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10. Occurrence of Cyclusphaera Scabrata in Achiri (Late Middle-Early Late Miocene?, Bolivian Altiplano): Paleogeographical Implication

Author

PRAMPARO, MERCEDES B., primary, Antoine, Pierre-Olivier, additional, Marivaux, Laurent, additional, Andrade Flores, Rubén, additional, Fernández-Monescillo, Marcos, additional, Boscaini, Alberto, additional, Mamani Quispe, Bernardino, additional, Fauquette, Séverine, additional, Bonnet, Colline, additional, Münch, Philippe, additional, and Pujos, François, additional

Published
2022
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11. The megatherioid sloth 'Xyophorus' villarroeli from the late Miocene of Achiri (Bolivia)

Author

Pujos, François, Gaudin, Timothy J., Boscaini, Alberto, Abello, M. Alejandra, Andrade Flores, Rubén, Fernandez-Monescillo, Marcos, Mamani Quispe, Bernardino, MARIVAUX, Laurent, Pramparo, Mercedes b., Antoine, Pierre-Olivier, Münch, Philippe, Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales [Mendoza] (CONICET-IANIGLA), Consejo Nacional de Investigaciones Científicas y Técnicas [Buenos Aires] (CONICET)-Universidad Nacional de Cuyo [Mendoza] (UNCUYO), Department of Biology, Geology and Environmental Science, University of Tennessee at Chattanooga, Instituto de Ecología, Genética y Evolución de Buenos Aires (IEGEBA), Consejo Nacional de Investigaciones Científicas y Técnicas [Buenos Aires] (CONICET)-Facultad de Ciencias Exactas y Naturales [Buenos Aires] (FCEyN), Universidad de Buenos Aires [Buenos Aires] (UBA)-Universidad de Buenos Aires [Buenos Aires] (UBA), Facultad de Ciencias Naturales y Museo [La Plata] (FCNyM), Universidad Nacional de la Plata [Argentine] (UNLP), Museo Nacional de Historia Natural de Bolivia (MNHN-Bol), Consejo Nacional de Investigaciones Científicas y Técnicas, Instituto Multidisciplinario de Biología Vegetal (IMBIV), and Factulad de Ciencias Exactas, Físicas y Naturales, Universidad Nacional de Córdoba, Córdoba, Argentina, Institut des Sciences de l'Evolution de Montpellier (UMR ISEM), École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Montpellier (UM)-Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Centre National de la Recherche Scientifique (CNRS)-Institut de recherche pour le développement [IRD] : UR226, Géosciences Montpellier, Institut national des sciences de l'Univers (INSU - CNRS)-Université de Montpellier (UM)-Université des Antilles (UA)-Centre National de la Recherche Scientifique (CNRS), PICT 2010-1805, MINCyT-ECOS A14U01, NGS 9971-16, and EC-44712R-18, and Asociación Paleontológica Argentina

Subjects
[SDU.STU.PG]Sciences of the Universe [physics]/Earth Sciences/Paleontology
Abstract

