Trip leaders: Liz Schermer, Sean Mulcahy (WWU). This trip will focus on deformed oceanic rocks that were subducted and accreted to the margin of North America during Cretaceous time. We will examine the different styles of deformation in accretionary wedge and ophiolitic rocks, and the contractional and strike-slip deformation recorded in the Lopez structural complex along a major terrane boundary. The trip will involve a ferry ride to Lopez Island, several short walks (up to 1.5 mi RT) on trails, optional walking on rocky tideland outcrops, and roadside stops. Depart 8 a.m. Boxed lunch provided. Return ~ 6:30 p.m. Limited to 25 participants.
Part 1 (morning): An accessible field trip to the Twin Sisters dunite quarry. (Ok, really, it is mostly a lherzolite.) Trip lead: Basil Tikoff (UWisc). The quarry on the north side of the Twin Sisters massif is generally not available to the public. We will examine relatively fresh ultramafic rocks (the rocks are green) and discuss fabrics throughout the Twin Sisters ultramafic body. We will drive right up to the outcrop. Limited to 25 participants.
Part 2 (afternoon, on campus): An informal hands-on workshop for studying ultramafic rocks. Workshop lead: Julie Newman (TAMU). We will provide ultramafic rock hand samples and thin sections from around the world, including ultramafic ultramylonite zones. Others are invited to bring their own samples, thin sections, and/or images, and share your observations in the discussion. Magnetic fabrics of samples can be measured. Participants are encouraged to share thin section images and associated data using the StraboMicro app.
Workshop leads: Cristina Garcia-Lasanta (WWU), Bernie Housen (WWU), Peter Selkin (UWT). The anisotropy of magnetic susceptibility (AMS) and other anisotropic rock magnetic characteristics are useful proxies for petrofabric with a variety of structural applications, from determining strain histories in deformed rocks and sediments to reconstructing pluton emplacement. In this workshop, we will introduce you to the rock magnetic techniques commonly used to evaluate fabric, with an emphasis on fabrics of ultramafic rocks. The workshop will include an opportunity to collect and process magnetic fabric measurements and discussion of the benefits and limits of AMS and rock magnetism as structural tools.