32-4 Tectonic Rotations from Paleomagnetic Data along the Eastern Margin of the Gulf of California

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:

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Abstract:

The eastern margin of the Gulf of California records a complex Neogene tectonic evolution associated with the transition from Farallon plate subduction beneath North America to subsequent oblique divergence between the Pacific and North America plates. In this study, paleomagnetic data from 15 volcanic and subvolcanic sites were analyzed to quantify vertical-axis block rotations during the proto-Gulf stage (12.5–6 Ma), complemented by additional sites compiled from the literature. Site-mean directions indicate significant clockwise rotations of up to ~88° in the Guaymas area at ca. 11 Ma, as well as minor counterclockwise rotations after 10 Ma. The results show that deformation was heterogeneous in time and space, with larger rotations concentrated near the coast and progressively smaller rotations inland. The occurrence of oblique faults, minor tilting, and variable block rotations suggests deformation controlled by interconnected strike-slip and normal faulting within transtensional shear zones. We propose a new kinematic model, termed Domainal Progressive-Integrated Transtension (DPIT), in which extension and shear are accommodated within discrete rotating domains rather than in uniform belts. This model accounts for the temporal decrease in rotation magnitudes, the prevalence of oblique faulting, and the compartmentalization of strain along the eastern margin of the Gulf of California.

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

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