The Cambrian-Ordovician siliciclastic platform of the Balcarce Formation (Tandilia System, Argentina): Facies, trace fossils, palaeoenvironments and sequence stratigraphy

The Lower Palaeozoic sedimentary cover of the Tandilia (Balcarce Formation) is made up of thick quartz arenite beds together with kaolinitic claystones and thin fine-grained conglomerates. The Balcarce Formation was formed in the nearshore and inner shelf environments of a tide-dominated and storm influenced open platform. It shows many features suggesting tidal sedimentation. Coarse-grained facies were formed by sand bar migration and accretion. Heterolithic packages are interpreted as interbar (swale) deposits. Subordinated HCS sandstones indicate storm events. The recognition of thick progradational clinoforms allows to confirm that the Balcarce sea was open to the south, as suggested years ago through palaeocurrent interpretation. The great abundance and variety of trace fossils is among the most outstanding characteristics of this unit. The ichnotaxa that have been recognised so far are: Ancorichnus ancorichnus, Arthrophycus alleghaniensis, Arthrophycus isp., Bergaueria isp., Cochlichnus isp., Conostichus isp., Cruziana furcifera, Cruziana isp., Daedalus labeckei, Didymaulichnus lyelli, Didymaulichnus isp., Diplichnites isp., Diplocraterion isp., Herradurichnus scagliai, ?Monocraterion isp., Monomorphichnus isp., Palaeophycus alternatus, Palaeophycus tubularis, Palaeophycus isp., Phycodes aff. pedum, Phycodes isp., Plagiogmus isp., Planolites isp., Rusophycus isp., Scolicia isp. and Teichichnus isp. Trace fossils have traditionally been used to assign the Balcarce Formation to the Lower Ordovician, due to the presence of Cruziana furcifera. However, Plagiogmus is typical of Cambrian successions world-wide

Dating the Triassic continental rift in the southern Andes: the Potrerillos Formation, Cuyo Basin, Argentina

The Triassic successions of western Argentina commonly show thin pyroclastic levels intercalated within thick fluvial and lacustrine terrigenous deposits. The Potrerillos Formation is the thickest Triassic unit in the Cuyo Basin. It is composed of alternating cycles of gravelly- sandy- and muddy-dominated intervals, in which several laterally-continuous tuff horizons occur. U-Pb SHRIMP ages were determined on zircon grains from three tuff levels located between the lowermost and the middle sections of the Potrerillos Formation. The ages for the time of deposition of the tuffs are 239.2 ± 4.5 Ma, 239.7 ± 2.2 Ma and 230.3 ± 2.3 Ma (Middle Triassic). Chemical data indicate that these acid to intermediate volcaniclastic rocks are derived from coeval basic magmas displaying tholeiitic to slightly alkaline signatures. They are associated with the rift stage that followed the extensive post-orogenic volcanism of the Choiyoi Group, that in turn has been ascribed to slab break-off in neighbouring areas. Two of the studied samples also record a subpopulation of inherited zircon grains with crystallisation ages of 260-270 Ma. The latter are considered to be an indirect measurement for the age of the Choiyoi Group in the Cuyo basin. The rift-related Triassic event represents the culmination of the Gondwanian magmatic cycle, and is interpreted as the result of subduction cessation and anomalous heating of the upper mantle previous to the western Gondwana break-up

The Cambrian-Ordovician siliciclastic platform of the Balcarce Formation (Tandilia System, Argentina) : Facies, trace fossils, palaeoenvironments and sequence stratigraphy

