Scanning electron microscope examination of Holocene laminated sediment from Guaymas Basin, Gulf of California, resolves up to five depositional events per year. Each lamina/sublamina of an early Holocene section of continuously laminated sediment was recorded from backscattered electron imagery photomosaic analysis. Diatom mat laminae, composed predominantly of Thalassiothrix longissima, are associated with early winter mixed diatom flora laminae. Mats are probably brought into the Gulf with Pacific water during the summer, concentrated at the surface or at the pycnocline, and then rapidly deposited in the early winter as water column stratification breaks down. Time series analysis of one ~300-year section from piston core JPC56 revealed significant periodicities in the deposition of mat laminae at ~50 years, ~11 years, and 22--24 years. An ~50-year cycle in fish populations has been related to changing North Pacific ocean/atmosphere circulation. These Pacific-wide changes in circulation affect the currents dominant at the mouth of the Gulf. When the California Current is dominant, fewer diatom mats are imported into the Gulf, and when the north equatorial Pacific gyre is dominant, more are imported. The ~11-year, 22- to 24-year, and ~50-year cycles are all suggested to be influenced by solar cycles.¿ 1997 American Geophysical Union