GEOCHEMISTRY OF THE IREVIKEN BIOGEOCHEMICAL EVENTS USING PARTIAL DIGESTION OF CARBONATE MATERIAL

The Silurian has several distinguishable excursions in the C and O isotope curve. The Ireviken Extinction Event spans the Llandovery-Wenlock boundary and is characterized by a massive loss of trilobite and conodont species. A positive carbon isotope excursion also comprises the overall Ireviken Biogeochemical Event. The event is best recorded in Gotland, Sweden and lasted longer than 1 Myr from the beginning of the extinction until the end of the carbon isotope excursion.

The focus of this study is the major-space and trace-element geochemistry of the Ireviken biogeochemical events and separating the geochemical record in the carbonate fraction from the silicate fraction using partial digestion. The methodology will be validated using the Altajme Core collected from Gotland, Sweden. Specifically, the interval spanning the Llandovery-Wenlock boundary. Samples will be analyzed via an Inductively Coupled Plasma – Mass Spectrometer (ICP-MS) at the University of Iowa MATFab Lab. The carbonate fraction of the rock will be selectively dissolved by first using acetic acid on the samples. After separating the carbonate component of the rock, both the carbonate and residual components will be analyzed via the ICP-MS. Along with this, a total digestion process of the samples will also be done without separating out the carbonates. Thus, a comparison of the results from the carbonate fraction vs. whole rock digestion will determine if there are any differences in the chemical signature of the different lithologies in the rock. Using this methodology will help isolate geochemical signals from carbonates within mixed lithology strata. This process will help to determine which mineral phases are hosting individual elements and potentially will help to evaluate the roles of scavenging and post depositional enrichment during this event.