The Lower Palaeozoic sedimentary cover of the Tandilia (Balcarce Formation) is made up of thick quartz arenite beds together with kaolinitic claystones and thin fine-grained conglomerates. The Balcarce Formation was formed in the nearshore and inner shelf environments of a tide-dominated and storm influenced open platform. It shows many features suggesting tidal sedimentation. Coarse-grained facies were formed by sand bar migration and accretion. Heterolithic packages are interpreted as interbar (swale) deposits. Subordinated HCS sandstones indicate storm events. The recognition of thick progradational clinoforms allows to confirm that the Balcarce sea was open to the south, as suggested years ago through palaeocurrent interpretation. The great abundance and variety of trace fossils is among the most outstanding characteristics of this unit. The ichnotaxa that have been recognised so far are: Ancorichnus ancorichnus, Arthrophycus alleghaniensis, Arthrophycus isp., Bergaueria isp., Cochlichnus isp., Conostichus isp., Cruziana furcifera, Cruziana isp., Daedalus labeckei, Didymaulichnus lyelli, Didymaulichnus isp., Diplichnites isp., Diplocraterion isp., Herradurichnus scagliai, ?Monocraterion isp., Monomorphichnus isp., Palaeophycus alternatus, Palaeophycus tubularis, Palaeophycus isp., Phycodes aff. pedum, Phycodes isp., Plagiogmus isp., Planolites isp., Rusophycus isp., Scolicia isp. and Teichichnus isp. Trace fossils have traditionally been used to assign the Balcarce Formation to the Lower Ordovician, due to the presence of Cruziana furcifera. However, Plagiogmus is typical of Cambrian successions world-wide

The Late Palaeozoic of Western Gondwana: New insights from South American records

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Internal anatomy of an erg sequence from the aeolian-fluvial system of the De La Cuesta Formation (Paganzo Basin, northwestern Argentina)

Permian red beds of the De La Cuesta Formation in the Sierra de Narváez (Paganzo Basin, northwestern Argentina) are essentially composed of sandstones associated with mudstones and subordinate conglomerates. Facies distributions and stacking patterns indicate that these sediments resulted from the interaction between aeolian and ephemeral fluvial systems, and are represented by aeolian dune, dry aeolian interdune and aeolian sand sheet, mudflat, wet aeolian interdune, and fluvial deposits. The De La Cuesta Formation is characterised by aeolian (erg) sequences alternating with non-aeolian (terminal alluvial fan – mudflat) sequences. Each erg sequence is bounded at its base by a regionally extensive sand-drift surface and at the top by an extinction surface. A number of architectural elements, including aeolian dunes limited by interdunes, grouped crescentic aeolian dunes, longitudinal dunes, and draa with superimposed crescentic dunes are recognised in the erg sequences. The sand sea developed during phases of increasing aridity, whereas non-aeolian deposition might have occurred during more humid phases. Thus, the styles of aeolian-fluvial interaction are considered to result from cyclical climatic changes. Within the drier hemicycles, the rhythmic alternation between draa deposits and aeolian dune and interdune deposits indicates higher frequency cycles that could be attributed to subtle climatic oscillations and/ or changes in sand supply and availability. The development of the Permian sand sea in the inland Paganzo Basin seems to be related to the growth of a volcanic chain to the west. This topographic barrier separated the Paganzo Basin from the Chilean Basin, located along the western margin of Gondwana and characterised by shallow marine carbonate sedimentation. The correlation between the Permian erg and the shallow marine carbonates suggests a regional warming period during the Middle Permian in western Gondwana

The Cambrian-Ordovician siliciclastic platform of the Balcarce Formation (Tandilia System, Argentina) : Facies, trace fossils, palaeoenvironments and sequence stratigraphy

