Papers by Pablo J . Pazos
Introduction to journal of South American Earth sciences special issue on “Ichnology through the Phanerozoic: A Latin America perspective”
Journal of South American Earth Sciences, Dec 1, 2021
Geological Society, London, Special Publications, Feb 9, 2022
The ichnogenus Psammichnites herein restricted to Psammichnites gigas is based on comparison of m... more The ichnogenus Psammichnites herein restricted to Psammichnites gigas is based on comparison of morphology, feeding behaviour, contrast between the burrows and the host rock and possible producers. The record of siphonal activity as a "snorkel device" is discussed. The diagnosis of the ichnogenus Olivellites now is amended and includes all the records of Psammichnites in the post-Cambrian. Olivellites is now documented in successions other than the classical tidal flat deposits facies of the Carboniferous of the USA. We propose
Dictyodora-Nereites dominated ichnofauna in the Silurian−Devonian turbidite-like deposits of central-western Gondwana (San Rafael Block, Argentina): New stratigraphic and bathymetric constraints
Journal of South American Earth Sciences, Jun 1, 2021
Abstract The Rio Seco de los Castanos Formation (San Rafael Block) holds one of the few middle Pa... more Abstract The Rio Seco de los Castanos Formation (San Rafael Block) holds one of the few middle Palaeozoic (Silurian−Devonian) records worldwide of a Nereites-Dictyodora dominated ichnofauna with sedimentological features such as oscillatory and combined-flow deposits. This record is associated with microbial mats in fine-grained intervals between turbidite-like deposits documented above the storm wave base. In this work, a detailed sedimentological study permitted to divide the unit into two informal sections separated by an erosional unconformity attributed to a sea level fall. Prograding turbidite-like sand-grained deposits document gravitational turbulent flows. The tectonostratigraphic framework allowed to disregard a submarine fan, whereas the unconformity does not support an autocyclic deltaic evolution. Palaeocurrents and palaeoslope indicators to the SW suggest a high source area to the NE, that contrasts with the well-established E-W trend of most of the units of similar age in the Cuyania terrane. Deposition was probably deflected by subaqueous highs with the development of mini-basins most likely structurally controlled. The ichnological analysis allowed to recognise ichnotaxa and intergradation cases between ichnospecies previously unknown for the unit, adding to the most diverse record of Dictyodora and Nereites in central-western Gondwana. Chondrites intricatus, Chondrites targionii, Chondrites?, Dictyodora zimmermanni, and specimens resembling Dictyodora liebeana are recorded for the first time. Nereites missouriensis is documented in intergradation with Nereites jacksoni, whereas Dictyodora scotica is recognised in intergradation with Dictyodora atuelica and Dictyodora tenuis. A decrease in ichnodiversity throughout the section could be related to variation in environmental parameters between the lower and upper sections. The ichnofacies assignment is discussed in terms of ethological categories and ichnodiversity. Some of the defined ichnoassemblages are assignable to a non-standard record of the Nereites Ichnofacies, and one in particular to the Nereites Ichnosubfacies, while another shows some characteristics coincident with the Zoophycos Ichnofacies. A transitional case between ichnofacies for the ichnological content of the unit as a whole, as previously reported in other units, cannot be disregarded.
