April Meeting

Wednesday • April 18th 2018 • 6 – 9 PM

Old Market Pub • 6959 SW Multnomah Blvd, Portland, OR

6 PM — Social

6:45 PM — Dinner

(Salad & Pizza)

7:30 PM — Presentation

Reservations by 4 PM Monday, April 16th. Dinner $25*, Students FREE with RSVP ($5 if no RSVP). *There is a $2 surcharge for those who do not reserve by the deadline

Reservations can be made here: RSVP by 4pm Monday, April 16th

Insight into geologic mapping of mélanges from structural geologic research: Implications for engineering geologic analysis and illustration of the value of field geologic training

Guest Speaker: Dr. John Wakabayashi, Jahns Lecturer 2017-2018

With the continued decline in the amount and intensity of field training for geology students, researchers and young professionals are less well equipped to deal with the geologic complexity of mélanges than they were 10 to 20 years ago when they were already vexed. Detailed field work challenges the prevailing academic model of mélanges as mega shear zones (“subduction channels”) and shows that such mélanges formed as submarine landslide deposits. This leads to a significantly different model of processes along the subduction interface. It also has implications for practical mapping and characterization of mélanges for engineering purposes. A decade ago I had stated that the mode of mélange formation (sedimentary, diapiric, or tectonic) was not relevant to engineering characterization but I have shown this to be wrong, because different modes of formation make very different predictions for the distribution of materials and the nature of various contacts. The sad truth is mélanges are even more complex from a mapping standpoint than we had imagined a decade ago and this places a premium on geologic mapping skills and the training that builds such skills.



John Wakabayashi is a San Francisco Bay Area native who moved to Fresno in 2005 to begin his academic career as a geology professor at California State University, Fresno. He received his B.A. in Geology in 1980 from UC Berkeley, and his PhD in Geology in 1989 from UC Davis (advisor: Eldridge Moores). He is a Professional Geologist (California) and a Fellow of the Geological Society of America.

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