The lacustrine volcaniclastic deposits of the Ohanapecosh Formation, Washington


Pre-meeting field trip, August 10-13; max/min participation, 24/10

This 4-day field trip (10-13 August 2017) will cover the classic Tertiary Ohanapecosh Formation only a few hours drive from Portland at the foot of Mt Rainier and in the Cascades foothills. The Ohanapecosh Formation comprises a wide variety of volcaniclastic facies deposited in subaqueous settings but sourced mainly from subaerial explosive eruptions. We will examine fine to coarse units deposited from density currents associated with large-scale and small pyroclastic flows entering water, post-eruptive resedimentation, and fallout onto water. The succession is also highly instructive on the textural modification that accompanies diagenesis of volcaniclastic aggregates. One and a half days will be on road cut exposures within or close to the Mt Rainier National Park, whereas one day will consist of a hike (7 km return at ~2000 m elevation) to reach superb exposures with magnificent views of several Quaternary volcanoes. Return to Portland will include stops in the brewing area of the Yakima Valley, and scenic drive along the Columbia River Gorge and its famous basalts. This field trip is open to anybody interested in volcaniclastic sedimentation; we seek attendance from students to highly experienced researchers.

We will leave from Portland (exact location to be announced) and expect to be back in time for the conference ice-breaker on Sunday afternoon. A relatively good level of fitness (hike and scree slopes) is necessary for the hike day.

Estimated cost:
$730 in shared accommodation (recommended). This price includes the pre-field trip night (9th August) lodging in Portland, meals, and transport for the entire fieldtrip with the exception of 3 lunches.

Martin Jutzeler, University of Tasmania
Jocelyn McPhie, University of Tasmania