The Intramalmic-Intersenonian Interval in the NE Border of the Neuquén Basin. Remaining Prospectivity Assessed Through Paleoenvironmental Models and Sequential Analysis
Morphological variations in dinosaur tridactyl tracks from the Candeleros Formation (Upper Cretaceous) of northwestern Patagonia, Argentina
Journal of South American Earth Sciences, Jun 1, 2021
Abstract Several dinosaur tridactyl tracks showing inter- and intra-trackways morphological varia... more Abstract Several dinosaur tridactyl tracks showing inter- and intra-trackways morphological variations from the Cenomanian Candeleros Formation of the Neuquen Basin, Argentina, have been documented. Footprints occur on three different stratigraphic levels and are impressed on medium-grained sandstone of fluvial origin. Level 1 includes deep tridactyl tracks with metatarsal impressions (average length of 31 cm) preserved as true tracks and undertracks that could have been generated due to simply sinking of the pes into a soft substrate and also probably by a continuous walk in a squatting position. Level 2 shows the largest tridactyl tracks (average length of 58 cm) recognized in this work, situated a few meters close to an already studied sauropod trackway. The different preservation between these bipedal and quadrupedal tracks could be explained due to different substrate properties and dissimilarities of the pedal shape between trackmakers. Level 3 comprises small to large tridactyl tracks (length from 6 to 34 cm) including intra-trackway morphological variation, that is interpreted as a result of changes in the substrate properties, mainly moisture content, along the tracking surface. Taking into account that the footprints studied here are poorly preserved, they were not assigned to any particular ichnotaxon. The large tridactyl tracks have been attributed to carcharodontosaurid theropod trackmakers while medium and small tracks to undetermined bipedal dinosaur. One pair of these large theropod tracks was closely documented on the same tracking surface of the aforementioned studied sauropod trackway, attributed to rebbachisaurids. This suggests that both carcharodontosaurid and rebbachisaurid trackmakers coexisted in the same habitats as the osteological record noted. This tracksite represents an example of the morphological variability of dinosaur tridactyl tracks controlled mainly by the substrate properties, and how an approach aimed at understanding footprint formation and preservation is necessary before beginning ichnotaxonomical studies, among others.
<i>Protovirgularia dichotoma—Protovirgularia rugosa</i>: An Example of a Compound Trace Fossil from the Lower Cretaceous (Agrio Formation) of the Neuquén Basin, Argentina
Ichnos, Feb 26, 2010
This study focuses on the description of a compound trace fossil from the Cretaceous of the Neuqu... more This study focuses on the description of a compound trace fossil from the Cretaceous of the Neuquén Basin, Argentina. This structure comprises two discrete ichnotaxa: Protovirgularia cf. dichotoma M’Coy, 1850, and Protovirgularia cf. rugosa (Miller and Dyer, 1878). Open nomenclature is chosen due to some differences from the ichnospecies diagnoses. The compound trace as a whole is the product of
Geological Society, London, Special Publications, Jul 28, 2022
Several elongated and other crescent-shaped impressions interpreted as dinosaur tracks and preser... more Several elongated and other crescent-shaped impressions interpreted as dinosaur tracks and preserved on Lower Cretaceous tidal flat deposits from the Agrio Formation (northern Patagonia, Argentina) are studied in detail. These tracks were documented on a palaeosurface showing palaeotopographic differences over a short distance, related to the lateral migration of a tidal channel. A genetic order between biostabilization and bioturbation
AAPG Bulletin, Aug 1, 2020
This contribution aims to analyse depositional and post-depositional processes from two volcanic ... more This contribution aims to analyse depositional and post-depositional processes from two volcanic caves (Baño Nuevo 1 and Cueva de la Vieja) from west-central Patagonia, in order to evaluate if natural and anthropogenic processes recorded therein are representative of basin-scale processes. For this purpose, geomorphological, sedimentological, micromorphological, petrographic, magnetic, paleontological and archaeological data are integrated. Results allow correlating the Baño Nuevo 1 and Cueva de la Vieja sequences, comprising a record of ca. 19000 years. In the first place, the distinction between endogenous and exogenous detritus input, mainly recorded by the mineralogy and lithotypes, provided environmental data related to landscape stability (i.e., vegetation cover). The latter, in turn, could be interpreted as part of a complex feedback associated with major climatic changes.
