EARLY HOLOCENE DECADAL-SCALE OCEAN VARIABILITY RECORDED IN GULF-OF-CALIFORNIA LAMINATED SEDIMENTS

Scanning electron microscope examination of Holocene laminated sedimen t from Guaymas Basin, Gulf of California, resolves up to five depositi onal events per year. Each lamina/sublamina of an early Holocene secti on of continuously laminated sediment was recorded from backscattered electron imagery photomosaic analysis. Diatom mat laminae, composed pr edominantly of Thalassiothrix longissima, are associated with early wi nter mixed diatom flora laminae. Mats are probably brought into the Gu lf with Pacific water during the summer, concentrated at the surface o r at the pycnocline, and then rapidly deposited in the early winter as water column stratification breaks down. Time series analysis of one similar to 300-year section from piston core JPC56 revealed significan t periodicities in the deposition of mat laminae at similar to 50 year s, similar to 11 years, and 22-24 years. An similar to 50-year cycle i n fish populations has been related to changing North Pacific ocean/at mosphere circulation. These Pacific-wide changes in circulation affect the currents dominant at the mouth of the Gulf. When the California C urrent is dominant, fewer diatom mats are imported into the Gulf, and when the north equatorial Pacific gyre is dominant, more are imported. The similar to 11-year, 22- to 24-year, and similar to 50-year cycles are all suggested to be influenced by solar cycles.