The late Atokan (Moscovian, Pennsylvanian) chaetetid accumulations of Sierra Agua Verde, Sonora (NW Mexico): composition, facies and palaeoenvironmental signals

Abstract

The La Joya Formation of the Sierra Agua Verde, Sonora (NW Mexico) is late Atokan in age, equivalent to the early late Moscovian (Podolskian) and fusulinid biozone A3. In this alternance of cherty limestones and thin shaly beds, fusulinellid or anchicodiacean ('phylloid algae') wackestones-packstones and crinoidal rudstones-grainstones are the predominant microfacies, but chaetetid boundstones are conspicuous. These chaetetid occurrences of the Sierra Agua Verde are compared with the accumulations of Arizona, Texas, Kansas and Nevada (USA), and the Cantabric Cordillera (Spain). In Sonora, the environments with chaetetids were quiet, and located below wave base. Shallower facies with staffellids and Komia generally top the chaetetids. Because of the associated micritic deposits, the chaetetids have inhabited probably a soft or firm substrate. As a result of the disphotic-aphotic reconstructed environments, the possible symbionts of the chaetetids are more probably heterotrophic bacteria than autotrophic algae. The most comparable ecological conditions exist in the Atokan Marble Falls Formation of central Texas (USA). Chaetetids are not mentioned in the southern suspect terranes of Mexico, but were possibly present because these regions were located along the probable migration way to Peru, the southernmost area where Pennsylvanian chaetetids are known.

Crinoides (Echinodermata: Crinoidea) del Pensilvánico de sierra Las Mesteñas, NE de Sonora, México

“…En México se ha citado para la Formación Del Monte, de edad pensilvánica, en Calnali, Hidalgo (Buitrón-Sánchez et al, 1987), para el Virgiliano (Pensilvánico Superior) de San Salvador Patlanoaya, Puebla (Velasco-de León y Buitrón-Sánchez, 1992), para el Pérmico inferior de la Formación Guacamaya de Pemuxco, Hidalgo (Arellano-Gil et al, 1998). C. jucundus también se reporta para el Pérmico medio de Cerros Los Monos, Sonora (Buitrón-Sánchez, Almazán-Vázquez et al, 2007); igualmente, para el Pensilvánico Medio-Superior (Desmoinesiano-Misuriano) de Cerros El Tule, Sonora (Buitrón-Sánchez et al, 2008, 2012.…”

“…UU. (Moore y Jeffords, 1968), del Pensilvánico Superior (Misuriano-Virgiliano) de San Salvador Patlanoaya, Puebla (Esquivel-Macías et al, 2000), del Pérmico inferior (Wolfcampiano-Leonardiano) de la Formación Tuzancoa (Arellano-Gil et al, 1998), del Pérmico medio de la Formación Olinalá/Los Arcos, en Olinalá, Guerrero (González-Arreola et al, 1994) y del Pérmico medio de Cerros Los Monos en Caborca, Sonora (Buitrón-Sánchez, Almazán-Vázquez et al, 2007).…”

A new plate-like hypercalcified chaetetid demosponge (Loiscupula bachendensi gen. nov. sp. nov) from the Cantabrian Zone (Moscovian, Pennsylvanian, NW Spain)

“…Chaetetids are commonly interpreted to have inhabited very shallow-water subtidal environments, close to intertidal depths where the water is somewhat agitated (Connolly et al, 1989;Wahlman, 2002). However, these organisms were probably able to thrive over a range of depths, and chaetetid accumulations have been reported at paleowater depths of approximately 100 m in Sonora, Mexico (Almazán-Vázquez et al, 2007).…”

“…Early lithification of the substrate is also supported by the upper non-erosive hummocky irregular topography of the Loiscupula occurrence. As pointed by Almazán-Vázquez et al (2007), such substrates would be favoured by relative strong hydrodynamic conditions that permitted rapid cementation of the granular sediments.…”

Evolution and Geological Significance of Larger Benthic Foraminifera

“…Their fossil shells occur in light grey, shallow-water limestones or calcareous shales. They are associated with phylloid algae, corals, chaetetids, crinoids, bryozoans, and brachiopods (Thompson, 1964;Ross, 1965Ross, , 1967Ross, , 1969Stevens, 1971;Wilson, 1975;Haynes, 1981;Gallagher, 1998;Wahlman, 2002;Wahlman and Konovalova, 2002;Almazán et al, 2007, Davydov, 2011. This type of benthic carbonate production prevails in shallow, oligotrophic, warm and sunlit environments, with minimal siliclastic input, and with production rates highest in very shallow waters above a maximum depth of 25-30m (Weidlich, 2007).…”