Ichnological research in Lower Cretaceous marginal-marine facies from Patagonia: outcrop studies, SEM examinations and paleontological/sedimentological integration
Neues Jahrbuch für Geologie und Paläontologie, Aug 1, 2015
In-depth ichnological studies of Lower Cretaceous, marginal-marine facies from the Agrio Formatio... more In-depth ichnological studies of Lower Cretaceous, marginal-marine facies from the Agrio Formation (Patagonia, Argentina) have been carried out during the past few years. Several ichnofossils were identified and described for the first time in this unit, including a new ichnospecies (Hillichnus agrioensis) produced by tellinid bivalves, xiphosurid trackways (the first record from the Early Cretaceous worldwide) and dinosaur tracks (one of the few examples from Early Cretaceous carbonates in Gondwana). The sedimentological information showed the presence of marginal-marine intervals previously interpreted as open marine. The outcrop studies resulted in the finding of indirect evidence of microbial mats, while SEM examinations resulted in the direct evidence of their presence in certain levels; this has taphonomical implications. Both ichnological and sedimentological results allowed to challenge previous facies model belts that suggested permanent submerged littoral facies for this part of the basin during the Early Cretaceous. The inferred paleoenvironment for the top of the unit is shallower and more tidally-influenced than previously thought.Fil: Fernández, Diana Elizabeth. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos; ArgentinaFil: Pazos, Pablo Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos; Argentin
Sedimentological analysis of outer ramp facies: The Agrio Formation (Lower Cretaceous) in the cen... more Sedimentological analysis of outer ramp facies: The Agrio Formation (Lower Cretaceous) in the central sector of the Neuquén Basin, Argentina. Microfacies of distal marine deposits of the Lower Cretaceous Agrio Formation-Pilmatué and Agua de la Mula members-in the Neuquén basin has been analyzed taken into account field data, whole-rock phase-minerals and clay mineralogy with X-ray diffraction, organic components and optical and electron microscopy. Depositional and diagenetic fabrics are compared for the lowermost part of both members. Two facies associations were distinguished that correspond to two depositional settings: distal outer ramp (FA-1); and, proximal outer ramp (FA-2). FA-1 is composed of sediments mainly deposited by suspension settling with calcareous microfossils partially preserved as fecal pellets and organo-minerallic aggregates related to high bioproductivity in the water column. Conversely, FA-2 is dominated by extrabasinal components with illite-rich clay-to silt-sized particle aggregates. Storm-influenced processes have a main role in sediment transportation and accumulation as well as controlling oxygenation pulses of the bottom waters. In addition, burial diagenesis was evaluated taking into account thermal maturity of organics together with diagenetic textures such as growth of authigenic minerals and mechanical and chemical compaction features. Due to clay mineral assemblages are mainly detrital in origin the possible effects of burial diagenesis on them cannot be directly evaluated.
Revista de la Asociación Geológica Argentina, Oct 1, 2009
En este trabajo se realiza una síntesis icnológica de las unidades marinas de la cuenca Neuquina ... more En este trabajo se realiza una síntesis icnológica de las unidades marinas de la cuenca Neuquina teniendo en cuenta el marco estratigráfico de los hallazgos, se presentan nuevos datos y se mencionan aquellos aspectos aún no abordados. Los registros más antiguos han sido documentados en el Jurásico y contienen icnotaxones (Lapispira) que han sido descriptos por primera vez para Sudamérica en facies de plataforma. Otros constituyen un muy buen ejemplo de trazas bien preservadas en depósitos deltaicos jurásicos de la Formación Lajas, con influencia mareal. Allí, el registro incluye Asterosoma, Asteriacites, Dactyloidites, Diplocraterion, Gyrochorte, Palaeophycus, Polykladichnus, Schaubcilindrichnus, Siphonichnus, Thalassinoides, Teichichnus y trazas poco frecuentes en ambientes marinos someros como Helminthorhaphe y rizolitos, entre otras, indicativas de un complejo engranaje de facies. Los carbonatos jurásicos de la Formación La Manga contienen tempestitas con Dactyloidites, Gyrochorte, Jamerosonichnites y Thalassinoides, en