Category: Pacific Northwest geology

2023-02-18 Chris Goldfinger — The Next Great Cascadia Earthquake – How Did We Get Here?

QMPGEOeditor1

Dr. Chris Goldfinger, explored the relation of offshore turbidites to the paleoseismic record of the Cascadia subduction zone.

During this presentation, Chris described that submarine paleoseismology is a multidisciplinary science that allows us to reconstruct earthquake histories extending back thousands of years. He provided information on the use of a variety of techniques, many originally developed for petroleum exploration, to study earthquake-generated submarine deposits (turbidites). By correlating these deposits over broad areas and examining their sedimentological characteristics, we gain insight into recurrence intervals, fault rupture lengths, event clustering, long-term strain histories, paleo-slip characteristics, and interactions between faults. He compared turbidite deposits associated with recent major earthquakes (e.g., 2004 Sumatra, 2016 New Zealand) with seismological records of those events is an important part of understanding ancient earthquakes.

He explained in Cascadia, a 10,000-year onshore-offshore record, developed in large part using submarine paleoseismology, has identified periods of earthquake clustering and quiescence. The pattern – clusters of 4-5 events separated by gaps of 700-1200 years – is unlikely to be randomly generated. Cascadia is broken into at least four segments that have differing recurrence intervals, decreasing from ~ 430-500 years in the north to ~ 240 years or less in the south. However, several lines of evidence suggest that inter-event time is not a good predicter of earthquake magnitude. Long turbidite records for Cascadia and the northern San Andreas Fault also reveal that the two faults have very similar event histories about 75% of the time, suggesting these major faults can trigger one other.

The Lecturer

Dr. Chris Goldfinger, emeritus professor at Oregon State University (OSU), is a marine geologist and geophysicist with a focus on great earthquakes and structure of plate boundary fault zones around the world. Chris has been involved in over 45 oceanographic cruises over the last 30 years, using many geophysical tools (deep submersibles, sidescan sonar, seismic reflection, etc.). He is currently working on great subduction earthquakes along the Cascadia, NE Japan, the Caribbean, and Sumatran margins, as well as the northern San Andreas Fault, where he uses the evidence for earthquakes found in deep-sea sediments.

Chris received his PhD from OSU in 1994. He is a Fellow of GSA and was the recipient of the 2016 GSA Kirk Bryan Award for Quaternary Geology. Windsurfing in the Columbia River Gorge and aerobatic flying are some of his favorite sports, as well as sailing to the south Pacific.

Chris suggested watching “Earthstorm” featured on Netflix for more on these topics.

2022-12-10 Marcia Bjornerud – Timefulness

QMPGEOeditor1

The Lecture

Developing and calibrating the geologic timescale — reconstructing Earth’s past from the raw rock record — is one of humanity’s greatest, but least appreciated, intellectual achievements.   But as a society, we are time illiterate, lacking a sense for the durations of the chapters in Earth’s history, the rates of change during previous intervals of climate instability, and the intrinsic timescales of ‘natural capital’ like groundwater systems.  This matters because environmental wrongs, social conflicts and existential malaise are all rooted in a distorted sense of humanity’s place in the history of the natural world.  Thinking like a geologist can simultaneously ground us and elevate us. Paradoxically, this Earth-bound, very physical science can yield transcendent insights.

Timefulness was longlisted for the 2019 PEN/E.O. Wilson Prize for Literary Science Writing and was a finalist for the 2018 the Phi Beta Kappa Award in Science, and the LA Times Book Prize in Science & Technology.

The Speaker
Marcia Bjornerud, Professor of Geosciences at Lawrence University in Wisconsin, is a structural geologist whose research focuses on the physics of earthquakes and mountain building. She combines field-based studies of bedrock geology with quantitative models of rock mechanics. She has done research in high arctic Norway (Svalbard) and Canada (Ellesmere Island), as well as mainland Norway, Italy, New Zealand, and the Lake Superior region.  Bjornerud is a Fellow of the Geological Society of America and has been a Fulbright Senior Scholar at the University of Oslo, Norway and University of Otago, New Zealand. A contributing writer to The New Yorker, Wired, the Wall Street Journal and the Los Angeles Times, she is also the author of several other books for popular audiences — Reading the Rocks: The Autobiography of the Earth and Geopedia: A Brief Compendium of Geologic Curiosities.

