Patagonia: where does it come from?

Based on the recent finding of archeocyathids in molassic middle Cambrian to Early Ordovician age-sequences of northern Patagonia the relationships between this southern part of South America and East Antarctica need to be re-examined. The early Cambrian age of the archeocyathids, and their derivation from the Shackleton Limestones, open several alternatives that are evaluated based on the lithology and the U-Pb zircon ages of the different metamorphic sequences of Patagonia and the Transantarctic Mountains. Based on these data, it is proposed that the Somuncurá Massif of northern Patagonia is the conjugate margin of the Pensacola Mountains in East Antarctica. The main episodes of deformation within the Cambrian-Ordovician Ross Orogeny are correlated, as well as the passive margin setting during the Silurian-Devonian, which indicate that the lower section of the Beacon Supergroup of Antarctica corresponds to the Sierra Grande Formation in Patagonia. These facts show that the Patagonian terrane may have been situated as the conjugate margin of the Transantarctic Mountains from Southern Victoria Land to the Pensacola Mountains. The rifting of Patagonia from Antarctica and the beginning of subduction along western Patagonia, are correlated among different terranes, showing a robust coherent evolution through early Paleozoic times among these blocks. The final amalgamation of Patagonia with Western Gondwana occurred in late Paleozoic times, but is not analyzed in the present contribution.Sobre la base de hallazgos recientes de arqueociátidos en depósitos molásicos de edad cámbrica media a ordovícica temprana del norte de la Patagonia, las relaciones entre esta parte del sur de Sudamérica y Antártida Oriental necesitan ser reexaminadas. La edad cámbrica temprana de los arqueociátidos y su derivación de las Calizas Shackleton abren varias alternativas que son evaluadas sobre la base de la litología y las edades U-Pb en circones de diferentes secuencias metamórficas de la Patagonia y de las Montañas Trasantárticas. Sobre la base de estos datos se propone que el Macizo de Somuncurá del norte de la Patagonia fue el margen conjugado de las Montañas Pensacola de Antártida Oriental. Los episodios principales de deformación son correlacionados dentro del orógeno Ross del Cámbrico-Ordovícico, así como el ambiente de margen pasivo durante el Silúrico y el Devónico que indica que la sección inferior del Supergrupo Beacon de Antártida se corresponde con la Formación Sierra Grande de Patagonia. Estos datos muestran que el terreno Patagonia podría haber estado situado como el margen conjugado de las Montañas Trasantárticas desde el sur de la Tierra Victoria hasta las Montañas Pensacola. El rifting de Patagonia de Antártida y el inicio de la subducción a lo largo del oeste de la Patagonia se correlacionan entre diferentes terrenos mostrando una evolución coherente y robusta a lo largo del Paleozoico temprano entre estos bloques. El amalgamiento final de la Patagonia con el Gondwana Occidental se produjo en el Paleozoico tardío, pero no es analizado en la presente contribución.Fil: Ramos, Victor Alberto. 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: Naipauer, Maximiliano. 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

Patagonia: where does it come from?

Based on the recent finding of archeocyathids in molassic middle Cambrian to Early Ordovician age-sequences of northern Patagonia the relationships between this southern part of South America and East Antarctica need to be re-examined. The early Cambrian age of the archeocyathids, and their derivation from the Shackleton Limestones, open several alternatives that are evaluated based on the lithology and the U-Pb zircon ages of the different metamorphic sequences of Patagonia and the Transantarctic Mountains. Based on these data, it is proposed that the Somuncurá Massif of northern Patagonia is the conjugate margin of the Pensacola Mountains in East Antarctica. The main episodes of deformation within the Cambrian-Ordovician Ross Orogeny are correlated, as well as the passive margin setting during the Silurian-Devonian, which indicate that the lower section of the Beacon Supergroup of Antarctica corresponds to the Sierra Grande Formation in Patagonia. These facts show that the Patagonian terrane may have been situated as the conjugate margin of the Transantarctic Mountains from Southern Victoria Land to the Pensacola Mountains. The rifting of Patagonia from Antarctica and the beginning of subduc­tion along western Patagonia, are correlated among different terranes, showing a robust coherent evolution through early Paleozoic times among these blocks. The final amalgamation of Patagonia with Western Gondwana occurred in late Paleozoic times, but is not analyzed in the present contribution.Sobre la base de hallazgos recientes de arqueociátidos en depósitos molásicos de edad cámbrica media a ordovícica temprana del norte de la Patagonia, las relaciones entre esta parte del sur de Sudamérica y Antártida Oriental necesitan ser reexaminadas. La edad cámbrica temprana de los arqueociátidos y su derivación de las Calizas Shackleton abren varias alternativas que son evaluadas sobre la base de la litología y las edades U-Pb en circones de diferentes secuencias metamórficas de la Patagonia y de las Montañas Trasantárticas. Sobre la base de estos datos se propone que el Macizo de Somuncurá del norte de la Patagonia fue el margen conjugado de las Montañas Pensacola de Antártida Oriental. Los episodios principales de deformación son correlacionados dentro del orógeno Ross del Cámbrico-Ordovícico, así como el ambiente de margen pasivo durante el Silúrico y el Devónico que indica que la sección inferior del Supergrupo Beacon de Antártida se corresponde con la Formación Sierra Grande de Patagonia. Estos datos muestran que el terreno Patagonia podría haber estado situado como el margen conjugado de las Montañas Trasantárticas desde el sur de la Tierra Victoria hasta las Montañas Pensacola. El rifting de Patagonia de Antártida y el inicio de la subducción a lo largo del oeste de la Patagonia se correlacionan entre diferentes terrenos mostrando una evolución coherente y robusta a lo largo del Paleozoico temprano entre estos bloques. El amalgamiento final de la Patagonia con el Gondwana Occidental se produjo en el Paleozoico tardío, pero no es analizado en la presente contribución

