The microfossil hosted in the strata of the upper part of the San Juan Formation has been widely ... more The microfossil hosted in the strata of the upper part of the San Juan Formation has been widely studied in several sections to the northward of the Argentinian Central Precordillera. In contrast, the coeval strata at the Los Baños de Talacasto section, in the southern part of the Central Precordillera, have scarce biostratigraphic and sedimentological data. In this work, a conodont association together with single ostracod species are documented for the first time in this section. The record of the Lenodus crassus and L. pseudoplanus zones confirms the Darriwilian age for these beds and accurately correlates them with equivalent strata of the San Juan Formation studied in several sections of the Central and Eastern Precordillera. The microfacies analysis verifies the presence of Nuia síbirica Maslov, 1954, peloids, intraclasts, cyanobacteria, calcareous algae, and a possible microbialite indicating a shallow warm-water subtidal environment, in equatorial to subequatorial climate. T...
Elementos de la especie guía Lenodus variabilis (Sergeeva) fueron recuperados de muestras proveni... more Elementos de la especie guía Lenodus variabilis (Sergeeva) fueron recuperados de muestras provenientes de la Formación San Juan aforante en la sección del Cerro La Chilca, en la Precordillera Central de San Juan, Argentina. Estos depósitos de calizas corresponden a los últimos 15 metros de esta unidad los que están representados por packstone - wackestone bioclásticos, wackestone glauconíticos a grainstone bioclásticos. El hallazgo de L. variabilis permite registrar la biozona de conodontes homónima; estando también presente en la biozona sucesiva (Zona de Yangtzeplacognathus crassus), lo que permite verificar las similitudes entre el esquema de biozonas de conodontes del Darriwiliano medio de la Precordillera con el de Báltica y del centro-sur de China.Elements of the key species Lenodus variabilis (Sergeeva) have been recovered from samples of the San Juan Formation which is cropping out in Cerro La Chilca section, Central Precordillera (San Juan). These limestones correspond to t...
The Lower Paleo-zoic shows a wide distribution in the Central Precordillera, it has been extensiv... more The Lower Paleo-zoic shows a wide distribution in the Central Precordillera, it has been extensively studied, mainly in the north area of this morphostructural unit, however, to the southward the studies are scarce. The present contribution offers the first insight into the Lower Paleozoic stratigraphy on the western flank of the Sierra de Las Cruce-citas, which is located on the southern margin of the Bolson de Hualilán. In this area, the San Juan, La Chilca, Los Espejos, Talacasto and Punta Negra formations were recognized, but this study focuses on the first three units. The San Juan Formation is composed of light gray to medium gray limestone and the pulchrilamiloid Zondarella sp. is recognized as almost the only fossil component which represents the westernmost finding of this organism in the Precordillera. A late Dapingian-Darriwilian age is suggested for these levels based on their stratigraphic position and outcrop characteristics. Only the first few meters of the La Chilca Formation were surveyed. In the base of this unit was recognized a reddish-brown paraconglomerate with scattered angular to subangular chert clasts and cemented by silica and oxide-Fe, then follows a monotonous succession of siltstones and green shale. The Los Espejos Formation presents a coarsening-up and thickening-up arrangement , with shale and sandstones with bioclastic accumulation in the middle part, while in the upper part there are sinsedimentary deformation structures. These preliminary stratigraphic observations in this area provide valuable information about the distribution and composition of the Paleozoic units studied. However, detailed studies must be carried out to achieve a better understanding of its importance within the Paleozoic basins of the Precordillera. Resumen: El Paleozoico Inferior presenta una amplia