Bardas Blancas. El registro icnológico del Cretácico Inferior se halla documentado en las Formaciones Mulichinco y Agrio. En la primera los icnofósiles aparecen en la zona de Vega de Escalone y comprenden Asteriacites, Lockeia, Ophiomorpha, Gyrochorte y posiblemente Bergaueria. En la Formación Agrio, tanto en Bajada del Agrio (localidad tipo) como en otras localidades dispersas en la cuenca aparecen icnofósiles tales como Gyrochorte, Ophiomorpha, Thalassinoides y Teichichnus. Nuevo material proveniente de ambas unidades incluye scratchs subácueos o de arrastre de vertebrados (Characichnos?) provenientes de las localidades de Vega de Escalone y Puerta Curaco. Las trazas de locomoción de artrópodos incluyen formas con apéndices diferenciados (Diplichnites?) e indiferenciados. En la Formación Agrio se reconocieron huellas tridáctilas de terópodos en el anticlinal cerro Rayoso, que confirman exposición subaérea en una zona hasta el presente interpretada como cercana al depocentro de la cuenca. En Mina La Continental se han documentado trazas complejas atribuibles a bivalvos tellínidos asignables a Hillichnus. En la mencionada localidad, aparecen huellas de terópodos. Éstas, como las de tellínidos anteceden el registro de fósiles corpóreos, que marcan condiciones de somerización extrema hasta exposición subaérea, lo que muestra claramente el valor de los estudios icnológicos en las interpretaciones paleoambientales, particularmente en sucesiones donde otros tipos de fósiles se hallan ausentes. Quedan numerosos intervalos marinos y unidades que aún no han sido estudiados, pero sin duda uno de los más interesantes se halla en la Formación Molles de naturaleza turbidítica o hiperpícnica, de la que no se conocen datos icnológicos. Del mismo modo son casi inexistentes los estudios de bioerosión y registros de trazas producidas por la meiofauna. Por todo ello, el conocimiento icnológico de los intervalos marinos de la cuenca Neuquina está en su infancia, si se lo compara con estudios paleontológicos de tipo bioestratigráfico, sedimentológicos o de rutina en la industria del petróleo tanto en afloramiento como en coronas.
Dr. Renato Rodolfo Andreis: (1935-2009)
Revista de la Asociación Geológica Argentina, Jan 10, 2009
Ciclos mareales dolimitizados en el Miembro Agua de la Mula de la Formación Agrio (Cretácico Inferior), Cuenca Neuquina, Argentina
Latin American journal of sedimentology and basin analysis, 2009
Abstract: The Agrio Formation (Valanginian to early Barremian) is a siliciclastic and carbonate u... more Abstract: The Agrio Formation (Valanginian to early Barremian) is a siliciclastic and carbonate unit of the Neuquén Basin in west central Argentina. A conspicuous 20 m thick dolomitized section near the top of the upper Agua de la Mula Member of the Agrio Formation was identified ...
Sintesis icnológica de unidades mesozoicas marinas de la Cuenca Neuquina, nuevos datos y perspectivas
Revista de la Asociación Geológica Argentina, Oct 1, 2009
ABSTRACT Ichnological synthesis of the marine units of the Neuquén Basin, new data and future per... more ABSTRACT Ichnological synthesis of the marine units of the Neuquén Basin, new data and future perspectives. In this paper the ichnology of the marine intervals of the Neuquén Basin is reviewed, taking into account an stratigraphic framework and discussing previous works on ichnology that contain some ichnogenera (Lapispira) that are firstly documented in South America in Jurassic of the Río Atuel area, and other ichnogenera that constitute well preserved records in the Jurassic tidal influenced deltas of the Lajas Formation. The trace fossil record includes Asterosoma, Asteriacites, Dactyloidites, Diplocraterion, Gyrochorte, Palaeophycus, Polykladichnus, Schaubcilindrichnus, Siphonichnus, Thalassinoides, Teichichnus and rare traces in shallow marine deposits like Helminthorhaphe and root traces indicative of a very complex facies scheme. A special mention deserves the traces from the carbonates of the La Manga Formation at Bardas Blancas, that contain ichnogenera like Dactyloidites, Gyrochorte, Jamerosonichnites and Thalassinoides recorded in tempestites. The Lower Cretaceous record documented in the Mulichinco and Agrio Formation is composed of Asteriacites, Gyrochorte, Lockeia, Ophiomorpha, and possibly Bergaueria, documented in the Mulichinco Formation at Vega de Escalone locality. Other traces described in the Agrio Formation are Gyrochorte, Ophiomorpha, Thalassinoides, Teichichnus among others