Knowledge Bank

The intention behind this research was to better understand the grain size of fourteen previously untested cores from the Southern Cascadia Subduction Zone. A better understanding of grain size from this area could be useful in an improved understanding of hazards associated with seismic activity. Another goal of this research was to lay groundwork for more research to be done in the future. Samples were collected from the United States Geological Survey Coastal and Marine Science Center core repository in Santa Cruz, California. One to two gram samples were collected every two centimeters from cores JPC 1, 4, 5, 6, 31, 32, 34, 35, 36, 37, 38, 39, 40, and 41 and then analyzed for grain size at The Ohio State University Marine Geology and Geohazards Laboratory. Grain size was determined with a Horiba Partica LA – 960V2 laser diffraction grain size analyzer. The data was plotted in standard ternary plots, percent-finer graphs, and downcore grain size graphs for each core. The overwhelming majority of cores were silt-dominated. There were also several instances of fining upward in the downcore grain size graphs for many cores. This suggests possible records of sediment gravity deposits in those areas.