HOLOCENE PALEOECOLOGY OF AN ESTUARY ON SANTA-ROSA-ISLAND, CALIFORNIA

The middle to late Holocene history and early Anglo-European settlemen t impacts on Santa Rosa Island, California, were studied through the a nalysis of sediments in a small estuarine marsh. A 5.4-m-long sediment core produced a stratigraphic and pollen record spanning the last 520 0 yr. Three major zones are distinguishable in the core. The lowermost zone (5200 to 3250 yr B.P.) represents a time of arid climate with pr edominantly marine sediment input and high Chenopodiaceae and Ambrosia pollen values. The intermediate zone (3250 yr B.P. to 1800 A.D.) is c haracterized by greater fresh water input and high values for Asterace ae and Cyperaceae pollen and charcoal particles. The uppermost zone (1 800 A.D. to present) documents the unprecedented erosion, sedimentatio n, and vegetation change that resulted from the introduction of large exotic herbivores and exotic plants to the island during Anglo-Europea n settlement. The identification of pollen grains of Torrey Pine (Pinu s torreyana) documents the persistence of this endemic species on the island throughout the middle to late Holocene. (C) 1994 University of Washington.