Deschutes Formation and Tumalo Volcanic Center Field Trip

Co-Led by Jen Mcleod & Dr. Adam Kent

Saturday Sept. 17,

& Sunday Sept 18.

Please join Jen McLeod, doctoral candidate, and Dr. Adam Kent, both of Oregon State University, for a two day field trip focused on the Deschutes Formation and the Tumalo Volcanic Center.

The Deschutes Formation (~7.5-5 Ma) and Tumalo Volcanic Center (~0.6-0.13 Ma) represent two distinct periods of explosive silicic volcanism within central Oregon. These two localities are ideal for studying the processes that control silicic melt formation near the Cascade Arc, where high silica eruptive products are otherwise relatively rare. The Deschutes Formation is North America’s most recent ignimbrite flare-up, which includes ≥78 distinct explosive deposits located primarily within the modern Deschutes Basin. The Tumalo Volcanic Center, which lies between Three Sisters Volcanic Center and the city of Bend, OR, is a cluster of volcanic vents with several associated large ignimbrite deposits (e.g., the Tumalo Tuff, Shevlin Park Tuff, and Desert Springs Tuff). The tectonic constraints controlling melt formation at both the Tumalo Volcanic Center and the Deschutes Formation have long been an area of interest.

During this two day field trip we will compare the eruption histories of the Tumalo Voclanic Center and the Deschutes Formation and explore the regional tectonism that contributed to both of their development. We will first visit the Deschutes Formation to observe its remarkable ignimbrite flare-up stratigraphy and discuss its possible relationship to extensional processes. On the second day of the field trip, we will be visiting the Tumalo Volcanic Center to delve into its geochemical connection to the Cascades Arc and the nearby High Lava Plains volcanic track. During this field trip, we will be sharing newly acquired ⁴⁰Ar/³⁹Ar ages, geochemistry, and source information for Tumalo Volcanic Center eruptive units.

More information on itinerary to follow as well as details of meet up location and ride sharing opportunities.  This trip is designed as a two day integrated field trip.  Preference will be given to those who can commit to both days but COGS will attempt to accommodate those who can only attend one day.  Please go ahead and register but contact Derek Loeb ( DerekLoeb@gmail.com ) to specify which day you can attend.  You may also contact Derek with general questions.

This trip is limited to 15 participants.  All participants must be a COGS member or a guest of one and agree to the COGS liability waiver which requires all participants to self certify that they are fully vaccinated and boosted.  Please leave your pets at home.