distribución en el ámbito de la Precordillera Central, el mismo ha sido extensamente estudiado principalmente en el extremo norte de esta unidad morfoestructural, sin embargo, hacia el sur los estudios son escasos. En la presente contribución se presenta la primera aproximación a la estratigrafía del Paleozoico Inferior del flanco occidental de la Sierra de Las Crucecitas, la cual se ubica en el borde austral del Bolsón de Hualilán. En este sector se reconocieron las formaciones San Juan, La Chilca, Los Espejos, Talacasto y Punta Negra, pero el presente estudio se focaliza en las tres primeras unidades. La Formación San Juan está compuesta por calizas de color gris claro a gris medio y se reconoce, como casi el único componente fósil, al pulchrilamiloideo Zondarella sp., representando el hallazgo más occidental de dicho organismo en la Precordillera. Se sugiere una edad dapingiana tardía-darriwiliana para estos niveles en función de su posición estratigráfica y las características del afloramiento. De la Formación La Chilca solo se relevó los primeros metros de la unidad, reconociéndose a la base un paraconglomerado pardo rojizo con clastos de chert angulosos a subangulosos dispersos, fuertemente cementado por sílice y óxido de hierro, el mismo es seguido por una sucesión monótona de limolitas y pelitas verdes. La Formación Los Espejos presenta arreglo estrato-granocreciente, con pelitas y areniscas con acumulación bioclástica en la parte media, mientras que en la parte superior se observan estructuras de deformación sinsedimentaria. Estas observaciones preliminares sobre la estratigrafía de esta área, aportan valiosa información sobre la distribución y composición de las unidades paleozoicas estudiadas. Sin embargo, estudios de detalle deben llevarse a cabo para lograr una major comprensión de su importancia dentro de las cuencas paleozoicas de Precordillera.
Oneotodus sp., Scolopodus filosus, Teridontus nakamurai and Variabiloconus sp., as a part of an a... more Oneotodus sp., Scolopodus filosus, Teridontus nakamurai and Variabiloconus sp., as a part of an association that defines a pre-Paltodus deltifer Zone. The material most likely represents the Cordylodus angulatus and/or the lower part of the Rossodus manitouensis Zone. These microfossils support the dating of the Devendeus Formation as Tremadocian (Early Ordovician).
Conodonts recovered from the Devendeus Formation at the Angosto de La Quesera locality (Cordiller... more Conodonts recovered from the Devendeus Formation at the Angosto de La Quesera locality (Cordillera Oriental of Salta) in northwestern Argentina include Nogamiconus sp., Problematoconites perforatus, Drepanoistodus sp., Oneotodus sp., Scolopodus filosus, Teridontus nakamurai and Variabiloconus sp., as a part of an association that defines a pre-Paltodus deltifer Zone. The material most likely represents the Cordylodus angulatus and/or the lower part of the Rossodus manitouensis Zone. These microfossils support the dating of the Devendeus Formation as Tremadocian (Early Ordovician).
The Middle-Upper Ordovician Ponón Trehué Formation cropping out in the San Rafael Block (Argentin... more The Middle-Upper Ordovician Ponón Trehué Formation cropping out in the San Rafael Block (Argentina) provided a large collection of conodonts which have been published years ago. The species Eoplacognathus robustus and Eoplacognathus lindstroemi recovered from these strata have been revised and restudied. In this contribution we describe M and S elements that were assigned previously to Baltoniodus prevariabilis and Baltoniodus variabilis as belonging to the E. robustus and E. lindstroemi apparatuses. The morphological characters of the P, S and M elements as part of these late Eoplacognathus apparatus were analyzed and support the proposal of a new reconstruction of it. We have compared this apparatus with the Baltoniodus apparatus and suggest the inclusion of the Eoplacognathus genus into the Balognathidae family. The new architecture of the Eoplacognathus apparatus is comparable to the genus Lenodus. This analysis improves the knowledge about this index conodont group allowing a n...
