Hydrological changes and paleoproductivity in the Gulf of California during middle and late Holocene and their relationship with ITCZ and North American Monsoon variability

This study investigates changes in precipitation patterns and variations in paleoproductivity in the tropical Pacific region associated with the North American Monsoon, Intertropical Convergence Zone (ITCZ) latitudinal migration, and changes in insolation during the middle and late Holocene. Major and trace element records (Al, Ba, C, K, Si and Ti) and Zr/Al and Ba/Al ratios in a core from Alfonso Basin, southern Gulf of California, are used as proxies of terrigenous input and bio-productivity. Records reveal an increase in precipitation and low bio-productivity ca. 6200 to 2400 cal yr BP, associated with the strengthening of monsoonal precipitation and northward shift of the ITCZ mean position in the eastern tropical Pacific. A multi-centennial drought from ca. 2400 to 1900 cal yr BP, and a dry and cold interval ca. 700 and 500 cal yr BP, are characterized by strong aeolian input and enhanced productivity, associated with diminution of the summer monsoonal precipitation and reduced insolation in the Northern Hemisphere and more southerly ITCZ position. Correlation of Alfonso Basin records with other records in the Gulf of California and the Pigmy and Cariaco basins in the Gulf of Mexico and central Atlantic provides constraints on NAM, ITCZ migration, and insolation-driven changes. (c) 2012 University of Washington. Published by Elsevier Inc. All rights reserved.