Cambrian Stratigraphy of San José de Gracia, Sonora, Mexico: El Gavilán Formation, a new lithostratigraphic unit of middle Cambrian open shelf environment

Francisco Javier Cuen-Romero, José Eduardo Valdez-Holguín*, Blanca Estela Buitrón, Rogelio Monreal, Frederick Sundberg, Alejandra Montijo-González, Ismael Minjarez-Sosa

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

15 Scopus citations

Abstract

An approximately 600 m interval of Cambrian strata is exposed near the town of San José de Gracia, Sonora, Mexico. This succession is divided into four formations, one of which is proposed here as a new formal stratigraphic unit: El Gavilán Formation, following the rules of the North American Commission on Stratigraphic Nomenclature. The new nomenclature reflects substantial lithologic differences, particularly in the middle Cambrian strata in comparison with other Cambrian rocks exposed in other parts of the state. The Proveedora Formation consists of bioturbated, fine-grained quartz arenite with ichnofossils; the Buelna Formation consists of interbedded limestone and sandstone, with abundant trilobites of either the ?Bristolia mohavensis or ?Bristolia insolens Zone (Series 2?, Stage 4?); the Cerro Prieto Formation is a highly recrystallized oolitic limestone with fragments of ?Amecephalus arrojosensis at the base, suggesting the A. arrojosensis Biozone (Series 2?; Stage 4?); and the El Gavilán Formation consists of interbedded limestone and intensely fractured red shale, with abundant fauna of the upper part of the Mexicella mexicana Zone, Albertella highlandensis Subzone, Ptychagnostus praecurrens Zone (open shelf) (Series 3?, Stage 5?). The Cambrian rocks of Sonora were deposited in the occidental part of the North American craton during the early and middle Cambrian, when Laurentia must have been constituted by terrestrial masses near the paleoequator, aligned in an east-west direction, providing the right conditions for an abundant invertebrate marine fauna.

Original languageEnglish
Pages (from-to)429-441
Number of pages13
JournalBoletin de la Sociedad Geologica Mexicana
Volume68
Issue number3
DOIs
StatePublished - 2016

Bibliographical note

Funding Information:
The authors wish to thank Dr. Silvia Martínez Retama, Head of the Department of Geology at the Universidad de Sonora, and Dr. Elena Centeno García, Director of the Institute of Geology, UNAM, for their support in conducting this research. Francisco Cuen acknowledges the Posgrado en Biocencias (DICTUS-UNISON) for providing the facilities to carry out this research and the financial and technical support of CONACYT. We greatly appreciate the financial support provided by CONACYT grants No. 165826, 235970 and ECOS Francia-México No. 229494. We express our sincere thanks to Dr. Sara Alicia Quiroz Barroso (UNAM) and Dr. Matilde S. Beresi (CONICET-CCT) for the revision of this manuscript.

Keywords

  • Cambrian
  • Mexico
  • Sonora
  • Stratigraphy

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