Patagonia: where does it come from?

Based on the recent finding of archeocyathids in molassic middle Cambrian to Early Ordovician age-sequences of northern Patagonia the relationships between this southern part of South America and East Antarctica need to be re-examined. The early Cambrian age of the archeocyathids, and their derivation from the Shackleton Limestones, open several alternatives that are evaluated based on the lithology and the U-Pb zircon ages of the different metamorphic sequences of Patagonia and the Transantarctic Mountains. Based on these data, it is proposed that the Somuncurá Massif of northern Patagonia is the conjugate margin of the Pensacola Mountains in East Antarctica. The main episodes of deformation within the Cambrian-Ordovician Ross Orogeny are correlated, as well as the passive margin setting during the Silurian-Devonian, which indicate that the lower section of the Beacon Supergroup of Antarctica corresponds to the Sierra Grande Formation in Patagonia. These facts show that the Patagonian terrane may have been situated as the conjugate margin of the Transantarctic Mountains from Southern Victoria Land to the Pensacola Mountains. The rifting of Patagonia from Antarctica and the beginning of subduction along western Patagonia, are correlated among different terranes, showing a robust coherent evolution through early Paleozoic times among these blocks. The final amalgamation of Patagonia with Western Gondwana occurred in late Paleozoic times, but is not analyzed in the present contribution.Sobre la base de hallazgos recientes de arqueociátidos en depósitos molásicos de edad cámbrica media a ordovícica temprana del norte de la Patagonia, las relaciones entre esta parte del sur de Sudamérica y Antártida Oriental necesitan ser reexaminadas. La edad cámbrica temprana de los arqueociátidos y su derivación de las Calizas Shackleton abren varias alternativas que son evaluadas sobre la base de la litología y las edades U-Pb en circones de diferentes secuencias metamórficas de la Patagonia y de las Montañas Trasantárticas. Sobre la base de estos datos se propone que el Macizo de Somuncurá del norte de la Patagonia fue el margen conjugado de las Montañas Pensacola de Antártida Oriental. Los episodios principales de deformación son correlacionados dentro del orógeno Ross del Cámbrico-Ordovícico, así como el ambiente de margen pasivo durante el Silúrico y el Devónico que indica que la sección inferior del Supergrupo Beacon de Antártida se corresponde con la Formación Sierra Grande de Patagonia. Estos datos muestran que el terreno Patagonia podría haber estado situado como el margen conjugado de las Montañas Trasantárticas desde el sur de la Tierra Victoria hasta las Montañas Pensacola. El rifting de Patagonia de Antártida y el inicio de la subducción a lo largo del oeste de la Patagonia se correlacionan entre diferentes terrenos mostrando una evolución coherente y robusta a lo largo del Paleozoico temprano entre estos bloques. El amalgamiento final de la Patagonia con el Gondwana Occidental se produjo en el Paleozoico tardío, pero no es analizado en la presente contribución.Fil: Ramos, Victor Alberto. 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: Naipauer, Maximiliano. 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

Late Cenozoic contractional evolution of the current arc-volcanic region along the southern Central Andes (35°20′S)

