INVESTIGATIONS INTO THE YACHATS BASALT

The Yachats Basalt on the Southern Oregon Coast, reaching more than 6000 m from its Northernmost to its Southernmost point, was formed on an accreted terrane caused by the gradual compression, folding, and deposition of rocks due to the subduction of the Juan De Fuca Oceanic plate under the North American Continental plate. It is an excellent example of what happens when a volcanic hotspot transitions from type of tectonic plate to another. The largely surface basalt flows, dikes, breccias, and sedimentary deposits associated with the Yachats basalt were dated 40-32 Ma from the late Eocene, but recent research has reduced the estimate to 36-34 Ma. Recent research has also shown that the chemical composition of the Yachats basalt closely matches that of basalt expected from a volcanic hotspot rather than a Mid-ocean ridge. Although chemical analysis has demonstrated a notable difference between the Yachats basalt and the basalt of the younger Yellowstone eruptions, particularly a difference in lead concentrations, the chemical profile of the Yellowstone basalt is limited. However, we plan to investigate the chemical, physical, and visual similarities and differences between basalt samples from various points along the coastline bordering the Yachats basalt. To develop a complete and accurate chemical profile of the basalt, we will use primarily thin-section analysis and spectroscopy to identify which elements are present within the basalt. We aim to test if our findings can create a stronger correlation between the Yachats basalt and the basalt from the Yellowstone hotspot. If there is a connection between the two, it could also help determine the position of the hotspot relative to the subduction zone at the time of the eruptions.