The Lower Palaeozoic sedimentary cover of the Tandilia (Balcarce Formation) is made up of thick quartz arenite beds together with kaolinitic claystones and thin fine-grained conglomerates. The Balcarce Formation was formed in the nearshore and inner shelf environments of a tide-dominated and storm influenced open platform. It shows many features suggesting tidal sedimentation. Coarse-grained facies were formed by sand bar migration and accretion. Heterolithic packages are interpreted as interbar (swale) deposits. Subordinated HCS sandstones indicate storm events. The recognition of thick progradational clinoforms allows to confirm that the Balcarce sea was open to the south, as suggested years ago through palaeocurrent interpretation. The great abundance and variety of trace fossils is among the most outstanding characteristics of this unit. The ichnotaxa that have been recognised so far are: Ancorichnus ancorichnus, Arthrophycus alleghaniensis, Arthrophycus isp., Bergaueria isp., Cochlichnus isp., Conostichus isp., Cruziana furcifera, Cruziana isp., Daedalus labeckei, Didymaulichnus lyelli, Didymaulichnus isp., Diplichnites isp., Diplocraterion isp., Herradurichnus scagliai, ?Monocraterion isp., Monomorphichnus isp., Palaeophycus alternatus, Palaeophycus tubularis, Palaeophycus isp., Phycodes aff. pedum, Phycodes isp., Plagiogmus isp., Planolites isp., Rusophycus isp., Scolicia isp. and Teichichnus isp. Trace fossils have traditionally been used to assign the Balcarce Formation to the Lower Ordovician, due to the presence of Cruziana furcifera. However, Plagiogmus is typical of Cambrian successions world-wide

Verificación de modelos de producción de sedimentos en cuencas del N.O. argentino

[ES] La erosión en cuencas es uno de los problemas ambientales más complejos a nivel mundial. Es así que ha sido tema de investigación durante décadas en los países con los más variados climas, y considerando una diversidad de factores tales como: amplios rangos de temperaturas, distribución temporal y espacial irregular de las lluvias, degradación de la cobertura vegetal, entre otros. Las metodologías desarrolladas (USLE, MUSLE, WEPP, etc.) y aplicadas principalmente en Estados Unidos y en Europa, tienen la limitación de ser aplicables bajo ciertas condiciones, por ejemplo: zonas agrícolas con los factores controlados, cuencas de superficies pequeñas (menores a 500 km2), disponibilidad de datos hidrológicos a nivel diario y en un período de tiempo representativo, entre las más importantes y con variables difícilmente de ser aplicadas de manera distribuida. En la mayoría de los casos su aplicación no es sencilla por el elevado número de parámetros y en ciertas instancias de planes de aprovechamiento hídrico (por ejemplo, estudios de factibilidad de sistemas de embalses) se requiere de una estimación expeditiva del aporte global potencial de sólidos al reservorio y no de una, modelación detallada. En el presente trabajo se analiza el comportamiento de una serie de modelos a escala distribuida (Gravilovic, USLE y Miraki) en un conjunto de cuencas en la región del Noroeste Argentino. Se utilizan para su validación los datos disponibles de relevamientos batimétricos de sus embalses, de manera de establecer los criterios de aplicación de cada metodología según el caso de estudio a tratar.Olmos, L.; Spalletti, P.; Farias, H.; Pilán, M. (2008). Verificación de modelos de producción de sedimentos en cuencas del N.O. argentino. Ingeniería del agua. 15(2):61-72. https://doi.org/10.4995/ia.2008.2926OJS6172152Aguirre Pe, J., (1988). Hidráulica de Sedimentos. Universidad de los Andes, Mérida, Venezuela.Bolton P., Bradbury P.A., Lawrence P. y Atkinson E., (1995). CALSITE V-3.1 - User Manual. HR Wallingford Ltd., Wallinford, United Kingdom.Clarke, C. y Waldo, P., (1986). Sediment Yield from Small and Medium Watersheds. Proceedings of the Fourth Federal Interagency Sedimentation Conference, Vol. I, USA.Emmanouloudis, D., y Filippidis, E., (2000). A quantitative estimation model of mountainous watersheds degradation. Technological University of Kavala, special edition, Greece.Fernández, R., Dasso C. y López F., (1998). Evaluación de Metodologías para la Estimación de la Erosión Hídrica Superficial en Cuencas Hídricas de la República Argentina. Anales XVII Congreso Nacional de Agua, Santa Fe, Argentina.Garde, R.J. y Ranga-Raju, K., (1985). Mechanics of Sediment Transportation and Alluvial Stream Problems. Halsted Press, J. Wiley & Sons, NY, USA.Olmos, L. y Jegat, H., (2001). Análisis de la erosión hídrica mediante un modelo distribuido (CALSITE) y un modelo agregado (SWRRB). Aplicación a la cuenca del río Grande (Venezuela), Ingeniería del Agua, 8(1), Valencia, España.Olmos, L., Borsellino, M.J., Mattar, M.T., Pilán, M.T. y Farias H.D., (2003). Estimación de la Tasa de Producción de Sedimentos en la Cuenca del Río Horcones (Prov. de Salta y Santiago del Estero). Nuevas Tendecias en Hidráulica de Rios, J.D. Brea & H.D. Farias (eds.), Buenos Aires, Argentina.Olmos, L.A., Spalletti, P., Farias, H.D. y Pilán, M.T., (2004) Estudio y verificación del modelo de producción de sedimentos en cuencas de Miraki a escala distribuida. XXI Congreso Latinoamericano de Hidráulica, Sáo Paulo, Brasil, Octubre.Spalletti, P.D. y Brea, J.D., (2000). Validación de una metodología para estimación de producción de sedimentos. Memorias XVIII Congreso Nacional del Agua, Santiago del Estero, Argentina.Wischmeier, W. y Smith, D., (1978). Predicting Rainfall Erosion Losses. USDA & Agricultural Research Service, Agriculture Handbook No.282, USA

