Jurassic volcanic and sedimentary rocks of the La Silla and Todos Santos Formations, Chiapas: Record of Nazas arc magmatism and rift-basin formation prior to opening of the Gulf of Mexico

Abstract

Stratigraphic relationships, detrital zircon provenance, U-Pb and 40 Ar/ 39 Ar geochronology, and trace element geochemistry in volcanic and sedimentary rocks of the Sierra homocline of central Chiapas near La Angostura reservoir in Mexico document an extensive pulse of Early-Middle Jurassic arc magmatism in rocks that overlie and intrude the Permian-Triassic Chiapas massif. Upper Jurassic rift-basin strata unconformably overlie the volcanic rocks and the massif. A Pliensbachian U-Pb (zircon) SHRIMP (sensitive high-resolution ion microprobe) age from porphyritic andesite (191.0 ± 3.0 Ma), Early to Middle Jurassic 40 Ar/ 39 Ar dates from andesitic dikes, U-Pb grain ages of detrital zircons in overlying strata (196-161 Ma), and previously reported K-Ar dates indicate that subduction-related magmatism occurred in the western portion of the Maya block from Early to latest Middle Jurassic time. We assign the volcanic rocks to the La Silla Formation, which correlates with the informal Pueblo Viejo andesite of the Cintalapa and Uzpanapa regions to the northwest. La Silla magmatism predates opening of the Gulf of Mexico Basin. The Todos Santos Formation, which overlies La Silla Formation, was deposited in extensional basins during the early stages of gulf opening. We recognize a lower El Diamante Member of the Todos Santos, consisting of red fl uvial sandstone, mudstone, and minor conglomerate containing primarily volcanic-lithic detritus; this member is characterized by a nearly unimodal Jurassic detrital zircon age population that indicates a Callovian or younger depositional age. Volcanic activity continued into the upper part of the El Diamante Member, but with a more mafi c character. We also recognize an upper member, which we term the Jericó Member. This member is characterized by thickly bedded, coarse-grained pebbly arkose intercalated with several thick intervals (tens of meters) of conglomerate and pebbly sandstone. Sandstone petrology indicates a source in the granitic rocks of the Chiapas massif, with a tendency to show deep-seated sources and a diverse zircon population in the upper part of the section. The upper Todos Santos Formation in the study area is gradational into the overlying San Ricardo Formation ( KimmeridgianTithonian ). The La Silla Formation was deposited in volcanic-complex environments, with a clear lack of differentiated vol canic rocks. Fluvial strata of the El Diamante Member were deposited in a mud-rich sinuous river system. The Jericó Member was deposited in large, sand-rich fl uvial systems, which probably represent deposits of riftaxis trunk streams; conglomerate facies were deposited in adjacent and interfi ngering alluvial fan systems. We suggest that the stratigraphic record of the western Maya block records a transition from volcanic arc to intra-arc basin and subsequently to rift basin during Pliensbachian to Oxfordian time.

U-Pb ages of igneous xenoliths in a salt diapir, La Popa basin: Implications for salt age in onshore Mexico salt basins

“…200 to ca. 165 Ma (Earliest Jurassic-middle Callovian; Barboza-Gudiño et al, 2008;Godínez-Urban et al, 2011;Rubio-Cisneros and Lawton, 2011;Lawton and Molina-Garza, 2014). The diapiric xenoliths described here, in addition to having a different geographic distribution than the Nazas rocks, are younger than volcanic rocks ascribed to the Note: Whole-rock major-element concentrations were determined by X-ray fluorescence spectroscopy at New Mexico State University, using a Rigaku ZSX wavelength-dispersive spectrograph equipped with an end-window Rh target X-ray tube; bdbelow detection limits.…”

Sucesión volcánica Jurásica en el área de Charcas, San Luis Potosí: Contribución al entendimiento del Arco Nazas en el noreste de México

“…Sin embargo, de forma general, se podría relacionar la génesis de este vulcanismo con la subducción de la placa Mezcalera bajo la margen paleopacífica de México durante el Jurásico Temprano y Medio (Dickinson y Lawton, 2001). Magmatismo de arco continental del Jurásico Inferior a Medio, se ha documentado en el área de Aramberri y valle del Huizachal (García-Obregón, 2007), así como en la Sierra de Chiapas, Chiapas (Godínez-Urban et al, 2011). En todos los casos, las sucesiones volcánicas presentan patrones multielementos típicos de magmas de arco continental.…”

“…Sin embargo, las rocas volcánicas de la Formación La Silla, Sierra de Chiapas, asociadas al Arco Nazas (Godínez-Urban et al, 2011), se caracterizan por patrones comparables a los de la sucesión volcánica bajo estudio, aunque las anomalías negativas de Sr y Ti son ausentes (Figura 8C).…”

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

“…La formación más antigua es La Silla, representada por una sucesión siliciclástica, vulcano-sedimentaria de ambiente continental, su contacto superior subyace con discordancia angular a la Formación Todos Santos y sobreyace de la misma forma a rocas del Pérmico o más antiguas. La edad de la Formación La Silla, dada por U-Pb de circones detríticos se ha fijado entre 196 -171 Ma (Godínez-Urban et al, 2012). Geocronología 40 Ar/ 39 Ar en diques de andesita que intrusionan a esta formación indican un magmatismo de 191.0 ± 3.0 Ma, que puede extenderse hasta 161 Ma.…”

“…Un cambio en el movimiento de placas pudo generar una posible convergencia de placas, con el emplazamiento de un arco magmático continental representado por los depósitos del ciclo vulcánico y sedimentario del Jurásico Inferior. En este evento geodinámico la etapa magmática félsica está documentada entre 198 a 178 Ma, representada por el Granito Magistral (Damon et al, 1981), la Formación Nazas en Charcas y Villa Juárez (Bartolini y Spell, 1997;Zavala et al, 2012;Lawton y Molina-Garza, 2014), la Formación Rodeo (Blickwede, 1981(Blickwede, , 2001López-Infanzón, 1986), la Formación La Silla (Godínez-Urban et al, 2012), Sierra de Omoa, Honduras (Horne et al, 1976) y en Ecuador y Perú (Baby et al, 2004). El final de este segundo ciclo de depósito está representado por su discordancia superior como un límite de secuencia.…”