The Andean internal zone records deformation, uplift and erosion that serve as proxies of variations on mountain building dynamics. Hence, the study of this region would give keys to understand the factors controlling the orogenic evolution. Structural, stratigraphic and geochronological data in the Andean internal zone at 35°20′S evidence that this region has only underwent contractional deformation since the late Miocene up to present, differing from coeval Pleistocene extensional tectonics affecting the retro-arc. Contractional deformation was characterized by the development of a piggy-back basin in the latest Miocene filled by synorogenic deposits. Afterward, an out-of-sequence thrusting event affected the region since at least the Pliocene until the Present. Shortening in the inner part of the Andean orogen would be favored by both the high orthogonality of the out-sequence structures with respect to the plate convergence vector and by the minor resistance to shortening produced by the southward decrease of the orogen height and by the removal of material via erosion of the uplifted mountain belt. In contrast, oblique structures, as those described farther north, accommodate strike-slip displacement. Likewise, we propose that erosion from the inner orogen favored the prolongation of the out-of-sequence thrusting event until the Present, differing from the situation north of the 34°S where this event ended by the Pliocene.Fil: Tapia, Felipe. Universidad de Chile. Facultad de Ciencias Físicas y Matemáticas. Departamento de Geología; Chile. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Farías, Marcelo. Universidad de Chile. Facultad de Ciencias Físicas y Matemáticas. Departamento de Geología; ChileFil: Naipauer, Maximiliano. 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: Puratich, Jacqueline. Universidad de Chile. Facultad de Ciencias Físicas y Matemáticas. Departamento de Geología; Chil

The Malvinas (Falkland) Plateau derived from Africa?: Constraints for its tectonic evolution

The latest studies on the tectonic evolution of the Malvinas (Falkland) Islands and their adjacent continental plateau further east are analyzed to assess a long controversy regarding the origin of these islands. Although there has been a controversy for several decades on this subject, new technologies and exploratory drilling have brought new data, however the debate of the geological evolution of this area remains open. The two dominant hypotheses are analyzed by assessing the eventual collision between the islands and the South American continent, the presence of a large transcontinental fault such as Gastre, the potential 180º rotation of the Malvinas Islands, and the occurrence of a mega-decollement with opposite vergence. These hypotheses are contrasted with the processes that have occurred in Patagonia, especially those based on the new isotopic data on the Maurice Ewing Bank at the eastern end of the Malvinas Plateau, and the current knowledge of the adjacent Malvinas Basin. The new data highlights the inconsistencies of certain models that proposed these islands migrated from the eastern African coasts near Natal, to their current position and rotated 180º on a vertical axis. The new observations are consolidating the hypothesis that postulates that the islands have been part of the South American continent since before the Paleozoic.Fil: Ramos, Victor Alberto. 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 "Don Pablo Groeber"; ArgentinaFil: Chemale, Farid. Universidad de Vale do Rio dos Sinos; BrasilFil: Lovecchio, Juan Pablo. Yacimiento Petroliferos Fiscal S.a.; ArgentinaFil: Naipauer, Maximiliano. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geocronología y Geología Isotópica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geocronología y Geología Isotópica; Argentin

High-precision U-Pb ages in the early Tithonian to early Berriasian and implications for the numerical age of the Jurassic-Cretaceous boundary

The numerical age of the Jurassic-Cretaceous boundary has been controversial and difficult to determine. In this study, we present high-precision U-Pb geochronological data around the Jurassic-Cretaceous boundary in two distinct sections from different sedimentary basins: the Las Loicas, Neuquén Basin, Argentina, and the Mazatepec, Sierra Madre Oriental, Mexico. These two sections contain primary and secondary fossiliferous markers for the boundary as well as interbedded volcanic ash horizons, allowing researchers to obtain new radioisotopic dates in the late Tithonian and early Berriasian. We also present the first age determinations in the early Tithonian and tentatively propose a minimum duration for the stage as a cross-check for our ages in the early Berriasian. Given our radioisotopic ages in the early Tithonian to early Berriasian, we discuss implications for the numerical age of the boundary.Fil: Lena, Luis. Universidad de Ginebra; SuizaFil: López Martínez, Rafael. Universidad Nacional Autónoma de México; MéxicoFil: Lescano, Marina Aurora. 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 "Don Pablo Groeber"; ArgentinaFil: Aguirre-Urreta, Maria Beatriz. 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 "Don Pablo Groeber"; ArgentinaFil: Concheyro, Graciela. 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 "Don Pablo Groeber"; ArgentinaFil: Vennari, Verónica Vanesa. 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 "Don Pablo Groeber"; ArgentinaFil: Naipauer, Maximiliano. 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 "Don Pablo Groeber"; ArgentinaFil: Samankassou, Elias. Universidad de Ginebra; SuizaFil: Pimentel, Márcio. Universidade do Brasília; BrasilFil: Ramos, Victor Alberto. 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 "Don Pablo Groeber"; ArgentinaFil: Schaltegger, Urs. Universidad de Ginebra; Suiz