FLOIAN CONODONTS FROM THE SAN JUAN FORMATION IN THE TALACASTO CREEK, SAN JUAN PRECORDILLERA: In t... more FLOIAN CONODONTS FROM THE SAN JUAN FORMATION IN THE TALACASTO CREEK, SAN JUAN PRECORDILLERA: In this contribution Floian conodonts from the San Juan Formation are reported for the first time from the classical Talacasto creek. The Oepikodus evae and Oepikodus intermedius zones are recorded which indicate upper Floian. The conodont association includes Bergstroemognathus extensus, Cornuodus longibasis, Drepanodus robustus, Drepanodus arcuatus, Drepanoistodus forceps, Erraticodon patu, Juanognathus variabilis, Jumudontus gananda, Oepikodus evae, Oepikodus intermedius, Oistodus striolatus, Oistodus lanceolatus, Paroistodus parallelus, Periodon flabellum, Protopanderodus leonardii, Protopanderodus rectus, Protopanderodus robustus, Reutterodus andinus, Rossodus barnesi, Scolopodus krummi, Trapezognathus diprion, Tropodus australis, Protoprioniodus sp. and Triangulodus sp.
In the classical section of the Don Braulio Creek at the Villicum Range, Eastern Precordillera of... more In the classical section of the Don Braulio Creek at the Villicum Range, Eastern Precordillera of San Juan Province, crops out the siliciclastic Don Braulio Formation of Hirnantian age. Fragments of bryozoan colonies, few poorly preserved sponge spicules and a crinoidal plate, were recovered from these shelf sediments. The bryozoan colonies remains are characterized by its erect growth habit, its small diameter, and for showing clear longitudinal striations. These fragments have a poor preservation, but they have been compared with the genus Nematopora belonging to the Arthrostylidae family (Rhobdomesina suborder, Cryptostomata order), that had numerous representatives during the Ordovician. Very scarce and highly fragmented sponge spicules are classified as hexactins. These microfossils have been recovered in the post-glacial deposits from the Don Braulio section at the Villicum range.
Se reconocen las zonas de Oepikodus evae y de Oepikodus intermedius indicativas del Floiano super... more Se reconocen las zonas de Oepikodus evae y de Oepikodus intermedius indicativas del Floiano superior. Las asociaciones de conodontes que acompañan a las especies guías están compuestas por:
THE LOWER PALEOZOIC IN THE EASTERN FLANK OF THE SIERRA DE PEDERNAL, CIENAGUITA, EASTERN PRE- CORD... more THE LOWER PALEOZOIC IN THE EASTERN FLANK OF THE SIERRA DE PEDERNAL, CIENAGUITA, EASTERN PRE- CORDILLERA. In the eastern flank of the Pedernal hill the Lower Paleozoic stratigraphy is complex and affected by an intense deformation. This paper describes a new section where relicts of Los Azules and Don Braulio formations are recognized for the first time; these units are overlapping the San Juan Formation and above the La Rinconada For - mation are recorded. This finding allows extending the paleographic distribution of darriwilian and hirnantian basins southward of the San Juan River at least until this region of the Eastern Precordillera. Palabras clave: Paleozoico. Estratigrafia. Cienaguita. Precordillera Oriental
primera mención para Argentina y Sudamérica. Vinculada a los estratos portadores de la icnofauna ... more primera mención para Argentina y Sudamérica. Vinculada a los estratos portadores de la icnofauna se rescató una asociación de conodontes compuesta por especies de diferentes edades del Ordovícico, de éstas la especie Erismodus cf. quadridactylus se considera la única autóctona. La edad del afloramiento se define como Ordovícico Medio-Superior (Darriwiliano tardío-Sandbiano temprano) indicada por E. cf. quadridactylus como así también por la icnoespecie hallada.
Elementos de la especie guía Lenodus variabilis (Sergeeva) fueron recuperados de muestras proveni... more Elementos de la especie guía Lenodus variabilis (Sergeeva) fueron recuperados de muestras provenientes de la Formación San Juan aflorante en la sección del Cerro La Chilca, en la Precordillera Central de San Juan, Argentina. Estos depósitos de calizas corresponden a los últimos15 metros de esta unidad los que están representados por packstone – wackestone bioclásticos, wackestone glauconíticos a grainstone bioclásticos. El hallazgo de L. variabilis permite registrar la biozona de conodontes homónima; estando también presente en la biozona sucesiva (Zona de Yangtzeplacognathus crassus), lo que permite verificar las similitudes entre el esquema de biozonas de conodontes del Darriwiliano medio de la Precordillera con el de Báltica y del centro-sur de China.
