New data on the lithostratigraphy, detrital zircon and Nd isotope provenance, and paleogeographic setting of the El Antimonio Group, Sonora, Mexico

Abstract

The El Antimonio Group is herein proposed as a new lithostratigraphic unit that encompasses the Antimonio, Río Asunción, and Sierra de Santa Rosa Formations in a revised nomenclature from Lucas and Estep (1999b). The type section for the Antimonio, Río Asunción, and the lower part of the Sierra de Santa Rosa Formations is located in the Sierra del Álamo, whereas the representative upper part of the Sierra de Santa Rosa Formation is located in the mountains of same name in northwestern Sonora. The ~4.5-km-thick sedimentary succession of this group is abundantly fossiliferous, and its biostratigraphic age is constrained between the Late Permian and Early Jurassic. The 3.4-km-thick section that crops out in the Sierra del Álamo is divided into 14 unconformity-bounded sequences that are tens to hundreds of meters thick and grade from the base upward from a fl uvial to shallow marine conglomerate to open marine shale. The El Antimonio succession is correlated with several other Triassic and Jurassic sections that are known in Sonora, all of which are located south of the proposed trace of the Mojave-Sonora megashear. The closest Triassic and Lower Jurassic sections that are located north of the Mojave-Sonora megashear that we correlate with the El Antimonio are known in southern Nevada and southeastern California and include the Moenkopi, Virgin Limestone, Union Wash, Silverlake, and Fairview Valley Formations and the Kings sequence. On the basis of these proposed correlations, we suggest that the El Antimonio Group was deposited in an evolving

Insights into North American Paleogeography and Paleotectonics from U–Pb ages of detrital zircons in Mesozoic strata of the Colorado Plateau, USA

“…8, bottom) from strata transported northward into the Chinle-Dockum deposystem from sources distant \500 km to the south are dominated by a mixture of DZ grains derived from the Cordilleran magmatic arc (peak ages 220-245 Ma) and older grains derived from the Precambrian basement of the arc. Similar DZ populations are present in the forearc Antimonio Group (Gehrels and Stewart 1998) and Barranca Group (Gonzáléz-León et al 2005) deposited in northwest Sonora south of the trend of the Cordilleran arc (Fig. 7).…”

Las formaciones Gran Tesoro y Nazas: evolución de las secuencias Triásico Superior-Jurásico Inferior en México y su significado tectogenético

“…Estos ambientes pudieron ser desplazados lateralmente durante el Jurásico Medio (Megashear Mojave -Sonora). La parte inferior de la Formación Antimonio (Triásico) sobreyace en discordancia a rocas del Paleozoico (unidad II; González-León et al, 2005). El contacto entre las formaciones Río Asunción (Cárnico -Nórico) y Sierra de Santa Rosa (Hettangiano -Toarciano) también es discordante (con ausencia de Rético), y en el contexto regional esta última formación subyace con discordancia a rocas más jóvenes.…”

Genetic implications of new Sr and Nd isotopic data of the intrusive rocks from the Laramide Arc in Northern Sonora, Mexico.

“…A Mesozoic sequence (continental or deltaic sandstone and carbonaceous shale including some coal layers) was deposited unconformably (Barranca Formation) over the allochthonous rocks (Wilson and Rocha, 1949;Alencaster-De Cserna, 1961;Stewart et al, 1991). In the Caborca region (at El Antimonio area), the Triassic-Jurassic sedimentary rocks exhibit marine signature and were deposited over paleozoic platform rocks (White and Guiza, 1949;González-León, 1997;González-León et al, 2005). A Jurassic volcanic arc composed of andesites, tuffs and rhyolites, occasionally metamorphosed to greenschist facies, is well documented in the Sonoran desert between Santa Ana and Sonoyta (Anderson and Silver, 1979;Corona, 1979), as well as in Cananea (Valentine, 1936;Wodzicki, 1995).…”