13-1 Revised chronostratigraphy and provenance of Mesozoic-Cenozoic volcanogenic strata, Baja California Peninsula, Mexico: Implications for long-term basin development

Session: Toe to Toe: Cordilleran Systems from Trench to Retroarc Domains

Presenting Author:

Megan Mueller

Authors:

Mueller, Megan¹, Contreras-Lopez, Manuel², Lawton, Timothy³, Malkowski, Matthew⁴, Gutiérrez Trejo, Luis⁵, Stockli, Daniel⁶

Abstract:

The Triassic to present history of Guerrero-Alisitos-Vizcaino superterrane is preserved in the Baja California Peninsula, Mexico, with most models supporting Late Triassic subduction initiation; Early Jurassic to mid-Cretaceous oceanic arc magmatism, extension, and back-arc basin formation; mid-Cretaceous to Paleogene contraction, continental arc magmatism, and forearc basin deposition; and Neogene strike-slip deformation and Gulf of California opening. Although much of this existing tectonic framework is inferred from the age, depositional environments, and architecture of sedimentary deposits, few geochronologic and provenance data exist from these units. 

 

We present new zircon LA-ICP-MS U-Pb geochronology of tuffs and sandstone maximum depositional ages; Bayesian stratigraphic age modeling; sandstone petrography and detrital zircon sedimentary provenance data; and sediment accumulation and tectonic subsidence analysis. Updated chronostratigraphic ages from tuffs and sandstones of the San Hipolito and Eugenia formations significantly revise the stratigraphic column of the Vizcaino Peninsula. Samples from two locations of the Jurassic Eugenia Formation yielded mainly Late Cretaceous zircons with a few Cenozoic zircons, indicating a younger Late Cretaceous to Cenozoic depositional age. Miocene zircons recovered from the San Hipolito Formation amend its inferred age from Late Triassic–Early Jurassic to Miocene or younger. The Miocene section of the San Hipolito Formation, correlative with the Comondu Formation elsewhere on the Baja Peninsula, represents deposition in a transtensional basin. 

 

Mid- to Late Cretaceous forearc basin sandstone samples from Vizcaino Peninsula and the El Rosario area are dominated by mid-Cretaceous zircons sourced from the Peninsular Ranges Batholith. Sandstone compositions evolve from undissected to dissected arc provenance fields and increase in monocrystalline quartz and feldspar, which we interpret as arc unroofing. Stratigraphic age modeling from our revised chronostratigraphy of the Asuncion and Valle formations shows relatively rapid stratigraphic accumulation rates (100 to 1000 m/My) between ca. 108 to 92 Ma. These accelerated forearc sedimentation rates coincide with a peak in detrital zircon age modes in all basin strata and inferred arc unroofing, as well as with the previously proposed switch from extension to contraction within the overriding plate, migration of magmatism from the western oceanic belt to eastern continental belt, and rapid batholith exhumation. Our revised forearc basin analysis highlights the relationship between deformation regime, arc magmatism and batholith exhumation, and deep-water sedimentation.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

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