of dubious assignation recorded at Bajada del Agrio and other areas of the basin. New material coming from both units includes subaqueous vertebrate scratchs (Characichnos?) both from Vega de Escalone and Puerta Curaco. Arthropod trackways include both some with differentiated (Diplichnites?) and other specimen with undifferentiated appendages. In the indicatives of subaerial exposure in sections expected to be fully marine. Complex traces assigned to Hillichnus produced by tellinacean bivalves are the only record of such bivalves in the basin. Those ichnogenera are good examples that precede body fossil records and along with the scratch marks suggest very unexpected according to paleogeographic maps. Finally a brief analysis of the further work in the turbidites of the Molles Formation or the exploration of bioerosion and meiofauna records suggest that the knowledge about the ichnology of the Neuquén Basin is in its infancy if it is compared with the stratigraphic, paleontologic (biostratigraphic) and sedimentologic studies and also remains unexplored related to changes in permeability of reservoirs of bioturbated deposits documented from cores.
Revista de la Asociación Geológica Argentina, Oct 1, 2009
En este trabajo se realiza una síntesis icnológica de las unidades marinas de la cuenca Neuquina ... more En este trabajo se realiza una síntesis icnológica de las unidades marinas de la cuenca Neuquina teniendo en cuenta el marco estratigráfico de los hallazgos, se presentan nuevos datos y se mencionan aquellos aspectos aún no abordados. Los registros más antiguos han sido documentados en el Jurásico y contienen icnotaxones (Lapispira) que han sido descriptos por primera vez para Sudamérica en facies de plataforma. Otros constituyen un muy buen ejemplo de trazas bien preservadas en depósitos deltaicos jurásicos de la Formación Lajas, con influencia mareal. Allí, el registro incluye Asterosoma, Asteriacites, Dactyloidites, Diplocraterion, Gyrochorte, Palaeophycus, Polykladichnus, Schaubcilindrichnus, Siphonichnus, Thalassinoides, Teichichnus y trazas poco frecuentes en ambientes marinos someros como Helminthorhaphe y rizolitos, entre otras, indicativas de un complejo engranaje de facies. Los carbonatos jurásicos de la Formación La Manga contienen tempestitas con Dactyloidites, Gyrochorte, Jamerosonichnites y Thalassinoides, en Bardas Blancas. El registro icnológico del Cretácico Inferior se halla documentado en las Formaciones Mulichinco y Agrio. En la primera los icnofósiles aparecen en la zona de Vega de Escalone y comprenden Asteriacites, Lockeia, Ophiomorpha, Gyrochorte y posiblemente Bergaueria. En la Formación Agrio, tanto en Bajada del Agrio (localidad tipo) como en otras localidades dispersas en la cuenca aparecen icnofósiles tales como Gyrochorte, Ophiomorpha, Thalassinoides y Teichichnus. Nuevo material proveniente de ambas unidades incluye scratchs subácueos o de arrastre de vertebrados (Characichnos?) provenientes de las localidades de Vega de Escalone y Puerta Curaco. Las trazas de locomoción de artrópodos incluyen formas con apéndices diferenciados (Diplichnites?) e indiferenciados. En la Formación Agrio se reconocieron huellas tridáctilas de terópodos en el anticlinal cerro Rayoso, que confirman exposición subaérea en una zona hasta el presente interpretada como cercana al depocentro de la cuenca. En Mina La Continental se han documentado trazas complejas atribuibles a bivalvos tellínidos asignables a Hillichnus. En la mencionada localidad, aparecen huellas de terópodos. Éstas, como las de tellínidos anteceden el registro de fósiles corpóreos, que marcan condiciones de somerización extrema hasta exposición subaérea, lo que muestra claramente el valor de los estudios icnológicos en las interpretaciones paleoambientales, particularmente en sucesiones donde otros tipos de fósiles se hallan ausentes. Quedan numerosos intervalos marinos y unidades que aún no han sido estudiados, pero sin duda uno de los más interesantes se halla en la Formación Molles de naturaleza turbidítica o hiperpícnica, de la que no se conocen datos icnológicos. Del mismo modo son casi inexistentes los estudios de bioerosión y registros de trazas producidas por la meiofauna. Por todo ello, el conocimiento icnológico de los intervalos marinos de la cuenca Neuquina está en su infancia, si se lo compara con estudios paleontológicos de tipo bioestratigráfico, sedimentológicos o de rutina en la industria del petróleo tanto en afloramiento como en coronas.
