34 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 (Posters)
This session highlights recent research on the Gulf of California–Salton Trough plate boundary from ~12 Ma to today. We welcome terrestrial and marine studies involving tectonics, basin analysis, volcanology, sedimentology, and more. English or Spanish.
Friday, 24 April 2026
8:00 AM - 5:30 PM
LMH, 5th Floor Chapel
From Marine Basement to Caldera Fill: Stratigraphic Framework for El Azufre Canyon, Aguajito Caldera (Baja California Sur, Mexico)
Paper number: 34-8
Program: Technical Sessions
Time: 8:00 AM – 8:00 AM
Authors
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Antonio Pola Presenting AuthorEscuela Nacional de Estudios Superiores - Unidad Morelia. Universidad Nacional Autónoma de México, Morelia, Michoacán
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Pedro Pacheco ValdovinosEscuela Nacional de Estudios Superiores - Unidad Morelia. Universidad Nacional Autónoma de México, Morelia, Michoacán
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Hugo SerenoEscuela Nacional de Estudios Superiores - Unidad Morelia. Universidad Nacional Autónoma de México, Morelia, Michoacán
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José Macías VázquezInstituto de Geofísica - Unidad Michoacán. Universidad Nacional Autónoma de México, Morelia, Michoacán
Abstract
El Azufre Canyon preserves one of the most complete, laterally traceable stratigraphic transects through the Aguajito caldera succession, capturing the transition from a marine volcano-sedimentary basement to syn-caldera pyroclastic infill and post-caldera volcanic–volcaniclastic cover. The pre-caldera section records shallow-marine deposition dominated by siltstones and fossiliferous sandstones, locally interrupted by a lithic-rich pyroclastic unit and a thin, white pyroclastic-flow marker bed. This sedimentary package is capped by submarine lava flows expressed as slab-structured facies and hyaloclastite, forming the immediate substrate for the caldera-forming ignimbrite, and preserving evidence of paleotopographic and/or structural relief along the basal contact.
The syn-caldera sequence corresponds to the Aguajito Ignimbrite and is subdivided into ten mappable stratigraphic units (U1–U10) recognized by systematic changes in color, internal architecture, and pumice/fiamme and lithic abundance. A basal massive pyroclastic-flow unit (U1) is overlain by a thick package of structured pyroclastic surges (U2) characterized by laminations, crossbedding, dune forms, and clast alignment, providing the most robust correlation interval across the canyon. Above, a pale, non-welded to weakly welded, pseudo-bedded unit (U3) transitions into a massive unit with conspicuous degassing/elutriation pipes (U4). The upper ignimbrite includes a locally preserved, strongly altered white unit (U5), a distinctive very welded violet unit with large fiamme and cross-stratification (U6), and a thin cap (U7–U10) of centimeter- to meter-scale welded to moderately welded units.
Post-caldera deposits record rapid landscape reworking and renewed volcanism, beginning with debris-flow (lahar) deposits, followed by blocky lava flows, thick effusive lavas, and younger channelized debris-flow and reworked deposits. This stratigraphic framework provides a basis for section-to-section correlation, geologic mapping, and reconstruction of caldera evolution in a marine-influenced volcanic setting.
Geological Society of America Abstracts with Programs. Vol. 58, No. 3
doi: 10.1130/abs/2026CD-410983
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