Quimper Geological Society welcomes Leigh Tucker Marquis Richardson to lecture on garnet in beach sands of the Olympic Coast.
Lecture
Where are the Olympic Coast garnet sands coming from and how did they get there?
Washington State contains multiple beaches where garnet bearing sands are present, including the outer coast and within Puget Sound. The source of these garnets is unclear. To better understand where these garnets come from, we look inside them to investigate inclusion minerals. When garnets form in metamorphic environments, they can trap other minerals from their surroundings. These trapped minerals can give us pressure and temperature constraints to narrow down the source of the garnet. We can then compare results between garnet samples and their potential sources to their current locations. This information improves our understanding of how glaciers and rivers transported sediment during the last glaciation of the region. Our study also furthers a new technique of using garnet inclusions as tracers of where sediments originated.
About the Speakers
Leigh Tucker is a post-baccalaureate student at the University of Washington working towards a Bachelor of Science in Geology. Her undergraduate honors research extended the work started by Marquis Richardson, comparing sands from the Puget Sound and the Olympic Coast to determine if the garnets came from the same source. She recently interned with the USGS Earthquake Science Center on the development of an automated earthquake rupture mapping tool using machine learning and unmanned aerial vehicles. Leigh plans to pursue a graduate degree in volcanology after completing her BS in June 2025. When she isn’t studying, you can find Leigh baking, hiking, or reading to her granddaughter.
Marquis Richardson graduated from the University of Washington with a BS in Earth and Space Sciences: Geoscience. During his time there he investigated index mineral inclusions in garnet sands from Ruby and Rialto Beaches on the Olympic Coast (Washington). After graduation he hiked the Pacific Crest Trail and worked as a staff geologist for a geotechnical consulting firm before moving to restoration ecology work. He will be hiking the Continental Divide Trail over the summer of 2025 with plans to pursue graduate school after he returns.
Glaciers have shaped much of the Pacific Northwest’s landscape over the past 15,000 years. The Cordilleran ice sheet, repeated ice age floods, and expansive alpine glaciation have left their distinctive fingerprints on the topography of our region. Geologists and cartographers have been mapping and interpreting glacial landforms since the late 19th century. In the past decade, the Washington Geological Survey has created new maps that build upon this rich cartographic history by fusing older datasets and techniques with modern insights and technology, such as lidar.
Daniel Coe has been making maps of the Pacific Northwest for the past two decades. He currently serves as graphics editor for the