Decoupling of the carbon cycle during Ocean Anoxic Event 2

摘要: The Cenomanian to Turonian boundary transition (ca. 95–93 Ma) represents one of the most profound global perturbations in carbon cycle past 140 m.y. This interval is characterized by widespread deposition organic-rich fine-grained sediment marked a globally recognized positive isotope excursion (CIE) reflecting removal 12 C-enriched organic matter marine sediments under anoxic greenhouse conditions. However, exact timing and trigger this inferred phenomenon, termed Oceanic Anoxic Event 2 (OAE-2), still debated, with recent studies showing diachroneity between CIE, conflicting interpretations on detailed redox analyses several these settings. Here we present first evidence for persistent oxygenation during OAE-2 based primarily distribution redox-sensitive trace metals biota preserved sedimentary rocks from Western Interior Seaway North America. Our data indicate anoxic-euxinic conditions mid- late Cenomanian, but improved bottom-water prior CIE. Trace metal enrichments support large volumes mafic volcanism possibly High Arctic igneous province (HALIP), which occur within middle CIE indicating that emplacement LIPs was not primary Cenomanian-Turonian apparent paradox an oxygenated phase suggests much more complex than previously thought. These findings have important implications changes over time scales 0.1–10