Sedimentology, palaeobotany and geochronology of the Piedra del Aguila Formation (Lower Jurassic, Neuquen) [Consideraciones acerca de la sedimentologia, paleobotanica y geocronologia de la Formacion Piedra del Aguila (Jurasico Inferior, Neuquan)]

At its type locality, the Piedra del Águila Formation is a 71.6 m thick homoclinal succession that lies on a weathering palaeosurface developed on the igneous-metamorphic basement (Mamil Choique Formation), and is unconformably covered by the Lower Jura

Archean to Recent aeolian sand systems and their preserved successions: current understanding and future prospects

The sedimentary record of aeolian sand systems extends from the Archean to the Quaternary, yet current understanding of aeolian sedimentary processes and product remains limited. Most preserved aeolian successions represent inland sand-sea or dunefield (erg) deposits, whereas coastal systems are primarily known from the Cenozoic. The complexity of aeolian sedimentary processes and facies variability are under-represented and excessively simplified in current facies models, which are not sufficiently refined to reliably account for the complexity inherent in bedform morphology and migratory behaviour, and therefore cannot be used to consistently account for and predict the nature of the preserved sedimentary record in terms of formative processes. Archean and Neoproterozoic aeolian successions remain poorly constrained. Palaeozoic ergs developed and accumulated in relation to the palaeogeographical location of land masses and desert belts. During the Triassic, widespread desert conditions prevailed across much of Europe. During the Jurassic, extensive ergs developed in North America and gave rise to anomalously thick aeolian successions. Cretaceous aeolian successions are widespread in South America, Africa, Asia, and locally in Europe (Spain) and the USA. Several Eocene to Pliocene successions represent the direct precursors to the present-day systems. Quaternary systems include major sand seas (ergs) in low-lattitude and mid-latitude arid regions, Pleistocene carbonate and Holocene–Modern siliciclastic coastal systems. The sedimentary record of most modern aeolian systems remains largely unknown. The majority of palaeoenvironmental reconstructions of aeolian systems envisage transverse dunes, whereas successions representing linear and star dunes remain under-recognized. Research questions that remain to be answered include: (i) what factors control the preservation potential of different types of aeolian bedforms and what are the characteristics of the deposits of different bedform types that can be used for effective reconstruction of original bedform morphology; (ii) what specific set of controlling conditions allow for sustained bedform climb versus episodic sequence accumulation and preservation; (iii) can sophisticated four-dimensional models be developed for complex patterns of spatial and temporal transition between different mechanisms of accumulation and preservation; and (iv) is it reasonable to assume that the deposits of preserved aeolian successions necessarily represent an unbiased record of the conditions that prevailed during episodes of Earth history when large-scale aeolian systems were active, or has the evidence to support the existence of other major desert basins been lost for many periods throughout Earth history