INITIAL DRILL CORE RESULTS FROM LAKE ELSINORE’S CENTRAL BASIN: SEDIMENTOLOGY AND CHRONOLOGY SPANNING 11,200 CALENDAR YEARS

Southern California’s climate is highly sensitive to multi-scale, ocean-atmosphere interactions such as El-Nino Southern Oscillation (ENSO) and the Pacific-Decadal Oscillation (PDO). There are, however, very few, continuous Holocene, high-resolution terrestrial records from Southern California from which the history of these climate phenomena can be inferred. Here, we present the initial results from three ~10 meter drill cores extracted from the center basin of Lake Elsinore in November 2003. In addition to basic sediment descriptions, a variety of initial sedimentological analyses have been measured at 1 cm intervals including mass magnetic susceptibility, total organic matter, and total carbonate. At present, twenty-eight AMS 14C dates provide excellent age control. Basal ages from the 2 cores extracted from the lake’s deepest basin are: 8,100 cy BP (9.5 m total length) and 9,000 cy BP (11.0 m total length); the third core, from a slightly less deep “paleo-deltaic” setting, is dated at 11,200 cy BP (10.0 m total length). Lithologically, these cores are characterized by a variety of distinctive features including rapid sedimentation layers (RSL’s: storm deposits or seismites?), abrupt sediment transitions (rapid lake-level change?), and intervals of homogenous, occasionally laminated sediment (stable lake levels?). As an initial interpretation, we divide the Lake Elsinore sediment-climate record into three general intervals: a wet, climatically stable early Holocene, a mid-Holocene transition demarcated by an abundance of RSL’s, and a highly variable late Holocene climate characterized by rapid lake-level changes (i.e., very dry or very wet; an ENSO-dominated climate regime?). These general interpretations will become more specific as additional analyses (e.g., stable oxygen and carbon isotopes on calcite; C:N ratios; pollen; diatoms; ostracods, etc.) and dates are added. Nonetheless, these initial results demonstrate the exceptional potential that Lake Elsinore sediments contain for reconstructing Holocene climate variability, such as the evolution of ENSO and the PDO, in Southern California.