7-14 Response of Benthic Foraminifera to Climatic and Oceanographic Variability during the Holocene in the Southern Gulf of California.

Session: Earth Life Sciences across the Cordillera (Posters)

Poster Booth No.: 20

Presenting Author:

Marysol Valdez Hernández

Authors:

Valdez Hernández, Marysol¹, Pérez-Cruz, Ligia², Urrutia-Fucugauchi, Jaime³, Venegas Ferrer, Rafael ⁴, Nava-Fernández, Xinantecatl Antonio⁵

(1) Laboratorio de Paleoceanografía y Paleoclimas, Instituto de Geofísica, Universidad Nacional Autónoma de México., Ciudad de México, Ciudad de México, Mexico, (2) Laboratorio de Paleoceanografía y Paleoclimas., Instituto de Geofísica, Universidad Nacional Autónoma de México., Ciudad de México, Ciudad de México, Mexico, (3) Instituto de Geofísica, Universidad Nacional Autónoma de México., Ciudad de México, Ciudad de México, Mexico, (4) Laboratorio de Paleoceanografía y Paleoclimas, Instituto de Geofísica, Universidad Nacional Autónoma de México., Ciudad de México, Ciudad de México, Mexico, (5) Laboratorio de Paleoceanografía y Paleoclimas, Instituto de Geofísica, Universidad Nacional Autónoma de México., Ciudad de México, Ciudad de México, Mexico,

Abstract:

In this study, the sedimentary sequence DIPAL IV-T-56 was analyzed and collected in 2011 aboard the R/V El Puma in the southwestern part of the Pescadero Basin in the Gulf of California of 591 m, underlying the Oxygen Minimum Zone (OMZ). The objective of this research is to reconstruct changes in oxygenation and productivity during the Holocene using benthic foraminiferal assemblages and organic carbon as proxies. The age model was constructed from eight AMS radiocarbon dates, defining a temporal framework for the sequence from ~10,900 to 130 cal yr BP. A total of 69 benthic foraminiferal species were identified. A Q-mode multivariate analysis was applied to the relative abundances of the foraminifera, defining three factors (assemblages). Based on the ecological affinities of the assemblages characterizing each factor and TOC fluctuations, four paleoceanographic and paleoclimatic scenarios are proposed for the Holocene: From ~10,900 to 10,200 cal yr BP, the proxies indicate low paleoproductivity and oxic bottom-water conditions. A reduction in the thickness of the OMZ is suggested, leading to homogeneous sediment deposition and a predominance of warm waters that allowed the proliferation of calcareous organisms. A second scenario, from ~9,910 to 5,800 cal yr BP, reveals low paleoproductivity and anoxic–microoxic bottom-water conditions. It is suggested that the factor controlling oxygenation during this period was an increased incursion of Pacific Intermediate Water (PIW) into the Gulf of California. This condition has also been reported in the Santa Barbara Basin, where it is associated with PIW production/ventilation. The third scenario, between ~5,800 to 3,380 cal yr BP, fluctuations in paleoproductivity are observed with pulses of high productivity (at ~3,900, ~3,700, and ~3,500 cal yr BP). These events may be related to mixing mechanisms, such as eddies and upwelling, in the study region, thereby promoting enhanced productivity. Bottom waters are inferred to have been microoxic–dysoxic. The final scenario, from ~3,380 to 130 cal yr BP, the highest productivity is inferred, resulting in anoxic–microxic conditions. Two intervals were identified in which benthic foraminifera are scarce, probably as a result of CaCO₃ dissolution due to very high productivity.

Geological Society of America Abstracts with Programs. Vol. 58, No. 3, 2026

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