwelling areas, open pelagic realms, or stagnant basins are characterized by distinct biogenic processes and the formation of a typifying sedimentary record. We find growing evidence to recover these distinct biogenic processes in detail from $δ$15N patterns observed in earth history. Sediments with elevated nitrogen contents (>0.2{\%}) and low diagenetic offprint are most suitable for such investigations. The analysis of $δ$15N in extracted biomarkers such as chlorines and porphyrines, or from nitrogen bearing hard parts of certain fossils offer valuable tools to assess the sample quality and a possible imprint derived from diagenesis.