QRC members lead and participate in a wide range of disciplinary and interdisciplinary research projects from the study of past earth climates and glaciations to shifts in the geographic distributions and evolution of vegetation and faunal communities, to the evolution and dispersals of the genus Homo and the increasing scales of human modification of earth environments through the Holocene. QRC provides a venue for meeting and collaborating with scholars across Quaternary disciplines. We are also fortunate to be able to provide seed funding and small grants for member research projects. We are especially happy to support grad student and junior scholar research activities, much of which leads to larger, external funding from agencies like the National Science Foundation.
Evidence for liquefaction and flooding in the past 1,000 years along the Duwamish River, Seattle, Washington
Abstract: Geology along the Duwamish waterway, just south of downtown Seattle, provides preliminary clues to the city’s earthquake hazard. The banks of the dredged waterway expose the muddy deposits of an estuary that formerly drained Mount Rainier. Evidence for multiple episodes of liquefaction and unusual floods within the past 1,000 years have been pieced together from a few outcrops which record different aspects of the site’s history.
So far, inferred events include two episodes of liquefaction and two unusual floods from land or sea. All events post-date the large Seattle fault earthquake of 900—930 CE. Evidence for liquefaction consists of dikes and extrusive lenses of andesitic sand among muddy tidal deposits. The sand was likely vented from lahar runout deposits that underlie the tidal mud. Two persistent, horizontal silt layers observed in one outcrop suggest unusual flooding, either from Puget Sound or from upriver. Age control on the deposits comes in the form of radiocarbon ages of marsh plant fossils.
Additional dikes have been observed but have yet to be well-dated. Findings from this project may yield insights into Seattle’s earthquake and tsunami hazards.
Refining ages of tsunami deposits at Discovery Bay, Washington, using optically stimulated luminescence (OSL) dating
Abstract: A tidal marsh at the head of Discovery Bay has the longest and most important geologic record of tsunamis in Washington State. At least nine tsunamis have deposited fine sand layers in peaty tidal marsh sediments in the last 2,500 years. In addition, thinner sand layers, including one that may be from the 1964 Alaska tsunami, are interspersed among the thicker tsunami deposits. While radiocarbon dating has improved the timing of tsunami events at the site, there are outstanding questions that have not been resolved using this method. The proposed work seeks to determine timing of tsunami events with greater resolution to narrow down potential sources for each deposit, which could include Cascadia, local faults, tsunamigenic landslides (perhaps triggered by earthquakes), and distant source tsunamis. To further our knowledge of sources and recurrence, we propose to conduct a pilot study using optically stimulated luminescence (OSL) dating to test the applicability of the method to improving the ages of these deposits.
Abstract: A tidal marsh at the head of Discovery Bay has the longest and most important geologic record of tsunamis in Washington State. At least nine tsunamis have deposited fine sand layers in peaty tidal marsh sediments in the last 2,500 years. In addition, thinner sand layers, including one that may be from the 1964 Alaska tsunami, are interspersed among the thicker tsunami deposits. While radiocarbon dating has improved the timing of tsunami events at the site, there are outstanding questions that have not been resolved using this method. The proposed work seeks to determine timing of tsunami events with greater resolution to narrow down potential sources for each deposit, which could include Cascadia, local faults, tsunamigenic landslides (perhaps triggered by earthquakes), and distant source tsunamis. To further our knowledge of sources and recurrence, we propose to conduct a pilot study using optically stimulated luminescence (OSL) dating to test the applicability of the method to improving the ages of these deposits.