EVALUATING THE RELIABILITY OF USING NITROGEN ISOTOPES AS REDOX PROXIES IN PETROLEUM SYSTEMS: A REVIEW

Recently, bulk sedimentary nitrogen isotope (δ¹⁵N) profiles have been investigated in petroleum systems as potential proxies for paleoredox conditions during deposition. While the use of nitrogen isotopes as paleoredox proxies is generally supported in sediments that have undergone minimal organic matter alteration, the post-depositional sedimentary processes involved with hydrocarbon production may have altered the original δ¹⁵N signal in petroleum systems. In this presentation, we review recent evidence for alteration of the depositional δ¹⁵N signal due to diagenesis, catagenesis, and fluid migration, and how these alterations impact interpretation of nitrogen isotope profiles. We will also discuss the applications and limitations of using δ¹⁵N values as a proxy for evaluating paleoredox and paleoenvironmental conditions in different types of petroleum systems. Finally, we will illustrate how insights from bulk sedimentary δ¹⁵N can be combined with other sedimentary proxies to arrive at more robust paleoenvironmental interpretations for mid-continent petroleum producing units.