The Middle Ordovician carbonate Las Aguaditas Formation was sampled for conodonts at the Las Chac... more The Middle Ordovician carbonate Las Aguaditas Formation was sampled for conodonts at the Las Chacritas Creek, Sierra de La Trampa, Central Precordillera. The middle Darriwilian index conodonts Eoplacognathus pseudoplanus Viira and Eoplacognathus suecicus ...
Recent studies on classical Silurian sections of the Central Precordillera provided conodont faun... more Recent studies on classical Silurian sections of the Central Precordillera provided conodont faunas which allow the proposal of a new biostratigraphical chart for the Silurian deposits of the Precordillera. The Cerro del Fuerte, Loma de Los Piojos, Cerro La Chilca and ...
ABSTRACT Three different species of the Ordovician genus Erraticodon Dzik are described and illus... more ABSTRACT Three different species of the Ordovician genus Erraticodon Dzik are described and illustrated. Erraticodon patu Cooper is reported from the Lower–Midde Ordovician strata of the Acoite and Alto del Cóndor formations. E. cf. Erraticodon balticus and Erraticodon hexianensis from Middle Ordovician carbonate deposits of the San Juan Formation are analyzed and compared to specimens of these species from Australia, China, Newfoundland, and Baltica. E. patu and E. hexianensis are recorded for first time in the San Juan Formation of Precordillera. The elements of E. cf. E. balticus resemble closely E. balticus Dzik but lack the important denticle on the posterior process of the S elements. An evaluation of the stratigraphic occurrences of these species relative to those of key Lower and Middle Ordovician conodont species such as Trapezognathus diprion Lindström, Oepikodus intermedius Serpagli, Baltoniodus triangularis (Lindström), Baltoniodus navis Lindström, Yangtzeplacognathus crassus (Chen and Zhang) and Eoplacognathus pseudoplanus (Viira) indicates they value for biostratigraphic correlation.
The microfossil hosted in the strata of the upper part of the San Juan Formation has been widely ... more The microfossil hosted in the strata of the upper part of the San Juan Formation has been widely studied in several sections to the northward of the Argentinian Central Precordillera. In contrast, the coeval strata at the Los Baños de Talacasto section, in the southern part of the Central Precordillera, have scarce biostratigraphic and sedimentological data. In this work, a conodont association together with single ostracod species are documented for the first time in this section. The record of the Lenodus crassus and L. pseudoplanus zones confirms the Darriwilian age for these beds and accurately correlates them with equivalent strata of the San Juan Formation studied in several sections of the Central and Eastern Precordillera. The microfacies analysis verifies the presence of Nuia síbirica Maslov, 1954, peloids, intraclasts, cyanobacteria, calcareous algae, and a possible microbialite indicating a shallow warm-water subtidal environment, in equatorial to subequatorial climate. T...
Elementos de la especie guía Lenodus variabilis (Sergeeva) fueron recuperados de muestras proveni... more Elementos de la especie guía Lenodus variabilis (Sergeeva) fueron recuperados de muestras provenientes de la Formación San Juan aforante en la sección del Cerro La Chilca, en la Precordillera Central de San Juan, Argentina. Estos depósitos de calizas corresponden a los últimos 15 metros de esta unidad los que están representados por packstone - wackestone bioclásticos, wackestone glauconíticos a grainstone bioclásticos. El hallazgo de L. variabilis permite registrar la biozona de conodontes homónima; estando también presente en la biozona sucesiva (Zona de Yangtzeplacognathus crassus), lo que permite verificar las similitudes entre el esquema de biozonas de conodontes del Darriwiliano medio de la Precordillera con el de Báltica y del centro-sur de China.Elements of the key species Lenodus variabilis (Sergeeva) have been recovered from samples of the San Juan Formation which is cropping out in Cerro La Chilca section, Central Precordillera (San Juan). These limestones correspond to t...