Dr. Renato Rodolfo Andreis: (1935-2009)
Revista de la Asociación Geológica Argentina, Jan 10, 2009
Sintesis icnológica de unidades mesozoicas marinas de la Cuenca Neuquina, nuevos datos y perspectivas
Revista de la Asociación Geológica Argentina, Oct 1, 2009
ABSTRACT Ichnological synthesis of the marine units of the Neuquén Basin, new data and future per... more ABSTRACT Ichnological synthesis of the marine units of the Neuquén Basin, new data and future perspectives. In this paper the ichnology of the marine intervals of the Neuquén Basin is reviewed, taking into account an stratigraphic framework and discussing previous works on ichnology that contain some ichnogenera (Lapispira) that are firstly documented in South America in Jurassic of the Río Atuel area, and other ichnogenera that constitute well preserved records in the Jurassic tidal influenced deltas of the Lajas Formation. The trace fossil record includes Asterosoma, Asteriacites, Dactyloidites, Diplocraterion, Gyrochorte, Palaeophycus, Polykladichnus, Schaubcilindrichnus, Siphonichnus, Thalassinoides, Teichichnus and rare traces in shallow marine deposits like Helminthorhaphe and root traces indicative of a very complex facies scheme. A special mention deserves the traces from the carbonates of the La Manga Formation at Bardas Blancas, that contain ichnogenera like Dactyloidites, Gyrochorte, Jamerosonichnites and Thalassinoides recorded in tempestites. The Lower Cretaceous record documented in the Mulichinco and Agrio Formation is composed of Asteriacites, Gyrochorte, Lockeia, Ophiomorpha, and possibly Bergaueria, documented in the Mulichinco Formation at Vega de Escalone locality. Other traces described in the Agrio Formation are Gyrochorte, Ophiomorpha, Thalassinoides, Teichichnus among others of dubious assignation recorded at Bajada del Agrio and other areas of the basin. New material coming from both units includes subaqueous vertebrate scratchs (Characichnos?) both from Vega de Escalone and Puerta Curaco. Arthropod trackways include both some with differentiated (Diplichnites?) and other specimen with undifferentiated appendages. In the indicatives of subaerial exposure in sections expected to be fully marine. Complex traces assigned to Hillichnus produced by tellinacean bivalves are the only record of such bivalves in the basin. Those ichnogenera are good examples that precede body fossil records and along with the scratch marks suggest very unexpected according to paleogeographic maps. Finally a brief analysis of the further work in the turbidites of the Molles Formation or the exploration of bioerosion and meiofauna records suggest that the knowledge about the ichnology of the Neuquén Basin is in its infancy if it is compared with the stratigraphic, paleontologic (biostratigraphic) and sedimentologic studies and also remains unexplored related to changes in permeability of reservoirs of bioturbated deposits documented from cores.
Trace fossils and facies in glacial to postglacial deposits from the Paganzo basin (Late Carboniferous),central Precordillera, Argentina
Ameghiniana, 2000
Sitio de la Asociación Peleontológica Argentina.
Trace fossils and facies in glacial to postglacial deposits from the Paganzo basin (Late Carboniferous),central Precordillera, Argentina
Ameghiniana, 2000
Sitio de la Asociación Peleontológica Argentina.
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Papers by Pablo J . Pazos