3 Geomorphological, Hydrologic, and Geothermal investigations of basin aquifers in Baja California Sur (BCS), Mexico
The session will explore BCS basins, focusing on groundwater storage, evaporation, runoff and transport mechanisms, featuring experts on thermal and shallow groundwater interactions, soil mapping for hydrological planning, geomorphology, and human impacts on water balance.
Wednesday, 22 April 2026
8:00 AM - 12:00 PM
LMH, Isla Carmen
Coastal Geothermal Systems from Southern Baja California: Insights from Fluid Geochemistry
Paper number: 3-9
Program: Technical Sessions
Time: 10:05 AM – 10:20 AM
Authors
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Loic Peiffer Presenting AuthorCentro de Investigacion Cientifica y de Educacion Superior de Ensenada , La Paz, B.C.S.
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Claudio InguaggiatoCentro de Investigacion Cientifica y de Educacion Superior de Ensenada , Ensenada, Baja California
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Jobst WurlUniversidad Autonoma de Baja California Sur, La Paz, B.C.S.
Abstract
The Baja California peninsula (Mexico) forms the western edge of the active Gulf of California rift system, an area marked by significant seismicity and numerous geothermal sites. In this study, we focused on the geochemistry of thermal fluids from the southern tip of the peninsula, specifically within the Los Cabos Block (LCB). Fieldwork concentrated on coastal thermal manifestations in the towns of Buenavista and El Sargento, with additional inland sites broadening the regional perspective. Key objectives include characterizing water-rock interactions and other processes controlling fluid compositions, refining solute geothermometry estimates through detailed geochemical modeling, and investigating fluid origins in relation to tectonics and regional shear-wave velocity anomalies. Findings reveal that geothermal systems in this area are tectonically controlled, with fluid circulation along deep regional faults cutting through the granitic basement. Coastal mixing between thermal fluids and seawater is demonstrated by major ion chemistry and stable isotope signatures (δ¹⁸O–δD). Geochemical reconstructions show distinct fluid types: a low-salinity fluid at Buenavista and a highly saline fluid at El Sargento, reflecting different thermal regimes at depth (101–122 °C vs. 212–220 °C, respectively). Gas analyses reveal some of the lowest helium isotopic ratios (0.07–0.95 Ra) reported from the Baja California peninsula, indicating a predominantly crustal helium source. Shear-wave tomography identifies two distinct low-velocity zones, one in the crust and another in the upper mantle, supporting the hypothesis that fluid heating is driven by lower-crustal flow influenced by strong topographic gradients along the rifted margin.
Geological Society of America Abstracts with Programs. Vol. 58, No. 3
doi: 10.1130/abs/2026CD-410811
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