23-4 Late Quaternary Deformation History of the Coastal Ixtapa Fault, Northern Mexican Subduction Zone

Session: Subduction Zones and Their Volcanic Arcs: Initiation and Evolution, Structure, Metamorphism, Magmatism (Posters)

Poster Booth No.: 18

Presenting Author:

Elizabeth Davis

Authors:

Davis, Elizabeth J¹, Ramírez-Herrera, Maria-Teresa², Rodrigues, Kathleen³

(1) Instituto de Geografía, Universidad Nacional Autónoma de México, Ciudad de México, Mexico; Department of Earth and Space Sciences, University of Washington, Seattle, Washington, USA, (2) Instituto de Geografía, Universidad Nacional Autónoma de México, Ciudad de México, Mexico, (3) Division of Earth and Ecosystem Sciences, Desert Research Institute, Reno, NV, USA,

Abstract:

The Ixtapa Fault bounds the southern margin of the Puerto Vallarta graben at the northern edge of the Jalisco Block within the Mexican Subduction Zone.  Despite its structural importance, the fault’s Quaternary activity and role in forearc deformation have not been previously demonstrated.  We present results of geomorphic mapping from high-resolution LiDAR, detailed field stratigraphy, and infrared stimulated luminescence (IRSL) dating to evaluate the timing and magnitude of fault-related deformation.  Four fluvial terraces parallel the Ixtapa Fault and the Rio Mascota, recording phases of both incision and aggradation on both the upthrown and downthrown sides of the fault.  IRSL ages from terrace deposits constrain late Quaternary uplift and incision histories, bracketing the latest uplift to between 1.5 +/- 0.16 ka and 22.2 +/- 2.2 ka.  Vertical offsets imply long-term deformation rates consistent with uplift rates elsewhere along the Mexican forearc.  These results provide the first quantitative evidence of late Quaternary activity of the Ixtapa Fault and suggest that distributed normal faulting contributes to the ongoing forearc uplift and coastal deformation of the northern Jalisco Block.

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

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