Decoupling δ~(13)C_(carb) and δ~(13)C_(org) at the onset of the Ireviken Carbon Isotope Excursion: Δ~(13)C and organic carbon burial (f_(org)) during a Silurian oceanic anoxic event

摘要

Paired records of delta C-13(carb) and delta C-13(org) across the Llandovery-Wenlock boundary demonstrate asynchronous behavior during the onset of the Ireviken Biogeochemical Event (IBE). The extremely high-resolution data produced from the Altajme Core, drilled from Gotland, Sweden, capture a negative excursion in delta C-13(org) during the initiation of the Ireviken Extinction Event (IEE) and prior to the onset of the Ireviken positive delta C-13(carb) Excursion (ICIE). The record of carbon isotopic changes through this interval illustrate that both Delta C-13 (the difference between delta C-13(carb) and delta C-13(org)) as well as the relative flux of organic carbon burial (f(org)) vary in unique ways and at different times during the progression of the IBE. Both process-oriented variables within the global carbon cycle (Delta C-13 and f(org)) track a series of events that help to demonstrate potential causative mechanisms of both the extinction and carbon cycle perturbation. The sequence of events demonstrated here largely mirror the cascade of events that took place during the Cretaceous Oceanic Anoxic Event 2 (OAE2) and a detailed comparison between the two events is provided here for the first time. The unique insight into the IBE presented in this work results primarily from the novel, nearly Neogene-scale resolution of the paired isotope data, which demonstrates the critical importance of high-resolution chemostratigraphic research to evaluating ancient perturbations to the Earth-life system. Additional data sets of equal or greater resolution through this interval will be critical to evaluate the global synchmneity of these short-lived events during the IBE, and similar high-resolution studies of other Paleozoic biogeochemical events may shed light on potentially similar causative mechanisms.