17 Paleoceanography and paleoclimate of the Gulf of California and how they resonate with the evolution of other marginal seas

This session features studies on the climatic and marine history of the Gulf of California and its connections to the global climate and ocean system, utilizing multidisciplinary geological, micropaleontological, geochemical, and numerical modeling proxies.

Thursday, 23 April 2026
9:30 AM - 12:00 PM
LMH, Deli

Bottom-water oxygenation and surface productivity variability in the Alfonso Basin, Gulf of California during the last 18,000 years inferred from planktonic and benthic foraminifera

Paper number: 17-4
Program: Technical Sessions
Time: 10:20 AM – 10:35 AM

Authors

Abstract

The oceanic dynamic of the Alfonso Basin, located in the southwestern Gulf of California, is sensitive to multiple forcing mechanisms. At present, the circulation patterns, productivity, and oxygenation conditions of the water column are seasonally influenced by the dynamics of a cyclonic eddy, associated with a reversible wind system associated with the North American Monsoon (NAM), latitudinal Intertropical Convergence Zone (ITCZ) migration, and interannually variability by the El Niño–Southern Oscillation (ENSO), among other factors. One of the most important characteristics of the Alfonso Basin is that its sediments preserve climatic signals with exceptional fidelity at different timescales beyond the instrumental record. 

This study aims to analyze changes in climate, hydrographic structure, and productivity in the Alfonso Basin during deglaciation and the Holocene, and to study planktonic and benthic foraminiferal assemblages in sediment cores from site DIPAL IV-P36. The chronology, based on eleven radiocarbon ages (AMS 14C), establishes an age-depth model spanning from ∼18,150 to 522 cal yr BP. Foraminiferal assemblages will be correlated with previously published geochemical data, including organic carbon, Ba/Al, Ti, and Zr/Al ratios. 

These proxies allow us to identify changes in the stratigraphic distribution of foraminiferal assemblages and geochemical proxies linked to major forcing mechanisms influencing climate variability over the last 18 kyr. This study provides important information on the productivity of surface and subsurface water masses and on oxygenation conditions. Furthermore, the data generated by this project will be compared with other paleoceanographic records from the Gulf of California and the eastern Pacific Ocean, enhancing understanding of long-term climate behavior and contributing to the improvement of global and climate change models. 

Geological Society of America Abstracts with Programs. Vol. 58, No. 3

doi: 10.1130/abs/2026CD-410988

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