Cambrian sponge spicules and Chancelloriid sclerites from the Argentine Precordillera : a Review

Spicules of sponges and sclerites of chancelloriids have been collected from in situ Cambrian sections of the La Laja Formation (San Juan Precordillera). They have also been collected from carbonate olistoliths, which were emplaced from the Cambrian units in the Early Ordovician Los Sombreros Formation (San Juan Precordillera) and Empozada Formation (Mendoza Precordillera). The Cambrian La Laja Formation sequences were deposited in a shallow carbonate platform in the eastern part of the Precordillera. The Cambrian carbonate rocks, which make up the olistoliths in the Los Sombreros and Empozada Formations, record deposition in the slope environments which developed in the western Precordillera. Cambrian Porifera and sponge-like chancelloriid assemblages are known mainly from fragments of skeletal nets, dissociated spicules and sclerites, which enable us to define two assemblages. The first assemblage of spicules was defined from the upper Lower to Middle Cambrian sequences of the La Laja Formation. This assemblage consists of a variety of stauractines and sclerites of Chancelloria WALCOTT. The family Protospongiidae is represented by triradiate prodianes, pentactines and hexactines, all belonging to Kiwetinokia WALCOTT. The second assemblage, which consists of isolated hexactines, pentactines, monaxons and skeletal nets, was defined in the Cambrian derived olistholiths of the Los Sombreros and Empozada Formations. Early hexactinellid Protospongiidae with body preservation (Diagoniella ? and Kiwetinokia) also occur. Demosponges have a very limited record in the Cambrian of the Precordillera. Anthaspidellid sponges had been reported from the La Laja Formation and now from the San Martín olistolith (Empozada Formation). The occurrences of these two assemblages of spicules and sclerites in both the Cambrian platform and slope facies of the Precordillera contribute additional data for a better understanding of the relationships between the eastern and the western facies assemblages, which developed in the Precordillera during the Cambrian. Therefore, they are useful for paleoenvironmental and paleogeographical interpretations of the Cambrian depositional framework

Darriwilian Conodont Biostratigraphy of the Las Chacritas Formation, Central Precordillera (San Juan Province, Argentina)

The Las Chacritas Fm in the type section in the Sierra de La Trampa, Central Precordillera (San Juan Province) was deposited in an outer carbonate ramp setting that evolved from relatively deep to shallow water. Samples from this well-exposed Middle Ordovician section yielded collections of low-diversity conodont faunas stratigraphically significant. The top of the underlying San Juan Fm and the lower and middle parts of the Las Chacritas Fm contain conodonts representative of the Lenodus variabilis Zone, and the upper part of the Las Chacritas Fm yields conodonts that correlate with the Paroistodus horridus subzone of the upper part of the Lenodus variabilis Zone. The occurrence of Dzikodus tablepointensis and Eoplacognathus pseudoplanus in the upper part of the Paroistodus horridus subzone is especially significant. The occurrence of Histiodella kristinae in the highest levels indicates that the top of the Las Chacritas Fm correlates with the Eoplacognathus suecicus Zone. Conodont biofacies are analyzed trough the entire section, supporting an outer platform or open sea conditions. Baltic and Sino-Pacific affinities are stated

Chancelloria eros Walcott, 1920 (Chancelloriidae), Diagoniella Rauff, 1894 y espículas de esponjas hexactinéllidas (Porifera, Protospongiidae) del Cámbrico Medio de San José de Gracia, Sonora, México.

Escleritos aislados de Chancelloria eros Walcott, 1920, Diagoniella sp. y asociaciones de espículas hexactinéllidas-estauractinas y hexactina-pentactinas son descritas para el Cámbrico Medio de San José de Gracia, Sonora, México. El material procede de una secuencia sedimentaria marina de plataforma exterior, constituida principalmente por lutita intercalada con caliza, en asociación con fósiles representativos de la Biozona de Albertella como lo es Peronopsis bonnerensis Resser, 1938; Oryctocephalites walcotti Reeser, 1938; Elrathina antiqua Palmer y Halley, 1979 y Ogygopsis typicalis Resser, 1939; así como braquiópodos inarticulados. Chancelloria eros Walcott, 1920 ha sido reportada anteriormente para el Estado de Sonora, México, en el Cámbrico Medio de la Formación Arrojos, así como Chancelloria sp. en el Cámbrico Temprano de la Formación Puerto Blanco, en asociación con Kiwetinokia en Cerro Rajón en la región de Caborca. Siendo el presente el primer registro para San José de Gracia, Sonora central.Fil: Cuen R, Francisco J.. Universidad de Sonora; MéxicoFil: Beresi, Matilde Sylvia. Consejo Nacional de Investigaciones Científicas y Técnicas. Científico Tecnológico Mendoza. Instituto Argentino de Nivologia, Glaciologia y Ciencias Ambientales; ArgentinaFil: Montijo, A.. Universidad de Sonora; MéxicoFil: Buitrón, B. E.. Universidad Nacional Autónoma de México; MéxicoFil: Minjares, M. de la O.. Universidad de Sonora; Méxic

