2004 Denver Annual Meeting (November 7–10, 2004)

Paper No. 15
Presentation Time: 8:00 AM-12:00 PM


DEROSE, Margie B., Department of Geological Sciences, California State Univ, Fullerton, 800 N. State College Blvd, Fullerton, CA 92834, KIRBY, Matthew E., Geological Sciences, California State Univ, Fullerton, Fullerton, CA 92834 and BIRD, Broxton W., Geological Sciences, California State Univ, Fullerton, 800 N. State College Blvd, Fullerton, CA 92834, mderose6@yahoo.com

There are very few lake records of past climate change in Southern California. As part of a research initiative to understand better the region’s baseline of natural climate variability, a series of lake research projects are being conducted throughout Southern California. One of the study lakes is Crystal Lake. Crystal Lake is a natural water body located in the San Gabriel Mountains of Southern California. The lake’s small drainage basin and direct recharge of water via precipitation run off, make the lake an ideal setting for recording a history of storm events. Based this reasoning, several cores (n=6) were extracted from Crystal Lake in the summer of 2003 to assess the lake’s sedimentological potential for paleoclimate studies, specifically paleo-storm activity. Total organic matter, total carbonate, mass magnetic susceptibility, and microscopic charcoal counts were measured on two lake sediment cores. In addition, a history of human activity, fire history, and precipitation data were obtained for the Crystal Lake area. Sediment age control was determined by correlating known anthropogenic disturbance and fire activity age data with measured sediment characteristics (i.e., charcoal and cement-produced, CaCO3 peaks). Using these correlations, we estimate a basal age of the longest core at less than 200 years BP. During this interval, six rapid sedimentation layers (RSL) were identified. Comparing regional fire activity, human development in the lake’s drainage basin, and precipitation data to the timing of the six RSL’s suggest that at least five RSL’s correlate to non-climate related disturbances such as human activity (i.e., construction of buildings) and fire occurrence (i.e., reduction in soil stability). As a result, it is concluded that Crystal Lake sediments deposited over the past 200 years record a complex history of drainage basin disturbances. Longer cores that pre-date human disturbance are required to deconvolve better the non-climate from the climate signal. In addition, it is necessary to separate fire-related RSL’s from precipitation-related RSL’s through careful evaluation of charcoal distribution.