7-2 Lipid Biomarkers and Ostracods as Indicators of Late Pleistocene-Holocene Environmental Fluctuations of the Southern Chihuahua Desert, Mexico

Session: Earth Life Sciences across the Cordillera (Posters)

Poster Booth No.: 8

Presenting Author:

Claudia Chávez-Lara

Authors:

Chávez-Lara, Claudia Magali¹, Zhang, Yiming², Pancost, Richard³, Palacios-García, Betania⁴, García-Macedo, Kevin⁵, Ibarra-Morales, Diana⁶, Caballero, Margarita⁷

(1) Institute of Geophysics, UNAM, Mexico City, Distrito Federal, Mexico, (2) Organic Geochemistry Unit, University of Bristol, Bristol, United Kingdom, (3) Organic Geochemistry Unit, University of Bristol, Bristol, United Kingdom, (4) Posgrado en Ciencias de la Tierra, UNAM, Mexico City, Mexico, (5) Posgrado en Ciencias de la Tierra, UNAM, Mexico City, Mexico, (6) Institute of Geophysics, UNAM, Mexico City, Mexico, (7) Institute of Geophysics, UNAM, Mexico City, Mexico,

Abstract:

Understanding how ecological processes in arid regions respond to past hydroclimatic variability is essential for anticipating future change, yet long-term ecological evidence from deserts remains limited. The Chihuahua Desert of Mexico represents an important mid- to low-latitude arid zone influenced by monsoonal hydroclimate; however, the ecosystem evolution in this region since the Last Glacial is yet to be fully characterised. In this study, we investigate how lacustrine and surrounding terrestrial habitats from the Santa Clara Basin (Southern Chihuahua Desert) responded to hydrological changes during the Late Pleistocene and Holocene. Moreover, we compare our results with previously published lipid records in western and eastern regions of this desert and determine the influence of the North American Monsoon (NAM), the displacement of the Intertropical Convergence Zone (ITCZ) and El Niño Southern Oscillation (ENSO) activity in this arid region.

Overall, weak NAM is reflected during the late last glacial (18.7-14.7 cal ka BP) with high input of vascular plants of forests and grasslands. Moreover, high proportions of anaerobic bacteria reflect a scarcer vegetation environment during the Late Pleistocene. During the Early Holocene the NAM shifted northwards, and extreme drought is reflected by a sedimentary hiatus from 10.7 to 6.4 cal ka BP. During the mid Holocene, the NAM reached its maximum extension, but after 7 cal ka BP, monsoonal rainfall declined. These conditions are registered in the sedimentary record from 6.2 to 5.5 cal ka BP and represent the transitional period from a relatively restored lacustrine environment, with the highest productivity of Limnocytherina axalapasco, to an ephemeral lake with microbial adaptation to a drier environment. The last 5.4 cal ka represent the period of a much dryer environment (higher proportions of archaeol and sterols; lower BIT and GDGT-0) as a result of the southward migration of the ITCZ, and the modern vegetation dominated by xerophilous scrub possibly established. Winter precipitation influence due to enhanced ENSO activity is not as clear in the southern desert as in western and eastern areas. Our work reveals that the Southern Chihuahua Desert ecosystems have responded sensitively to hydroclimatic shifts since the Last Glacial, underscoring their vulnerability to future hydrological extremes such as droughts.

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

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