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

Climate and Hydrological Cycle Connections in the Guaymas Basin, Gulf of California over the past 31,200 years: A Geochemical Approach

Paper number: 17-2
Program: Technical Sessions
Time: 9:50 AM – 10:05 AM

Authors

Abstract

Analyses of core sediments from Hole U1545A, recovered during IODP Expedition 385, record changes in the hydrological cycle at the Guaymas Basin (GB) over the past 31,200 years. We examined the uppermost 42 m of sediment from Core U1545A (Cores 385-U1545A-1H to 5H). The cores were analyzed using an energy-dispersive Avaatech X-ray fluorescence (XRF) core scanner (Rh X-ray tube). Elemental data were obtained at 2-cm resolution. Magnetic susceptibility measurements were taken at 2.5-cm intervals and conducted onboard the JOIDES Resolution. Natural Gamma Ray was also measured onboard. We established an age model through AMS radiocarbon dating of 17 bulk sediment samples. Our chemical proxies (Al, Ti, K, Fe, K/Al, K/Ti, Ti/Ca), together with magnetic susceptibility and NGR, indicate wetter conditions during the late Pleistocene compared to the Holocene in the region. Fluvial terrigenous input to the Guaymas Basin (GB) was significant during the late MIS3 and the Last Glacial Maximum (LGM), spanning ~31,200 to 29,000 cal yr BP, 26,000 to 18,000 cal yr BP, and ~13,500 to 12,800 cal yr BP. High magnetic susceptibility values are recorded between ~25,000 and 23,800 cal yr BP, with episodic peaks at ~22,000 and 19,000 cal yr BP. These wetter phases ended with a shift to drier conditions, suggesting increased aeolian input. We suggest that the southward displacement of the Intertropical Convergence Zone and the North Pacific High System influenced the GB. Expanded Northern Hemisphere ice sheets and an equatorward shift of the polar cell likely reduced NPH influence, contributing to increased humidity during cold intervals. These intervals include the LGM, Heinrich Events 2 and 1 (from ~26,000 to 25,000 cal yr BP and from ~17,000 to 16,000 cal yr BP), and the YD (between ~12,000 and 12,500 cal yr BP), which promoted terrigenous runoff. Proxy records indicate relatively minor fluctuations in fluvial terrigenous input throughout the Holocene. However, between ~7200 and 5800 cal yr BP, proxies indicate enhanced humidity, likely linked to a strengthened North American Monsoon (NAM). This would have promoted increased precipitation and river discharge into the basin. To date, records reflect a shift toward drier conditions, consistent with a weakening of NAM intensity and reduced continental moisture transport

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

doi: 10.1130/abs/2026CD-410921

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