Abstracts of the 9th International Conference SIS'01 RARE EARTH ELEMENTS VERTICAL PROFILES IN PB- 210 AGE-DATED SEDIMENT CORES FROM SOUTHWESTERN GULF OF CALIFORNIA St. Kalmykov1, E. Shumilin2, E. Nava-Sanchez2, D.Yu. Sapozhnikov3, A.P. Rodriguez Castaneda2, D. Gorsline4, Yu.A. Sapozhnikov1 1 • Moscow State University, Moscow, Russia 2 • Interdisciplinary Marine Science Center, La Paz, Baja California Sur, Mexico 3 • Vernadsky Institute of Geochemistry and Analytical Chemistry, Moscow, Russia 4 • University of Southern California, Los Angeles, USA Vertical profils of rare earth elements (REEs) were examined in four 210Pb age- dated sediment cores collected from the shelf and slope of the southern Baja California peninsula (areas in front of Santa Rosalia, Loreto, El Coyote and San Juan de La Costa) using instrumental neutron activation analysis technique. No significant anthropogenic impact on the content of REEs in sediments was found. Some variations of REEs concentrations seen down cores probably have natural origins, and are attributed to temporal changes of the ratio of terrigenic and marine biogenic supplies of REEs from the water column to the deposits of the sea floor. Shale-normalized REEs data for sediment cores from Santa Rosalia area and from the Loreto Bay manifest a positive Eu anomaly in comparison with other REEs which probably reflects some influence of hydrothermal activity from the bottom of the adjacent part of the Gulf of California in the past or at the present time. In contrast, in laminated sediment cores taken in front of the El Coyote fan- delta and San Juan de La Costa phosphorite mine, and of the La Paz Bay, strong minima of the shale-normalized ratios for Eu were registered reflecting the periodic existence of depositional conditions with elevated contributions of Eu-depleted material in the coastal suspended particulate matter. SK01K0227 78.