Jennifer Kasbohm – PhD Candidate from the Department of Geosciences, Princeton University
Title: Rapid eruption of the Columbia River flood basalt and correlation with the Miocene Climate Optimum
Abstract: Flood basalts, the largest volcanic events in Earth history, are thought to drive global environmental change because they can emit large volumes of CO2 and SO2 over short geologic timescales. Eruption of the Columbia River Basalt Group (CRBG) has been linked to elevated atmospheric CO2 and global warming during the Miocene Climate Optimum (MCO) ~16 million years ago. However, a causative relationship between volcanism and warming remains speculative as the timing and tempo of CRBG eruptions is not well known, due to large analytical uncertainties inherent in the previously used K-Ar and 40Ar/39Ar methods. We use CA-ID-TIMS U-Pb geochronology on zircon-bearing volcanic ash beds intercalated within the basalt stratigraphy to build a high-resolution (ca. 10 kyr) CRBG eruption record. Our dataset shows that more than 95% of the CRBG erupted between 16.7 and 15.9 Ma, twice as fast as previous estimates, potentially allowing for a more pronounced climatic perturbation. Our new eruptive timeline can be compared to marine proxy records of the MCO. Given the well-defined CRBG magnetostratigraphy, our data suggest a recalibration of the Geomagnetic Polarity Timescale (GPTS) during an interval when several reversal ages are disputed. When comparing our CRBG eruptive chronology with records with reliable magnetostratigraphy, we find that the onset of CRBG volcanism falls in the same magnetic chron as the onset of the MCO. Further work that refines age models for climate proxy records across the MCO and investigates rates of eruptions for the CRBG is required before a temporal correlation can be established. Our work shows the importance of accurate and precise temporal constraints to assess causal mechanisms of global warming events.
Where: RUCH 103
When: Monday, October 28th