DOCUMENTING CHANGES IN TERRESTRIAL SEDIMENT SOURCES TO MONTEREY BAY OVER DECADAL AND CENTENNIAL TIME SCALES

Continental shelves are important recorders of environmental change that occurs in the ocean or on land. Terrestrial environmental changes can alter sediment sources and transport pathways to the ocean. These changes in sediment sources can be caused by natural phenomena, such as climate change and/or seasonal weather patterns, as well as human activities, such as deforestation and urbanization. Historically, the Monterey Bay Shelf in central California has been fed by sediment sourced primarily through nearby fluvial processes. However, recent data suggests that there may have been a shift in sediment inputs from fluvial sources to sources derived from coastal environments within the last century. This project examines the natural changes in sediment sources to the Monterey Bay shelf sediment record through the late Holocene and contrasts those with recent anthropogenic changes in the last fifty years. To do this, we have analyzed sediment cores collected from the Monterey Bay Shelf as well as modern surface sediment samples taken from rivers and beaches in the region. Using the mineralogy of the surface samples, we have developed unique characteristics of the different source areas that can be compared to the minerology of the cores in order to reconstruct changes in sediment sources over time. This project will provide information about how human activities in the watershed and natural climate change variability influence sediment sources and the delivery of material from the land to the ocean. This understanding may assist in educating the public about the anthropogenic changes in coastal environments and how to mitigate the impacts from these activities.