International audience; Miocene vertebrate localities are uncommon in central South America. In Bolivia, the best known mammalian faunas ofthis period come from Quebrada Honda (late middle Miocene, Tarija Department) and Cerdas (early middle Miocene, PotosíDepartment). The Achiri locality (La Paz Department) was reported first by Hoffstetter in 1972. Subsequently, campaignswere conducted in this locality by several paleontologists, including Villarroel, Anaya, Saint-André, and by our team over thelast decade. Recently, we have obtained two precise absolute dates (40Ar/39Ar) on feldspar contained in ashes intercalatedbetween fossiliferous levels and confirmed a late Miocene age (10.35±0.07 Ma and 10.42±0.09 Ma, late Mayoan–earlyChasicoan South American Land Mammal Ages) as suggested by Marshall and colleagues in 1983. Almost all the specimenscome from the Cerros Virgen Pata and Jiska/Jacha Pisakeri localities, the latter located 3–4 km southeast of Achiri village.In the past, discoveries of numerous spectacular specimens have allowed the identification of new mammalian speciessuch as the notoungulates Plesiotypotherium achirense and Hoffstetterius imperator, the sparassodontan Borhyaenidiumaltiplanicum, and the xenarthrans Trachycalyptoides achirense and Xyophorus villarroeli. Xyophorus was erected by Ameghinoin 1887 on the basis of a dentary fragment from the lower Miocene Santa Cruz Formation (Argentina). This taxon is generallyconsidered to be a nothrotheriid sloth (although has never been formally included in a phylogenetic analysis based onosteological characters). Six species are recognized in Argentina. This genus is also recorded in Achiri through the endemicspecies X. villarroeli, and also in Cerdas and Quebrada Honda through X. cf. bondesioi. Unfortunately, all the specimensreferred to Xyophorus are extremely fragmentary. Here we present a partial skull (MNHN-Bol-V 12690, National Museumof Natural History, La Paz, Bolivia) discovered in Achiri, belonging to an adult, and referred as “Xyophorus” villarroeli. Itconsists of a right posterolateral portion of the skull, including parts of squamosal, parietal, basioccipital, exoccipital, andits complete ear region with ectotympanic, entotympanic, and petrosal. Preliminary observations of this new specimenreveal the presence of at least seven autapomorphies, including a very rugose external surface of ectotympanic, a clearcontact between styliform process of ectotympanic and pterygoid, and a reduced or absent subarcuate fossa. Thismegatherioid sloth shares several synapomorphies with nothrotheriids, including a dorsoventrally elongated ectotympanicand an ovate stylohyal fossa. It exhibits also transitional features between basal megatherioids and nothrotheriids, like aventral portion of the ectotympanic that is expanded transversely in ventral view (more than Hapalops and less thanNothrotheriidae) and deeper in lateral view than that of Hapalops, although similar in proportions to Pronothrotherium andMionothropus. This specimen thus suggests that “Xyophorus” villarroeli could be an early-diverging nothrothere, withaffinities to Hapalops and also early Nothrotheriidae, and probably distinct from Xyophorus of more austral localities. Acomprehensive phylogenetic analysis of the Megatherioidea including this form from Achiri, Aymaratherium from the earlyPliocene of Pomata-Ayte, and Lakukullus and Hiskatherium from Quebrada Honda, should allow for a better understandingof the relationships among Patagonian and Andean Megatherioidea.

Published
2021

12. New data on the glyptodontid Trachycalyptoides from the late Miocene Bolivian locality of Achiri

Author

Pujos, François, González Ruiz, L. R., Gaudin, Timothy J., Abello, M. Alejandra, Andrade Flores, Rubén, Fernández‐Monescillo, Marcos, Mamani Quispe, Bernardino, MARIVAUX, Laurent, Pramparo, Mercedes b., Antoine, Pierre-Olivier, Münch, Philippe, Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales [Mendoza] (CONICET-IANIGLA), Consejo Nacional de Investigaciones Científicas y Técnicas [Buenos Aires] (CONICET)-Universidad Nacional de Cuyo [Mendoza] (UNCUYO), Universidad Nacional de la Patagonia San Juan Bosco - UNPSJB (ARGENTINA), Department of Biology, Geology and Environmental Science, University of Tennessee at Chattanooga, Facultad de Ciencias Naturales y Museo [La Plata] (FCNyM), Universidad Nacional de la Plata [Argentine] (UNLP), Museo Nacional de Historia Natural de Bolivia (MNHN-Bol), Consejo Nacional de Investigaciones Científicas y Técnicas, Instituto Multidisciplinario de Biología Vegetal (IMBIV), and Factulad de Ciencias Exactas, Físicas y Naturales, Universidad Nacional de Córdoba, Córdoba, Argentina, Institut des Sciences de l'Evolution de Montpellier (UMR ISEM), École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Montpellier (UM)-Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Centre National de la Recherche Scientifique (CNRS)-Institut de recherche pour le développement [IRD] : UR226, Géosciences Montpellier, Institut national des sciences de l'Univers (INSU - CNRS)-Université de Montpellier (UM)-Université des Antilles (UA)-Centre National de la Recherche Scientifique (CNRS), PICT 2010-1805, MINCyT-ECOS A14U01, NGS 9971-16, and EC-44712R-18, Asociación Paleontológica Argentina, and MARIVAUX, Laurent

