Coccolithophore and silicoflagellate records inmiddle-late holocene sediments from la paz basin (gulf of california): Paleoclimatic implications

摘要

La Paz Basin is located in the southwestern sector of the Gulf of California, near the mouth of the gulf, and so it is influenced by waters in the gulf and from the equatorial Pacific Ocean. Sediments obtained from the basin contain a sub-millennial paleoceanographic and paleoclimatic record for the past 7256 years. Downcore abundances of coccoliths and silicoflagellates suggest that high paleoproductivity conditions were common in the surface waters of the basin due to upwelling and gyres. It was especially obvious in the lower part of core K47, but mainly between 3495 and 2250 B.P. when taxa considered as high productivity and upwelling proxies (G. oceanica, "small" Gephyrocapsa, D. fibula var. robusta and O. pulchra) showed their highest abundances. These general conditions fluctuated throughout the time interval, with enhanced incursions of tropical waters, similar to those during an ENSO events, observed at 5528 B.P. and 4500 B.P. but especially at 3750 B.P. and in the upper part of the core.