Developing a New Paradigm for the Mid-Cretaceous to Eocene North American Cordillera: An Obliquely Convergent Plate Margin
McCall, Idaho, USA | 18–25 August 2023
Strongly foliated orthogneiss, deformed by the western Idaho shear zone, exposed in the canyon country of Idaho. The view is to the south and the foliation dips steeply E, rotated from its pre-Miocene vertical orientation by normal faulting. Photo by Basil Tikoff.
University of Wisconsin–Madison, Dept. of Geoscience, Madison, Wisconsin, USA,
University of Nevada–Reno, Dept. of Geological Sciences, Reno, Nevada, USA,
Matthew A. Williams,
University of Calgary, Institute of Earth Sciences, Calgary, Canada,
Universidad Nacional Autónoma de México, Mexico City, Mexico,
- The Geological Society of America
- Divisions of The Geological Society of America (Geochronology; Geophysics and Geodynamics; Mineralogy; Geochemistry, Petrology, and Volcanology; Sedimentary Geology; Structural Geology and Tectonics)
- Canadian Tectonic Studies Group
- Geological Association of Canada Cordilleran Section
- Sociedad Geológica Mexicana
Description and Objectives
The issue of major right-lateral displacement throughout the North American Cordillera has been debated for 50 years. Paleomagnetic data from the western part of the Canadian Cordillera and some parts of the Pacific Northwest, during the interval ~110–40 Ma, have consistently suggested thousands of kilometers of northward displacement, while geological studies of fault movement indicate only hundreds. This discrepancy is unavoidable because faults tend to be on the margins of terranes, resulting in few unequivocal offset markers. Further debate includes the subduction polarity of the terranes with respect to the western margin of North America and the past size of the ocean basins that separated them. While this problem is most acute in the northern Cordillera, it has implications affect the entire North American margin. Recent data and analyses—including detrital zircons, mantle tomography, numerical modeling of plate motion, shear zone kinematics, and geochronology—have provided new insights. The objective of this Penrose Conference is to bring together a diverse community of open-minded scholars to discuss what is agreed upon and where future work is needed, but also to work collaboratively to evaluate how all the data sets can be reconciled into a coherent model for an obliquely convergent plate boundary.
The meeting will be held in Riggins and McCall, Idaho, USA. We will stay at the Best Western Hotel in Riggins, at the confluence of the main Salmon and Little Salmon rivers. This location will give us the opportunity to visit the Salmon River suture zone and the overprinting western Idaho shear zone. The remaining nights we will stay at the Quaker Hill Conference center in McCall, on the shores of Payette Lake. A second field trip day will explore the western Idaho shear zone in the glaciated, well-exposed mountains north of McCall.
The conference format will be a balance of oral presentations, poster presentations, and evening talks in preparation for field trips. Relative to other meetings, however, we will emphasize the working group discussions and report outs to the whole group. We will include a premeeting mentoring opportunity for early-career scientists. Attendees will be expected to observe the GSA Events Code of Conduct throughout the meeting. The conference will follow the COVID-19 protocols that GSA has established for meetings and field trips.
Meeting participants who are arriving by air will be shuttled from Boise Airport (BOI) to the conference venue on Friday, 18 August. It is approximately a three-hour ride by car. Day 1 of the conference (19 August) will focus on a broad overview of the problem, talks on the different methodologies, and a short introduction to the field trip on Day 2. A full-day tour of Salmon River suture zone—from North America, across the Salmon River belt, to the Wallowa terrane—will occur on Day 2, after which we will drive to McCall. Day 3 will begin with a morning session focused on the northern Cordillera, followed by an afternoon session on the southern Cordillera. Day 4 will start with the central Cordillera, and the afternoon session will be split, with half of the afternoon dedicated to a poster session to ensure that everyone has time to look at the posters. The rest of the afternoon will be background information to set the stage for the field trip on Day 5. Day 5 is the field trip to the western Idaho shear zone. Day 6 will include a jigsaw activity where we first organize by methodology discipline in breakout groups in the morning and then in the afternoon break up to talk by regions to recognize major issues within different sections of the Cordillera. Day 7 involves a morning of time-based, rather than place-based, breakout groups. The afternoon will include report out from groups, followed by a whole group discussion on what is agreed upon, what needs to be resolved, and organizational plans on how to continue working on this problem that necessarily crosses political divisions. We will leave for the Boise airport on the morning of Friday, 25 August.
Attendees and Estimated Costs
The anticipated registration fee will be announced at a later date and will cover seven nights of lodging, meals, transportation to/from Boise airport, transportation for field trips, and facility usage. Participants will be expected to pay for travel expenses from their home to the Boise airport and the return. However, we have funds allocated to support both the registration costs and the travel expenses of some participants, which will be prioritized toward students, early-career professionals, and participants from underrepresented groups in the geosciences. All participants will be expected to make their own travel arrangements to arrive at the Boise airport prior to 3 p.m. on 18 August and in the afternoon on 25 August. Alternatively, attendees may choose to provide their own transportation to McCall, and they will be picked up there on 18 August; these participants will be expected to use conference-provided transportation for the remainder of the meeting.
Applications and Registration
- Application period opens: 1 Dec. 2022
- Application deadline: 1 Mar. 2023
- Acceptance notices: 24 Mar. 2023
- Registration deadline: 14 Apr. 2023
GSA and the meeting conveners are committed to fostering diversity, equity, inclusion, and belonging in the geoscience community. We welcome and encourage applications from all gender identities, Black, Indigenous, Latinx, and People of Color, people with disabilities, LGBTQIA+ individuals, and other groups that are currently underrepresented within the earth-science community. We have dedicated funds to support conference participation for such individuals, as well as early-career researchers and students.
The conference will be limited to approximately 75 participants, and each participant will be expected to attend the full duration of the conference. To apply, please submit your application through the form on the meeting website:
As part of the application, you will be asked to prepare a brief statement of your interests and relevance of your work to the conference themes (300 words maximum), and a tentative title for a proposed presentation. Every participant will be expected to present at the conference. Applicants will be notified regarding attendance and presentation format (oral or poster) by or before 31 March 2023. Conference participants will be asked to submit full abstracts for presentations at the time of registration.
Please note that there will be sessions at the GSA Cordilleran Section Meeting in May 2023 that are thematically related to this Penrose Conference. These will include overview talks for new models recently proposed for North American Cordilleran margin. These sessions were designed to provide general background to facilitate synthesis on the Penrose meeting in Idaho.