Subjects
[SDU.STU.PG] Sciences of the Universe [physics]/Earth Sciences/Paleontology, [SDU.STU.PG]Sciences of the Universe [physics]/Earth Sciences/Paleontology
Abstract

International audience; Among armored xenarthrans, Glyptodontidae appears as one of the most peculiar and also characteristic groups of SouthAmerican mammals that inhabited this continent since at least the early Eocene until the end of the Pleistocene. Theirevolutionary history is particularly well documented in Patagonia, Central and North America, but less so in the tropics andcentral South America. In Bolivia during the Miocene epoch, this family is only recorded at the Laventan locality of QuebradaHonda, represented by cf. “Asterostemma”, “Propalaehoplophorus” andinus, and two sclerocalyptine species, the ?Colloncuranlocality of Nazareno represented by “Propalaehoplophorus” and ?Neothoracophorus, occurring in Choquecota, and the lateMayoan–early Chasicoan localities of Chokorasi and Achiri by a single species, Trachycalyptoides achirense. The late Miocenevertebrate locality of Achiri discovered in the early 70’s by the French paleontologist Hoffstetter, was explored by severalteams during the subsequent decades. Its mammalian fauna is particularly diverse with more than 20 taxa, includingmetatherians (i.e., Borhyaenidium), notoungulates (e.g., Hoffstetterius), litopterns, rodents (e.g., Prolagostomus), as well asxenarthrans sloths (e.g., “Xyophorus”) and cingulates (e.g., Trachycalyptoides). Trachycalyptoides was erected by Saint-Andréin 1996 on the basis on two dermal armors and caudal tubes, an incomplete skull, and a hemimandible. The abundantmaterial collected by our team during recent fieldwork, and the preliminary revision of the material housed in the museumsof La Paz and Paris, has allowed us to gather new information, specifically on the dentition, dorsal carapace, and caudal tubeon this peculiar glyptodontid. In Trachycalyptoides the presence of three lobes is well marked on certain upper and lowermolariforms, especially on the most posterior teeth (fourth to eighth molariforms), whereas their presence is doubtful onthe third teeth, and absent on the first and second teeth. The general structure of the osteoderms corresponds to apentagonal or hexagonal polygon with a “rosette” pattern (a central figure surrounded by peripheral figures) on the exposedsurface. The central and peripheral figures are elevated and separated by a sulcus. The subcircular central figure is slightlyconcave in the center. The peripheral figures are small and in a variable number according to region (ranging from 3–4 to12–15), with foramina at the intersection with the sulcus of the central figure. The caudal tube is conical and elongated andits apex is relatively acute. The ventral face is slightly convex and the dorsal face is flat. The distal portion of the tube isformed by two large right and left osteoderms. The latter are roughly quadrangular, rectangular proximally and quadratedistally. The osteoderms of the caudal tube lack peripheral figures. The molariforms, dorsal carapace, and caudal tube ofTrachycalyptoides show affinities with glyptodonts that have a simplified trilobate pattern in the anteriormost molariforms,a dorsal carapace formed by osteoderms with a “rosette” pattern, and a caudal tube formed by osteoderms withoutperipheral figures like Cochlops, Palaehoplophorus, Trachycalyptus, and Lomaphorus.

