231 TH
The general audience will be invited to leave after the presentation and Q & A session.
Title: Stable Isotope and K-Bentonite Geochemistry of the Ireviken Biogeochemical Event from Gotland, Sweden
Abstract: The Silurian Period (approximately 444 to 419 million years ago) contains at least seven major biogeochemical events in Earth history that consist of an extinction event and perturbation to the global carbon cycle. The most extensively studied of these events known as the Ireviken Biogeochemical event (IBE) records major perturbations to nutrient cycling during and prior to what has now been identified as an oceanic anoxic event (OAE). Precise correlation of this event from multiple drill cores utilizing apatite rare earth element (REE) profiles from dissolution and Laser Ablation-Inductively Coupled Plasma-Mass Spectroscopy (LA-ICP-MS) analyses allows us to precisely correlate the highest resolution records of this event recorded in the Altajme and Lusklint-1 cores from the island of Gotland, Sweden.
The Altajme and newly drilled Lusklint-1 cores represent two distinct marine environments and precise correlation allows us to compare the cascade of events that comprise the IBE in deep and shallow waters for the first time. The comparison of two high-resolution records of carbon, nitrogen, and oxygen isotopes presented here allows us to observe the encroachment of anoxia, increased organic carbon burial, and changes in nutrient cycling into shallower waters during this event. Within this event one prominent question remains, what is the initial cause leading to this major biogeochemical event? Current ideas focus on an influx of biologically significant nutrients into the water column that generated an increase in primary productivity and resulted in deoxygenation, and ultimately the OAE. Here we utilize lithium isotopes, and the Chemical Index of Alteration (CIA) to determine if nutrients sourced from enhanced continental weathering could have contributed to the initiation of this major biogeochemical event.