Archaeocyaths from South America: Review and a new record

In South America, autochthonous archaeocyathan faunas preserved in Early Cambrian limestones have not been found yet. Nevertheless, a few well-documented occurrences of these fossils in clasts contained in coarse-grained rocks of a wide age range have been discovered in recent years. Erratic limestone blocks from the Late Carboniferous-Early Permian Fitzroy Tillite Formation in the Falkland/Malvinas Islands yielded three archaeocyath taxa. Also, seven taxa were reported from archaeocyathan limestone clasts in a metaconglomerate of the Cambro-Ordovician El Jagüelito Formation in northern Patagonia. In addition, a new record from the Late Carboniferous-Early Permian Sauce Grande Formation diamictites in Sierras Australes, Buenos Aires Province, Argentina, is presented herein. Preservation of this scarce new material is poor, but at least three different taxa can be distinguished. The most likely source of all archaeocyathan limestone clasts found in southern South America is the Shackleton Limestone from the Transantarctic Mountains in East Antarctica. The new record from the Sauce Grande Formation and the inferred clast provenance reinforce the correlation between this unit, the Dwyka Tillite (South Africa) and the Fitzroy Tillite Formation (Falklands/Malvinas), suggesting a very wide distribution of these Antarctic occurrences during the Late Carboniferous-Early Permian Gondwana glaciation (Episode III). Thus, even though being allochthonous, archaeocyaths are emerging as a new key biological feature for Gondwana palaeogeographic reconstructions.Centro de Investigaciones GeológicasFacultad de Ciencias Naturales y Muse

Geochemistry of Precordillera serpentinites, western Argentina : evidence for multistage hydrothermal alteration and tectonic implications for the Neoproterozoic-early Paleozoic

Serpentinites are a powerful tool to evaluate mantle composition and subsequent alteration processes during their tectonic emplacement. Exposures of this type of rocks can be found in the Argentine Precordillera (Cuyania terrane) and Frontal Cordillera, both located in central-western Argentina, within the Central Andes. In these regions a Neoproterozoic to Devonian mafic-ultramafic belt composed of serpentinites, metabasaltic dikes/sills, pillow lavas (with an Enriched to Normal Mid-Ocean Ridge Basalts (E- to N-MORB) geochemical signature) and mafic granulites crop out, spatially associated with marine metasedimentary rocks. The serpentinite bodies consist of lizardite/chrysotile+brucite+magnetite, with scarce pentlandite and anhedral reddish-brown Cr-spinel (picotite, pleonaste and spinel sensu stricto) as relict magmatic phases. The original peridotites were moderately-depleted harzburgites (ultramafic cumulates) with an intermediate chemical signature between a mid-ocean ridge and an arc-related ophiolite. Whole-rock Rare Earth Elements (REE) patterns of serpentinites exhibit enriched REE patterns ((La/Yb)CN=13-59) regarding CI chondrite with positive Eu anomalies. These features are the result of an interaction between hydrothermal fluid and serpentinites, in which moderate temperature (350º-400ºC), CO2-rich, mildly basic hydrothermal fluid was involved and was responsible for the addition of Ca, Sr and REE to serpentinites. The presence of listvenites (silica-carbonate rocks) in the serpentinite margins allow us to infer another fluid metasomatism, where lowtemperatures (<250ºC), highly-oxidized, highly-acid fluid lead to the precipitation of silica. The association of these metasomatized serpentinite bodies with neoproterozoic continental margin sucessions and MORB magmatism at the suture zone of the Cuyania and Chilenia terranes suggests the development of an oceanic basin between them during the Neoproterozoic-early Paleozoic

Cretaceous deformation of the southern Central Andes: synorogenic growth strata in the Neuquén Group (35° 300–37° S)