Published
2021

13. Los roedores caviomorphos (Rodentia, Hystricognathi) del Mioceno tardío de Achiri (Bolivia)

Author

Pérez, Maria E., Candela, Andriana M., Mamani Quispe, Bernardino, Abello, M. Alejandra, ADNET, Sylvain, Andrade Flores, Rubén, Billet, Guillaume, Boscaini, Alberto, Fernandez-Monescillo, Marcos, MARIVAUX, Laurent, Münch, Philippe, Pramparo, Mercedes b., Antoine, Pierre-Olivier, Museo Paleontológico Egidio Feruglio [Chubut] (MEF), Consejo Nacional de Investigaciones Científicas y Técnicas [Buenos Aires] (CONICET), Facultad de Ciencias Naturales y Museo [La Plata] (FCNyM), Universidad Nacional de la Plata [Argentine] (UNLP), Museo Nacional de Historia Natural de Bolivia (MNHN-Bol), Institut des Sciences de l'Evolution de Montpellier (UMR ISEM), École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Montpellier (UM)-Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Centre National de la Recherche Scientifique (CNRS)-Institut de recherche pour le développement [IRD] : UR226, Muséum national d'Histoire naturelle (MNHN), Museo Argentino de Ciencias Naturales ‘Bernardino Rivadavia' [Buenos Aires] (MACN), Universidad Nacional de Córdoba [Argentina], Géosciences Montpellier, Institut national des sciences de l'Univers (INSU - CNRS)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Université des Antilles (UA), Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales [Mendoza] (CONICET-IANIGLA), Consejo Nacional de Investigaciones Científicas y Técnicas [Buenos Aires] (CONICET)-Universidad Nacional de Cuyo [Mendoza] (UNCUYO), CONICET, NGS 9971-16 (EU), PICT 2010-1805 (Agencia, Argentina), y PIP 2015 (CONICET, Argentina), and MARIVAUX, Laurent

Subjects
[SDU.STU.PG] Sciences of the Universe [physics]/Earth Sciences/Paleontology, [SDU.STU.PG]Sciences of the Universe [physics]/Earth Sciences/Paleontology
Abstract

International audience; El conocimiento de los mamíferos neógenos de Bolivia se ha centrado principalmente en unos pocos yacimientos del Mioceno temprano (Cerdas, Nazareno) y el Mioceno medio (Quebrada Honda). En la última década, se han incrementado los esfuerzos de exploración, dando como resultado un mejor conocimiento de la fauna de la localidad de Achiri (Prov. de Pacajes) del Mioceno tardío (~10,42–9,42 Ma; Formación Mauri). Dentro de esta fauna, los especímenes de caviomorfos, depositados en la Unidad de Paleontología del Museo Nacional de Historia Natural de La Paz, son abundantes y consisten en restos cráneo-mandibulares y post-craneanos, y dientes aislados. El estudio preliminar indica la presencia de Prodolichotis prisca, Cardiomys sp. (Cavioidea), Tetrastylus sp., Lagostomus sp. (Chinchilloidea) y un octodontoideo indet. Prodolichotis abarca el 80% de la diversidad, con cráneos excepcionalmente preservados (varios asociados a mandíbulas). Los otros taxones están representados por especímenes que, aunque escasos y fragmentarios, permiten una asignación genérica clara (excepto el octodontoideo por su mala preservación). Prodolichotis prisca es el dolicotino más antiguo, registrado en el Mioceno tardío–Plioceno temprano del noroeste de Argentina. Cardiomys, Tetrastylus y Lagostomus se encuentran ampliamente distribuidos en niveles del Neógeno tardío de Argentina. Además, Tetrastylus se registra en el Mioceno tardío de Brasil, Uruguay y Venezuela. Aunque es necesario un análisis profundo de la taxonomía de los roedores de Achiri, los mismos indican mayor afinidad con las faunas de edad Chasiquense-Huayqueriense de Argentina. El estudio de esta asociación permitirá aumentar el conocimiento biogeográfico del Neógeno tardío de América del Sur.

Published
2021

15. A tropical palynoflora in the K-Pg Vilacapujio section, southwestern Bolivia

Author

Pramparo, Mercedes b., Narvaez, P., Mamani Quispe, Bernardino, Andrade flores, Ruben, ANTOINE, Pierre Olivier, MARIVAUX, Laurent, ADNET, Sylvain, Pujos, Francois, MARIVAUX, Laurent, Instituto Argentino de Nivolog, Glaciolog y Ciencias Ambientales, Universidad Nacional de Colombia [Bogotà] (UNAL), Museo Nacional de Historia Natural La Paz, Museo Nacional de Historia Natural, La Paz, Institut des Sciences de l'Evolution de Montpellier (UMR ISEM), École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Montpellier (UM)-Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Centre National de la Recherche Scientifique (CNRS)-Institut de recherche pour le développement [IRD] : UR226, Universidad Nacional de Colombia [Bogotá], Institut des Sciences de l'Evolution de Montpellier ( ISEM ), and Université de Montpellier ( UM ) -Institut de recherche pour le développement [IRD] : UR226-Centre National de la Recherche Scientifique ( CNRS )