The Lower Paleo-zoic shows a wide distribution in the Central Precordillera, it has been extensiv... more The Lower Paleo-zoic shows a wide distribution in the Central Precordillera, it has been extensively studied, mainly in the north area of this morphostructural unit, however, to the southward the studies are scarce. The present contribution offers the first insight into the Lower Paleozoic stratigraphy on the western flank of the Sierra de Las Cruce-citas, which is located on the southern margin of the Bolson de Hualilán. In this area, the San Juan, La Chilca, Los Espejos, Talacasto and Punta Negra formations were recognized, but this study focuses on the first three units. The San Juan Formation is composed of light gray to medium gray limestone and the pulchrilamiloid Zondarella sp. is recognized as almost the only fossil component which represents the westernmost finding of this organism in the Precordillera. A late Dapingian-Darriwilian age is suggested for these levels based on their stratigraphic position and outcrop characteristics. Only the first few meters of the La Chilca Formation were surveyed. In the base of this unit was recognized a reddish-brown paraconglomerate with scattered angular to subangular chert clasts and cemented by silica and oxide-Fe, then follows a monotonous succession of siltstones and green shale. The Los Espejos Formation presents a coarsening-up and thickening-up arrangement , with shale and sandstones with bioclastic accumulation in the middle part, while in the upper part there are sinsedimentary deformation structures. These preliminary stratigraphic observations in this area provide valuable information about the distribution and composition of the Paleozoic units studied. However, detailed studies must be carried out to achieve a better understanding of its importance within the Paleozoic basins of the Precordillera. Resumen: El Paleozoico Inferior presenta una amplia distribución en el ámbito de la Precordillera Central, el mismo ha sido extensamente estudiado principalmente en el extremo norte de esta unidad morfoestructural, sin embargo, hacia el sur los estudios son escasos. En la presente contribución se presenta la primera aproximación a la estratigrafía del Paleozoico Inferior del flanco occidental de la Sierra de Las Crucecitas, la cual se ubica en el borde austral del Bolsón de Hualilán. En este sector se reconocieron las formaciones San Juan, La Chilca, Los Espejos, Talacasto y Punta Negra, pero el presente estudio se focaliza en las tres primeras unidades. La Formación San Juan está compuesta por calizas de color gris claro a gris medio y se reconoce, como casi el único componente fósil, al pulchrilamiloideo Zondarella sp., representando el hallazgo más occidental de dicho organismo en la Precordillera. Se sugiere una edad dapingiana tardía-darriwiliana para estos niveles en función de su posición estratigráfica y las características del afloramiento. De la Formación La Chilca solo se relevó los primeros metros de la unidad, reconociéndose a la base un paraconglomerado pardo rojizo con clastos de chert angulosos a subangulosos dispersos, fuertemente cementado por sílice y óxido de hierro, el mismo es seguido por una sucesión monótona de limolitas y pelitas verdes. La Formación Los Espejos presenta arreglo estrato-granocreciente, con pelitas y areniscas con acumulación bioclástica en la parte media, mientras que en la parte superior se observan estructuras de deformación sinsedimentaria. Estas observaciones preliminares sobre la estratigrafía de esta área, aportan valiosa información sobre la distribución y composición de las unidades paleozoicas estudiadas. Sin embargo, estudios de detalle deben llevarse a cabo para lograr una major comprensión de su importancia dentro de las cuencas paleozoicas de Precordillera.
Oneotodus sp., Scolopodus filosus, Teridontus nakamurai and Variabiloconus sp., as a part of an a... more Oneotodus sp., Scolopodus filosus, Teridontus nakamurai and Variabiloconus sp., as a part of an association that defines a pre-Paltodus deltifer Zone. The material most likely represents the Cordylodus angulatus and/or the lower part of the Rossodus manitouensis Zone. These microfossils support the dating of the Devendeus Formation as Tremadocian (Early Ordovician).
