CORRELATION OF TEPHRA DEPOSITS IN LAKE SEDIMENT RECORDS, LAKE CLARK NATIONAL PARK, ALASKA

Lake Clark National Park (LACL) covers over four million acres of southwest Alaska, contains critical sockeye salmon habitat, numerous and regionally important archeological sites, and is the locus of several ongoing multidisciplinary quaternary studies (climate change, ecology glaciology, etc.). LACL is located along the northeast portion of the Aleutian Arc and adjacent to historically active Cook Inlet Volcanoes. Tephra studies are an integral part of understanding the dynamics, extent, cyclic occurrence, and hazards associated with volcanic events. Although numerous studies have cataloged tephra fall in other locations (Katmai, Anchorage, and Kenai Peninsula) the LACL region, north of many Aleutian volcanoes, remains relatively unstudied. Tephra layers represent a single instance in time and can be used to assemble a chronological framework for volcanic events as well as other studies requiring time specific information. Sediment cores obtained from eight small lakes located along a 40 mile transect (NE to SW along the Lake Clark valley) contain a sequence of visually distinguishable ashes which range from historic times to approximately 12,000 years. At least 6 of these appear to be correlative and it is likely that several can be positively correlated across the region, and in the larger lakes with additional analysis. Stratigraphic position, physical description, magnetic susceptibility, 14C age, petrography, and electron microprobe analysis is used to correlate ash layers across the LACL region. This study follows protocols that will allow these data to be used in future Alaska tephra studies. Correlations and chronological framework established in this study will aid ongoing geologic and biologic research in lacustrine systems and will serve as a guide for comparison to land-based geological, archeological, and paleoecological studies. Additionally, these data may prove useful in understanding the variability in subaerial and lacustrine records while improving the confidence of correlations between the two depositional environments.