Subjects
[ SDV.BV.BOT ] Life Sciences [q-bio]/Vegetal Biology/Botanics, [SDV.BV.BOT]Life Sciences [q-bio]/Vegetal Biology/Botanics, ComputingMilieux_MISCELLANEOUS, [SDV.BV.BOT] Life Sciences [q-bio]/Vegetal Biology/Botanics
Abstract

International audience

Published
2016

16. A strange nothrotheriid ground sloth (Xenarthra, Megatherioidea) from Pomata-Ayte (Miocene-Pliocene transition, Bolivia)

Author

Pujos , Francois, De iuliis , Gerardo, ADNET , Sylvain, Andrade flores , Ruben, Billet , Guillaume, Mamani Quispe , Bernardino, MARIVAUX , Laurent, Münch , Philippe, Pramparo , Mercedes b., ANTOINE , Pierre Olivier, MARIVAUX, Laurent, Instituto Argentino de Nivolog, Glaciolog y Ciencias Ambientales, University of Toronto, Institut des Sciences de l'Evolution de Montpellier ( ISEM ), Université de Montpellier ( UM ) -Institut de recherche pour le développement [IRD] : UR226-Centre National de la Recherche Scientifique ( CNRS ), Museo Nacional de Historia Natural, La Paz, Centre de recherche sur la Paléobiodiversité et les Paléoenvironnements ( CR2P ), Muséum National d'Histoire Naturelle ( MNHN ) -Université Pierre et Marie Curie - Paris 6 ( UPMC ) -Centre National de la Recherche Scientifique ( CNRS ), Museo Nacional de Historia Natural La Paz, Géosciences Montpellier, Université des Antilles et de la Guyane ( UAG ) -Institut national des sciences de l'Univers ( INSU - CNRS ) -Université de Montpellier ( UM ) -Centre National de la Recherche Scientifique ( CNRS ), Institut des Sciences de l'Evolution de Montpellier (UMR ISEM), École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Montpellier (UM)-Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Centre National de la Recherche Scientifique (CNRS)-Institut de recherche pour le développement [IRD] : UR226, Centre de recherche sur la Paléobiodiversité et les Paléoenvironnements (CR2P), Muséum national d'Histoire naturelle (MNHN)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS), Université des Antilles et de la Guyane (UAG)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-École Pratique des Hautes Études (EPHE), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Montpellier (UM)-Institut de recherche pour le développement [IRD] : UR226-Centre National de la Recherche Scientifique (CNRS)

Subjects
[SDV.BID.SPT] Life Sciences [q-bio]/Biodiversity/Systematics, Phylogenetics and taxonomy, [SDU.STU.PG] Sciences of the Universe [physics]/Earth Sciences/Paleontology, [SDU.STU.PG]Sciences of the Universe [physics]/Earth Sciences/Paleontology, [SDV.BID.SPT]Life Sciences [q-bio]/Biodiversity/Systematics, Phylogenetics and taxonomy, [ SDV.BID.SPT ] Life Sciences [q-bio]/Biodiversity/Systematics, Phylogenetics and taxonomy, ComputingMilieux_MISCELLANEOUS, [ SDU.STU.PG ] Sciences of the Universe [physics]/Earth Sciences/Paleontology
Abstract