2022-10-15 Erin Donaghy, Revisiting stratigraphy of the Eocene to Miocene sedimentary peripheral rocks on the Olympic Peninsula, Washington

QMPGEOeditor3

The role of oceanic plateau collision in the geologic development of the Olympic Peninsula: testing geologic connection between Wrangell-St. Elias (AK) and Olympic (WA) National Parks.

The Pacific Northwest (PNW) has a long geologic history of seismic activity. Recent studies suggest the PNW experienced a collision ~50 million years ago (Ma, early Eocene) which resulted in an enormous oceanic plateau attaching itself to the west margin of the continent. That plateau is known fondly, as Siletzia.

On October 15, 2022, Erin Donaghy discussed what occurred after the accretion of Siletzia. She described the interbedded siltstone and sandstone turbidites in the deep marine environment. These rock strata are known as the peripheral sequence of the Olympic Peninsula and are thought to be part of the regional Tofino-Juan de Fuca forearc basin. These strata are divided into two distinct sections by the Lower Elwha fault (hanging wall = basalts (Silezia) and overlying sedimentary rocks; footwall = younger (Eocene to Miocene peripheral rocks). She explained how the correlation of Eocene deposits on the north side of the Olympic Peninsula and those on the south side is still not firmly established.

Erin and colleagues have been using new mapping and zircon geochronology of the north Olympics’ Blue Mountain Unit (BMU) to re-evaluate the basin formation in the context of Siletzia accretion. She explained how these new data suggest that continentally derived sediment flooded into the basin immediately before and after a major period of basaltic volcanism. Erin provided new interpretations of how the BMU reflects a period of marginal rifting after accretion. She also discussed the depositional setting for the Aldwell, Hoko River, and Makah Formations, which are younger than the docking event of Siletzia.

Erin and colleagues conducted more sampling this past summer (2022) in Wrangell-St. Elias National Park, AK, and the Olympic National Park, WA (September 2022). Ongoing high-precision uranium-lead zircon geochronology of interbedded volcanic rocks will provide more precise depositional ages for the sequences. Geologists think the Yakutat terrane, currently colliding with southeastern Alaska, may have originated as part of the Siletzia plateau offshore the PNW. She discussed the significance of the changing provenance of Eocene sedimentary rocks in the Tofino-Juan de Fuca basin within the context of a rifting oceanic plateau, migrating triple-junctions, and the possible northward translation of the Yakutat terrane during this time.

 

 

The Speaker:

Erin Donaghy is a sedimentologist and field geologist interested in studying basins that form along active convergent margins.

2012 – B.S. in Geology, Bucknell University (Lewisburg, PA); her initial interests included environmental geology and did aqueous geochemistry, before switching to Geology and wrote a thesis in sedimentology with Dr. Jeff Trop.

2015 – M.S. degree in Geology, Northern Arizona University (Flagstaff, AZ); she worked with Dr. Paul Umhoefer and studied the Eocene basin evolution of the Chumstick basin in central Washington. During graduate school she took time off to complete an internship with ConocoPhillips in Anchorage, AK and studied the structural and depositional evolution of basins offshore of the North Slope.

She then gained three years of professional experience as an exploration geologist in the energy industry, providing her the opportunity to study basins around the world. This included Deepwater Gulf of Mexico Exploration and Operated Wells, and the Global New Ventures Conventional teams.

current – PhD, Purdue University, Department of Earth, Atmospheric, and Planetary Sciences (West Lafayette, IN); her passion for teaching, mentoring, and research drove her to return to graduate school in Geology. Erin works with Dr. Michael Eddy and Dr. Kenneth Ridgway and uses the sedimentary record to tackle large-scale tectonic questions. She integrates both traditional field mapping methods and analytical methods in my research to constrain the temporal and lateral variations in depositional environments and provenance within sedimentary basins. This helps her piece together a detailed basin history in context of high-precision chronostratigraphy. She skillfully involves numerous undergraduates in both field and analytical lab work and mentored them through individual research projects where they have the opportunity to present at national level conferences.

Erin is well published, a great speaker, and is a geologist to follow into the future!