21 Recent Advances in Cordilleran Tectonic Evolution—1: Paleozoic to Mesozoic (Posters)

Thursday, 16 May 2019
9:00 AM - 6:00 PM
Exhibit Hall B

PROVENANCE OF THE SIERRA DE SANTA ROSA FORMATION, SONORA, MEXICO: CONSTRAINTS FROM GEOCHEMSITRY AND U-PB GEOCHRONOLOGY

Paper number: 21-15
Program: Theme Sessions
Time: 9:00 AM – 6:00 PM

Authors

Abstract

Sedimentary rocks of Sierra de Santa Rosa Formation are well exposed in Caborca, Sonora, Mexico. Major oxides, trace elements, including rare earth elements, and U-Pb geochronology are carried out on siliciclastic rocks of Sierra de Santa Rosa Formation that crop out in Sierra del Alamo section to infer the characteristics of the source rocks. Major, trace elements and rare earth elements (REEs) concentrations vary significantly between sandstones and shales. Sandstones and shales show LREE enriched, flat HREE patterns with negative europium anomaly. The SiO2/Al2O3 and Al2O3/TiO2 ratios, chondrite normalized REE patterns, discriminant function diagram, bivariate and ternary plots indicate that the terrigenous materials were probably supplied from the weathered felsic and intermediate source rocks.

Detrital zircon U-Pb geochronology of Sierra de Santa Rosa Formation indicate two distinct zircon populations, Proterozoic and Triassic. Proterozoic zircons fall into three age populations (18% and 51%), with age ranges from 1751 to 1547 Ma, 1442 to 1115 Ma, and 1024 to 981 Ma. Triassic zircons well represented in Sierra de Santa Rosa Formation, with ages range from 251 to 205 Ma. These zircons occur between 48% and 71% of the analyzed samples. Zircon grains presented in the tuff samples of Sierra de Santa Rosa Formation indicate the Lower Jurassic age (199.7 to 190.4 Ma).

Geological Society of America Abstracts with Programs. Vol. 51, No. 4

doi: 10.1130/abs/2019CD-329652

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