International audience

Published
2014

17. An integrated palynological and paleontological study of the K-Pg Vilcapujio section, south-western Bolivia

Author

Pramparo, Mercedes B., Narvaez, P., Adnet, Sylvain, Andrade Flores, Ruben, Antoine, Pierre Olivier, Billet, Guillaume, Mamani Quispe, Bernardino, Marivaux, Laurent, Pujos, Francois, Instituto Argentino de Nivolog, Glaciolog y Ciencias Ambientales, Universidad Nacional de Colombia [Bogotà] (UNAL), Institut des Sciences de l'Evolution de Montpellier (UMR ISEM), École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Montpellier (UM)-Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Centre National de la Recherche Scientifique (CNRS)-Institut de recherche pour le développement [IRD] : UR226, Museo Nacional de Historia Natural, La Paz, Centre de recherche sur la Paléobiodiversité et les Paléoenvironnements (CR2P), Muséum national d'Histoire naturelle (MNHN)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS), Museo Nacional de Historia Natural La Paz, Universidad Nacional de Colombia [Bogotá], Institut des Sciences de l'Evolution de Montpellier ( ISEM ), Université de Montpellier ( UM ) -Institut de recherche pour le développement [IRD] : UR226-Centre National de la Recherche Scientifique ( CNRS ), Centre de recherche sur la Paléobiodiversité et les Paléoenvironnements ( CR2P ), Muséum National d'Histoire Naturelle ( MNHN ) -Université Pierre et Marie Curie - Paris 6 ( UPMC ) -Centre National de la Recherche Scientifique ( CNRS ), MARIVAUX, Laurent, Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-École Pratique des Hautes Études (EPHE), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Montpellier (UM)-Institut de recherche pour le développement [IRD] : UR226-Centre National de la Recherche Scientifique (CNRS)

Subjects
[ SDV.BV.BOT ] Life Sciences [q-bio]/Vegetal Biology/Botanics, [SDV.BV.BOT]Life Sciences [q-bio]/Vegetal Biology/Botanics, ComputingMilieux_MISCELLANEOUS, [SDV.BV.BOT] Life Sciences [q-bio]/Vegetal Biology/Botanics
Abstract

International audience

Published
2013

18. Depositional environments and hydrocarbon potential of the Middle Jurassic Los Molles Formation, Neuquén Basin, Argentina: palynofacies and organic geochemical data

Author

Martinez, Marcelo A., Pramparo, Mercedes B., Quattrocchio, Mirta E., and CARLOS ZAVALA

Subjects
Total organic carbon (TOC), Geochemistry and Petrology, Middle Jurassic, Stratigraphy, Neuquén Basin, Argentina, Paleontology, Geology, Palaeoenvironments, Hydrocarbon potential, Palynofacies
Abstract

Amultidisciplinary analysis of palynofacies in a sequence-stratigraphical framework, TOC (total organic carbon) and TAI (thermal alteration index) analyses, has been applied to outcrop samples of the uppermost Los Molles Formation (Middle Jurassic), Neuquén Basin, Argentina, in order to characterise the palaeoenvironmental and palaeo-climatic conditions during the deposition of this unit. Five types of palynofacies (P-l to P-5) have been identified and are interpreted to indicate a restricted marine to inner neritic environment. In P-1 and P-4, a marine environment close to the terrestrial source area with moderate oxidizing conditions and energy, is suggested. In P-2, the assemblage of freshwater algae, acritarchs and prasinophytes suggest a marginal marine environment influenced by fluvial discharge. In P-3, the marine microplankton content reflects conditions ranging from a marginal-marine (sub-normal salinity) to an inner neritic environment. In P-5, a dysoxic marine environment (probably marginal) is suggested. Warm and relatively humid (abundance of Cheirolepidiaceae in association withAraucariaceae) and locally humid (presence of swamps or ponds, on the alluvial plains) conditions are inferred. TOC content (65% of the analyzed samples reach TOC values over 1%), TAI values (2 to 2+, transitional between an immature phase and the window of liquid petroleum generation) and kerogen type (P-1, P-2 and P-5 show transitional characteristics between kerogen type II and III, while P-3 and P-4 show characteristics of kerogen type III and occasionally type IV), suggest that, in the studied area, the Los Molles Formation has some hydrocarbon potential. However, kerogen state suggests that the anoxic-dysoxic conditions of the site of deposition were not optimum for its preservation.

Published
2008

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