Cambrian sponge spicules and Chancelloriid sclerites from the Argentine Precordillera : a Review

Spicules of sponges and sclerites of chancelloriids have been collected from in situ Cambrian sections of the La Laja Formation (San Juan Precordillera). They have also been collected from carbonate olistoliths, which were emplaced from the Cambrian units in the Early Ordovician Los Sombreros Formation (San Juan Precordillera) and Empozada Formation (Mendoza Precordillera). The Cambrian La Laja Formation sequences were deposited in a shallow carbonate platform in the eastern part of the Precordillera. The Cambrian carbonate rocks, which make up the olistoliths in the Los Sombreros and Empozada Formations, record deposition in the slope environments which developed in the western Precordillera. Cambrian Porifera and sponge-like chancelloriid assemblages are known mainly from fragments of skeletal nets, dissociated spicules and sclerites, which enable us to define two assemblages. The first assemblage of spicules was defined from the upper Lower to Middle Cambrian sequences of the La Laja Formation. This assemblage consists of a variety of stauractines and sclerites of Chancelloria WALCOTT. The family Protospongiidae is represented by triradiate prodianes, pentactines and hexactines, all belonging to Kiwetinokia WALCOTT. The second assemblage, which consists of isolated hexactines, pentactines, monaxons and skeletal nets, was defined in the Cambrian derived olistholiths of the Los Sombreros and Empozada Formations. Early hexactinellid Protospongiidae with body preservation (Diagoniella ? and Kiwetinokia) also occur. Demosponges have a very limited record in the Cambrian of the Precordillera. Anthaspidellid sponges had been reported from the La Laja Formation and now from the San Martín olistolith (Empozada Formation). The occurrences of these two assemblages of spicules and sclerites in both the Cambrian platform and slope facies of the Precordillera contribute additional data for a better understanding of the relationships between the eastern and the western facies assemblages, which developed in the Precordillera during the Cambrian. Therefore, they are useful for paleoenvironmental and paleogeographical interpretations of the Cambrian depositional framework

Cambrian sponge spicules and Chancelloriid sclerites from the Argentine Precordillera: A Review

Spicules of sponges and sclerites of chancelloriids have been collected from in situ Cambrian sections of the La Laja Formation (San Juan Precordillera). They have also been collected from carbonate olistoliths, which were emplaced from the Cambrian units in the Early Ordovician Los Sombreros Formation (San Juan Precordillera) and Empozada Formation (Mendoza Precordillera). The Cambrian La Laja Formation sequences were deposited in a shallow carbonate platform in the eastern part of the Precordillera. The Cambrian carbonate rocks, which make up the olistoliths in the Los Sombreros and Empozada Formations, record deposition in the slope environments which developed in the western Precordillera. Cambrian Porifera and sponge-like chancelloriid assemblages are known mainly from fragments of skeletal nets, dissociated spicules and sclerites, which enable us to define two assemblages. The first assemblage of spicules was defined from the upper Lower to Middle Cambrian sequences of the La Laja Formation. This assemblage consists of a variety of stauractines and sclerites of Chancelloria WALCOTT. The family Protospongiidae is represented by triradiate prodianes, pentactines and hexactines, all belonging to Kiwetinokia WALCOTT. The second assemblage, which consists of isolated hexactines, pentactines, monaxons and skeletal nets, was defined in the Cambrian derived olistholiths of the Los Sombreros and Empozada Formations. Early hexactinellid Protospongiidae with body preservation (Diagoniella ? and Kiwetinokia) also occur. Demosponges have a very limited record in the Cambrian of the Precordillera. Anthaspidellid sponges had been reported from the La Laja Formation and now from the San Martín olistolith (Empozada Formation). The occurrences of these two assemblages of spicules and sclerites in both the Cambrian platform and slope facies of the Precordillera contribute additional data for a better understanding of the relationships between the eastern and the western facies assemblages, which developed in the Precordillera during the Cambrian. Therefore, they are useful for paleoenvironmental and paleogeographical interpretations of the Cambrian depositional framework

Microfacies asociadas a las Zonas de <i>Oepikodus evae</i> y <i>O. intermedius</i> (Conodonta) en el Ordovícico de Salagasta, Mendoza, Argentina