Conodonts recovered from the Devendeus Formation at the Angosto de La Quesera locality (Cordiller... more Conodonts recovered from the Devendeus Formation at the Angosto de La Quesera locality (Cordillera Oriental of Salta) in northwestern Argentina include Nogamiconus sp., Problematoconites perforatus, Drepanoistodus sp., Oneotodus sp., Scolopodus filosus, Teridontus nakamurai and Variabiloconus sp., as a part of an association that defines a pre-Paltodus deltifer Zone. The material most likely represents the Cordylodus angulatus and/or the lower part of the Rossodus manitouensis Zone. These microfossils support the dating of the Devendeus Formation as Tremadocian (Early Ordovician).
The Middle-Upper Ordovician Ponón Trehué Formation cropping out in the San Rafael Block (Argentin... more The Middle-Upper Ordovician Ponón Trehué Formation cropping out in the San Rafael Block (Argentina) provided a large collection of conodonts which have been published years ago. The species Eoplacognathus robustus and Eoplacognathus lindstroemi recovered from these strata have been revised and restudied. In this contribution we describe M and S elements that were assigned previously to Baltoniodus prevariabilis and Baltoniodus variabilis as belonging to the E. robustus and E. lindstroemi apparatuses. The morphological characters of the P, S and M elements as part of these late Eoplacognathus apparatus were analyzed and support the proposal of a new reconstruction of it. We have compared this apparatus with the Baltoniodus apparatus and suggest the inclusion of the Eoplacognathus genus into the Balognathidae family. The new architecture of the Eoplacognathus apparatus is comparable to the genus Lenodus. This analysis improves the knowledge about this index conodont group allowing a n...
FLOIAN CONODONTS FROM THE SAN JUAN FORMATION IN THE TALACASTO CREEK, SAN JUAN PRECORDILLERA: In t... more FLOIAN CONODONTS FROM THE SAN JUAN FORMATION IN THE TALACASTO CREEK, SAN JUAN PRECORDILLERA: In this contribution Floian conodonts from the San Juan Formation are reported for the first time from the classical Talacasto creek. The Oepikodus evae and Oepikodus intermedius zones are recorded which indicate upper Floian. The conodont association includes Bergstroemognathus extensus, Cornuodus longibasis, Drepanodus robustus, Drepanodus arcuatus, Drepanoistodus forceps, Erraticodon patu, Juanognathus variabilis, Jumudontus gananda, Oepikodus evae, Oepikodus intermedius, Oistodus striolatus, Oistodus lanceolatus, Paroistodus parallelus, Periodon flabellum, Protopanderodus leonardii, Protopanderodus rectus, Protopanderodus robustus, Reutterodus andinus, Rossodus barnesi, Scolopodus krummi, Trapezognathus diprion, Tropodus australis, Protoprioniodus sp. and Triangulodus sp.
In the classical section of the Don Braulio Creek at the Villicum Range, Eastern Precordillera of... more In the classical section of the Don Braulio Creek at the Villicum Range, Eastern Precordillera of San Juan Province, crops out the siliciclastic Don Braulio Formation of Hirnantian age. Fragments of bryozoan colonies, few poorly preserved sponge spicules and a crinoidal plate, were recovered from these shelf sediments. The bryozoan colonies remains are characterized by its erect growth habit, its small diameter, and for showing clear longitudinal striations. These fragments have a poor preservation, but they have been compared with the genus Nematopora belonging to the Arthrostylidae family (Rhobdomesina suborder, Cryptostomata order), that had numerous representatives during the Ordovician. Very scarce and highly fragmented sponge spicules are classified as hexactins. These microfossils have been recovered in the post-glacial deposits from the Don Braulio section at the Villicum range.
