34-3 The Oldest Exposed Marine Sediments in the San José del Cabo Basin, Southern Baja California Peninsula

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 (Posters)

Poster Booth No.: 3

Presenting Author:

Daniel Cota Ramírez

Authors:

Cota Ramírez, Daniel¹, Schwennicke, Tobias², Plata Hernández, Elvia³, Ramos Rodríguez, José Alejandro⁴, Walde, Michel Alain⁵

(1) Departamento Académico de Ciencias Marinas y Costeras, Universidad Autónoma de Baja California Sur, La Paz, Baja California Sur, Mexico, (2) Departamento Académico de Ciencias de la Tierra, Universidad Autónoma de Baja California Sur, La Paz, Baja California Sur, Mexico, (3) Departamento Académico de Ciencias de la Tierra, Universidad Autónoma de Baja California Sur, La Paz, Baja California Sur, Mexico, (4) Departamento Académico de Ciencias Marinas y Costeras, Universidad Autónoma de Baja California Sur, La Paz, Baja California Sur, Mexico, (5) Departement Umweltwissenschaften, Universität Basel, Basel, Basel-Stadt, Switzerland,

Abstract:

The San José del Cabo Basin owes its origin to the formation of the Gulf of California. Its basin fill consists of marine and terrestrial sedimentary rocks, comprising various geological formations ranging in age from upper Miocene to Pleistocene, in addition to Holocene deposits. The objective of this study was to identify the depositional environment and age of the marine sediments of the Trinidad Formation at Cerro (hill) Corona, located in the northern part of the basin. For this purpose, a 120-m stratigraphic section was measured. In general, sandstone, mudstone, and conglomerate crop out at this locality, reflecting depositional environments ranging from below fair-weather wave base to coastal-deltaic. A mudstone-dominated package containing calcareous nannofossils is intercalated in the middle part of the section. Although poorly preserved due to diagenetic processes, the following species were recognized: Discoaster berggrenii, D. quinqueramus, D. bellus, D. newellii, D. gemmulatus, D. blackstockae, D. asymmetricus, D. brouweri, D. hexaramus, D. variabilis, D. prolixus, and D. vinsonii. The age is constrained by the appearance of D. newellii in the lower NN11a zone (8.229 Ma), and the concurrence of the disappearance of D. bellus and the appearance of D. hexaramus in the lower NN11a zone (8.109 Ma). This suggests an age of ca. 8.2–8.1 Ma (late Tortonian) for the strata at Cerro Corona. To date, this is the oldest age reported for the Trinidad Formation in the San José del Cabo Basin.

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

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