28-3 Middle Miocene microfossils in the Gulf of California - original or reworked?

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 I)

Presenting Author:

Authors:

Abstract:

Outcrop and subsurface data on the western coast of the Gulf of California indicate sedimentation on marine environments during the Late Miocene, from the north, in the Salton Sea (7.4-6.09 Ma), near San Felipe (6.16-4.26 Ma), on the Puertecitos platform (<8-5.33 Ma), and southward, near Santa Rosalía (7.09-6.93 Ma).

Marine sedimentary rocks from the Late Miocene to Early Pliocene (5.6–4.9 Ma) are also found on Tiburón Island. The eastern Gulf coast contains clastic Miocene sediments (>8.5 Ma) but lacks marine outcrops. However, subsurface data show marine sedimentation in west-central Sonora from the Late Miocene to Early Pliocene, and in southern Sonora during the Late Miocene (11.8-8.6 Ma).

In these sections, microfossils from the early to middle Miocene (>11.6 Ma) have been reworked, as indicated by the co-occurrence of younger fossils.

Subsurface data from some basins in the Gulf of California reveal marine sedimentation from the Middle Miocene (approximately 12 Ma) to the present. Dinoflagellates and calcareous nannofossils in exploratory well samples indicate that shallow marine sedimentation in this area began in the Middle Miocene (ca. 12 Ma) and continued into the Recent.

These Middle Miocene fossils, reliably identified and without association with younger specimens, reflect the oldest marine sedimentation in the Proto-Gulf and are the source of the reworked marine fossils in regional Late Miocene to Pliocene sections.

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

doi: 10.1130/abs/2026CD-12478

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