The Neuquén Group is an Upper Cretaceous continental sedimentary unit exhumed during the latest Miocene contractional phase occurred in the southern Central Andes, allowing a direct field observation and study of the depositional geometries. The identification of growth strata on these units surrounding the structures of the frontal parts of the Andes, sedimentological analyses and U–Pb dating of detrital components, allowed the definition of a synorogenic unit that coexisted with the uplift of the early Andean orogen since ca. 100 Ma, maximum age obtained in this work, compatible with previous assignments and constrained in the top by the deposition of the Malarg€ue Group, in the Maastrichtian (ca. 72 Ma). The definition of a wedge top area in this foreland basin system, where growth strata were described, permitted to identify a Late Cretaceous orogenic front and foredeep area, whose location and amplitude contrast with previous hypotheses. This wedge top area was mostly fed from the paleo-Andes with small populations coming from sources in the cratonic area that are interpreted as a recycling in Jurassic and Lower Cretaceous sections, which contrasts with other analyses performed at the foredeep zone that have mixed sources. In particular, Permian sources are interpreted as coming directly from the cores of the basement structures, where Neopaleozoic sections are exposed, next to the synorogenic sedimentation, implying a strong incision in Late Cretaceous times with an exhumation structural level similar to the present. The maximum recognised advance for this Late Cretaceous deformation in the study area is approximately 500 km east of the Pacific trench, which constitutes an anomaly compared with neighbour segments where Late Cretaceous deformations were found considerably retracted. The geodynamic context of the sedimentation of this unit is interpreted as produced under the westward fast moving of South America, colliding with two consecutive mid-ocean ridges during a period of important plate reorganisation. The subduction of young, anhydrous, buoyant lithosphere would have produced changes in the subduction geometry, reflected first by an arc waning/gap and subsequently by an arc migration that coexisted with synorogenic sedimentation. These magmatic and deformational processes would be the product of a shallow subduction regime, following previous proposals, which occurred in Late Cretaceous times, synchronous to the sedimentation of the Neuqu en Group.Facultad de Ciencias Naturales y Muse

Strontium isotopic composition from Northeast Patagonia: Preliminary results

Se estudió la composición isotópica de estroncio de rocas calcáreas de unidades del Noreste patagónico. Incluye, a) mármoles de Pailemán (de dudosa pertenencia a la Formación El Jagüelito), valor medio de 87Sr/86Sr 0,707354 ± 0,000113; b) mármoles de Estancia La Auriciana (Complejo Mina Gonzalito), valor medio de 87Sr/86Sr 0,708730 ± 0,000285; c) clastos de calizas con arqueociátidos de un metaconglomerado de la Formación El Jagüelito en las proximidades de Sierra Grande, valor medio de 87Sr/86Sr 0,710605 ± 0,000118. El cotejo con la curva estándar de variación de 87Sr/86Sr en los mares en función del tiempo, ubica con mayor antigüedad a los mármoles de Pailemán (ca. 625 Ma), con una edad de ca. 550-510 Ma a los mármoles de Estancia La Auriciana y en el Cámbrico a las calizas de los clastos del metaconglomerado de Sierra Grande.We have carried out measurements of strontium isotopic compositions of carbonate units from northeastern Patagonia. The rock units included in the study are: a) Pailemán marble, with questionable belonging to El Jagüelito Formation, and mean 87Sr/86Sr value of 0.707354 ± 0.000113; b) marbles from estancia La Auriciana, Mina Gonzalito Complex, with mean 87Sr/86Sr value of 0.708730 ± 0.000285; c) archaeocyathan limestone clasts from a metaconglomerate layer of El Jagüelito Formation in the Sierra Grande area, with mean 87Sr/86Sr value of 0.710605 ± 0.000118. Comparison of these data with the global 87Sr/86Sr evolution curve suggests that the Pailemán marble is the oldest (ca. 625 Ma), followed by the estancia La Auriciana marbles (ca. 550-510 Ma), while the archeocyathan limestone clasts from Sierra Grande area are Cambrian.Fil: Varela, Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - la Plata. Centro de Investigaciones Geológicas. Universidad Nacional de la Plata. Facultad de Ciencias Naturales y Museo. Centro de Investigaciones Geológicas; ArgentinaFil: Gonzalez, Pablo Diego. Universidad Nacional de Rio Negro. Sede Alto Valle. Instituto de Investigaciones En Paleobiologia y Geologia; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Philipp, Ruy. Universidade Federal Do Rio Grande Do Sul; BrasilFil: Sato, Ana Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - la Plata. Centro de Investigaciones Geológicas. Universidad Nacional de la Plata. Facultad de Ciencias Naturales y Museo. Centro de Investigaciones Geológicas; ArgentinaFil: González, Santiago Nicolás. Universidad Nacional de Rio Negro. Sede Alto Valle. Instituto de Investigaciones En Paleobiologia y Geologia; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Greco, Gerson Alan. Universidad Nacional de Rio Negro. Sede Alto Valle. Instituto de Investigaciones En Paleobiologia y Geologia; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Naipauer, Maximiliano. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Geología. Laboratorio de Tectónica Andina; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin