32-9 Revealing New Insights into the Northern Gulf of California through Marine Magnetotelluric Data

Session: Recent Advances in the Gulf of California Oblique Rift: Offshore and Onshore Studies // Avances Recientes en el Rift Oblicuo del Golfo de California: Estudios Marinos y Terrestres (Part II)

Presenting Author:

Thalia Avilés-Esquivel

Authors:

Avilés-Esquivel, Thalia Anaid¹, Romo-Jones, José Manuel², Gómez-Treviño, Enrique³, Constable, Steven⁴, González-Escobar, Mario ⁵

(1) Geoaviles, Ensenada, Baja California, Mexico, (2) Centro de Investigación Científica y de Educación Superior de Ensenada, Baja California, Ensenada, Baja California, Mexico, (3) Centro de Investigación Científica y de Educación Superior de Ensenada, Baja California, Ensenada, Baja California, Mexico, (4) Institute of Geophysics and Planetary Physics, Scripps Institution of Oceanography, University of California San Diego, San Diego, California, USA, (5) Centro de Investigación Científica y de Educación Superior de Ensenada, Baja California, Ensenada, Baja California, Mexico,

Abstract:

The Gulf of California Rift (GCR) is a transtensional deformation system located between the Pacific and North American Plates. The GCR consists of right-lateral faults linked by pull-apart basins. However, the development of these extensional zones along the Gulf is not uniform. In the Southern Gulf, the Alarcón basin shows evidence of oceanic crust, whereas in the central Gulf, the Guaymas Basin contains basaltic intrusive sills emplaced within the sediments.

In the northern GCR, there is no evidence of oceanic crust. Most available data in this region are derived from reflection seismic surveys, which effectively image faults penetrating 5 to 7 km of sedimentary rocks. However, these data provide limited constraints on the deeper crustal structure.

This study presents new data on the subsedimentary crust to improve understanding of the crustal composition in the northern Gulf of California.

Data from 13 marine magnetotelluric (MT) soundings were used to construct a three-dimensional resistivity model of the Wagner Basin and the northern Consag Basin.

The model's resistivity distribution results are interpreted in two depth ranges. The shallow interval (0 to 6 km depth) is associated with the sedimentary layer and fault distribution. Low-resistivity zones within this depth range correlate with areas of a greater number of faults. Furthermore, conductive anomalies at depths of 3 to 6 km coincide with the locations of deep, active faults and zones of advective heat flow.

The deeper interval (10 to 20 km) reveals a 3–5 Ohm-m resistivity anomaly extending from the southern Wagner Basin to the northern Consag Basin.

This anomaly spatially coincides with earthquake hypocenters and low S-wave velocity anomalies, indicating the presence of a brittle-ductile boundary at approximately 20 km depth. The anomaly is also associated with low velocity values in the Consag Basin. Collectively, these observations suggest that the anomaly may correspond to a fractured region filled with fluids originating from the upper mantle.

The marine MT data interpreted in this work are the first of their kind to be measured in Mexico. The resulting resistivity distribution offers new, independent insights into the physical properties of the upper and middle crust in the northern Gulf of California Rift.

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

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