Se reconocen las zonas de Oepikodus evae y de Oepikodus intermedius indicativas del Floiano super... more Se reconocen las zonas de Oepikodus evae y de Oepikodus intermedius indicativas del Floiano superior. Las asociaciones de conodontes que acompañan a las especies guías están compuestas por:
THE LOWER PALEOZOIC IN THE EASTERN FLANK OF THE SIERRA DE PEDERNAL, CIENAGUITA, EASTERN PRE- CORD... more THE LOWER PALEOZOIC IN THE EASTERN FLANK OF THE SIERRA DE PEDERNAL, CIENAGUITA, EASTERN PRE- CORDILLERA. In the eastern flank of the Pedernal hill the Lower Paleozoic stratigraphy is complex and affected by an intense deformation. This paper describes a new section where relicts of Los Azules and Don Braulio formations are recognized for the first time; these units are overlapping the San Juan Formation and above the La Rinconada For - mation are recorded. This finding allows extending the paleographic distribution of darriwilian and hirnantian basins southward of the San Juan River at least until this region of the Eastern Precordillera. Palabras clave: Paleozoico. Estratigrafia. Cienaguita. Precordillera Oriental
primera mención para Argentina y Sudamérica. Vinculada a los estratos portadores de la icnofauna ... more primera mención para Argentina y Sudamérica. Vinculada a los estratos portadores de la icnofauna se rescató una asociación de conodontes compuesta por especies de diferentes edades del Ordovícico, de éstas la especie Erismodus cf. quadridactylus se considera la única autóctona. La edad del afloramiento se define como Ordovícico Medio-Superior (Darriwiliano tardío-Sandbiano temprano) indicada por E. cf. quadridactylus como así también por la icnoespecie hallada.
Elementos de la especie guía Lenodus variabilis (Sergeeva) fueron recuperados de muestras proveni... more Elementos de la especie guía Lenodus variabilis (Sergeeva) fueron recuperados de muestras provenientes de la Formación San Juan aflorante en la sección del Cerro La Chilca, en la Precordillera Central de San Juan, Argentina. Estos depósitos de calizas corresponden a los últimos15 metros de esta unidad los que están representados por packstone – wackestone bioclásticos, wackestone glauconíticos a grainstone bioclásticos. El hallazgo de L. variabilis permite registrar la biozona de conodontes homónima; estando también presente en la biozona sucesiva (Zona de Yangtzeplacognathus crassus), lo que permite verificar las similitudes entre el esquema de biozonas de conodontes del Darriwiliano medio de la Precordillera con el de Báltica y del centro-sur de China.
The Middle Ordovician carbonate Las Aguaditas Formation was sampled for conodonts at the Las Chac... more The Middle Ordovician carbonate Las Aguaditas Formation was sampled for conodonts at the Las Chacritas Creek, Sierra de La Trampa, Central Precordillera. The middle Darriwilian index conodonts Eoplacognathus pseudoplanus Viira and Eoplacognathus suecicus ...
Recent studies on classical Silurian sections of the Central Precordillera provided conodont faun... more Recent studies on classical Silurian sections of the Central Precordillera provided conodont faunas which allow the proposal of a new biostratigraphical chart for the Silurian deposits of the Precordillera. The Cerro del Fuerte, Loma de Los Piojos, Cerro La Chilca and ...
ABSTRACT Three different species of the Ordovician genus Erraticodon Dzik are described and illus... more ABSTRACT Three different species of the Ordovician genus Erraticodon Dzik are described and illustrated. Erraticodon patu Cooper is reported from the Lower–Midde Ordovician strata of the Acoite and Alto del Cóndor formations. E. cf. Erraticodon balticus and Erraticodon hexianensis from Middle Ordovician carbonate deposits of the San Juan Formation are analyzed and compared to specimens of these species from Australia, China, Newfoundland, and Baltica. E. patu and E. hexianensis are recorded for first time in the San Juan Formation of Precordillera. The elements of E. cf. E. balticus resemble closely E. balticus Dzik but lack the important denticle on the posterior process of the S elements. An evaluation of the stratigraphic occurrences of these species relative to those of key Lower and Middle Ordovician conodont species such as Trapezognathus diprion Lindström, Oepikodus intermedius Serpagli, Baltoniodus triangularis (Lindström), Baltoniodus navis Lindström, Yangtzeplacognathus crassus (Chen and Zhang) and Eoplacognathus pseudoplanus (Viira) indicates they value for biostratigraphic correlation.
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