En la localidad de Salagasta, ubicada en el extremo austral de la Sierra de La Higuera, provincia de Mendoza aflora una secuencia eopaleozoica afectada tectónicamente, que forma parte de la Provincia Geológica de Precordillera. La franja de calizas correspondiente a la plataforma ordovícica de la Formación San Juan, ingresa en la Precordillera de Mendoza desde la Sierra de Las Peñas (provincia de San Juan) y aparece en la región septentrional de la Sierra de La Higuera. Se han caracterizado las microfacies y los conodontes asociados para el miembro superior (32m), correspondiente a los tramos medio y superior de la sección carbonática. El miembro superior está caracterizado por microfacies de packstones de pellets que pasan a grainstones fosilíferos y grainstones crinoidales asociadas a estructuras sedimentarias de media a alta energía. En los 4m cuspidales de la Formación San Juan, las microfacies reflejan menor energía y están representadas por mudstones y wackestones pelletoidales. Los conodontes permitieron referir los tramos medio y superior de la sección carbonática a la Zona de Oepikodus evae y los tramos cuspidales a la Zona de Oepikodus intermedius. De acuerdo a las biozonas de conodontes determinadas, los términos superiores de la Formación San Juan en la región de Salagasta, Precordillera de Mendoza se asignan al Floiano más alto. La sección culmina con un paquete mixto calcáreo-pelítico de 7m de espesor correspondiente a la Formación Gualcamayo.Simposio I: 2º Simposio de bioestratigrafía y eventos del Paleozoico inferiorSymposium I: 2nd Symposium of biostratigraphy and Lower Paleozoic eventsSimpósio I: 2 º Simpósio de bioestratigrafia e eventos do Paleozoico InferiorFacultad de Ciencias Naturales y Muse

Microfacies asociadas a las Zonas de Oepikodus evae y O. intermedius (Conodonta) en el Ordovícico de Salagasta, Mendoza, Argentina

En la localidad de Salagasta, ubicada en el extremo austral de la Sierra de La Higuera, provincia de Mendoza aflora una secuencia eopaleozoica afectada tectónicamente, que forma parte de la Provincia Geológica de Precordillera. La franja de calizas correspondiente a la plataforma ordovícica de la Formación San Juan, ingresa en la Precordillera de Mendoza desde la Sierra de Las Peñas (provincia de San Juan) y aparece en la región septentrional de la Sierra de La Higuera. Se han caracterizado las microfacies y los conodontes asociados para el miembro superior (32m), correspondiente a los tramos medio y superior de la sección carbonática. El miembro superior está caracterizado por microfacies de packstones de pellets que pasan a grainstones fosilíferos y grainstones crinoidales asociadas a estructuras sedimentarias de media a alta energía. En los 4m cuspidales de la Formación San Juan, las microfacies reflejan menor energía y están representadas por mudstones y wackestones pelletoidales. Los conodontes permitieron referir los tramos medio y superior de la sección carbonática a la Zona de Oepikodus evae y los tramos cuspidales a la Zona de Oepikodus intermedius. De acuerdo a las biozonas de conodontes determinadas, los términos superiores de la Formación San Juan en la región de Salagasta, Precordillera de Mendoza se asignan al Floiano más alto. La sección culmina con un paquete mixto calcáreo-pelítico de 7m de espesor correspondiente a la Formación Gualcamayo.Simposio I: 2º Simposio de bioestratigrafía y eventos del Paleozoico inferiorSymposium I: 2nd Symposium of biostratigraphy and Lower Paleozoic eventsSimpósio I: 2 º Simpósio de bioestratigrafia e eventos do Paleozoico InferiorFacultad de Ciencias Naturales y Muse

Darriwilian Conodont Biostratigraphy of the Las Chacritas Formation, Central Precordillera (San Juan Province, Argentina)

The Las Chacritas Fm in the type section in the Sierra de La Trampa, Central Precordillera (San Juan Province) was deposited in an outer carbonate ramp setting that evolved from relatively deep to shallow water. Samples from this well-exposed Middle Ordovician section yielded collections of low-diversity conodont faunas stratigraphically significant. The top of the underlying San Juan Fm and the lower and middle parts of the Las Chacritas Fm contain conodonts representative of the Lenodus variabilis Zone, and the upper part of the Las Chacritas Fm yields conodonts that correlate with the Paroistodus horridus subzone of the upper part of the Lenodus variabilis Zone. The occurrence of Dzikodus tablepointensis and Eoplacognathus pseudoplanus in the upper part of the Paroistodus horridus subzone is especially significant. The occurrence of Histiodella kristinae in the highest levels indicates that the top of the Las Chacritas Fm correlates with the Eoplacognathus suecicus Zone. Conodont biofacies are analyzed trough the entire section, supporting an outer platform or open sea conditions. Baltic and Sino-Pacific affinities are stated

Ordovician gastropods from Argentina

Ordovician (Arenig to Lower Llanvirn) gastropods are summarized from the San Juan Formation, in the San Juan Precordillera of Argentina. Preservation is poor, but at least fourteen genera representing bellerophontoids, macluritoids, euomphaloids, pleurotomaroids, murchisonoids, and an onychochiloid are present. The San Juan Formation is the only known Ordovician occurrence of the superfamilies Macluritoidea and Onychochiloidea in South America.Fil: Beresi, Matilde Sylvia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; ArgentinaFil: Rorh, David M.. Sul Ross State University; Estados UnidosFil: Yochelson, Ellis L.. American Museum Of Natural History; Estados Unido