Neogene Micropaleontology and Stratigraphy of Argentina (introduction) (original) (raw)
Problems and concepts of paleopedology in Argentina
Quaternary International, 1998
Pedogenesis has played a major role in the evolution of the Pampean landscape which resulted in the common occurrence of pedogenic features in the stratigraphic successions, but has not been recognized in previous studies. The main problems facing paleopedological research are the identification of paleosol profiles, paleosol horizons and their interpretation. Paleosols have been traditionally interpreted as truncated profiles because A and E horizons were not recognized. This may be apparent or real. Erosion generally leaves supporting evidence such as a lag deposit, but superposed cycles of pedogenesis can obliterate original morphological properties, which alters the appearance of buried A and E horizons. Abrupt boundaries have always been interpreted as erosional surfaces because of an overgeneralization that all land surfaces are eroded. When paleosols are exposed in roadcuts and quarries, they acquire new morphological features such as induration and tension cracks, which have been misinterpreted as original properties. In the current view, the basic criteria for paleosol recognition in exposures are based on the vertical and lateral arrangements of soil morphological features within a detailed stratigraphic framework provided by sedimentary facies analysis. The framework can be verified by micromorphological studies of polygenetic horizons to determine the sequence of episodes of pedogenesis and to evaluate the effects of diagenesis following burial.
Palaeontology of the Cerros Bayos section, Roca Formation (Danian), La Pampa Province, Argentina
Alcheringa, 2007
del Río, C.J., Martínez, S.A., Stilwell, J.D. & Concheyro, A., September, 2007. Palaeontology of the Cerros Bayos section, Roca Formation (Danian), La Pampa Province, Argentina. Alcheringa 31, 241-269. ISSN 0311-5518.New mollusc and echinoid faunas are recorded from exposures of the Roca Formation at Cerros Bayos (La Pampa Province) and assigned to the Maastrichtian – Danian (CC26 – NP3 Zones of Martini 1971) on the basis of the associated nannofossil assemblages. The macroinvertebrate assemblages show increased diversity and abundance of molluscs from Zones NP1 to NP3. One new Danian echinoid, the spatangoid Bolbaster argentinensis sp. nov., is described. At least 19 molluscan genera are recognized; 14 of these, together with seven species, are identified for the first time from Danian exposures of La Pampa Province. An equivocal record of Pyropsis tumida Wilckens, 1905 may extend the range of this tudiclid gastropod from the latest Cretaceous into the Danian. The Cerros Bayos exposures substantially increase our knowledge of diversity trends and biotic recovery immediately following the Cretaceous – Paleogene boundary event, and provide clues to the composition of the little-studied earliest Paleogene faunas in southern Patagonia. Claudia J. del Río [cdelrio@macn.gov.ar], Museo Argentino de Ciencias Naturales B. Rivadavia, CONICET, A. Gallardo 470-C1405DJR Buenos Aires, Argentina; Sergio A. Martínez [smart@fcien.edu.uy], Instituto de Geología y Paleontología. Facultad de Ciencias, Iguá 4225, 11400 Montevideo, Uruguay; Jeffrey D. Stilwell [jeffrey.stilwell@sci.monash.edu.au], School of Geosciences, Monash University, Clayton VIC 3800, Australia; Andrea Concheyro [andrea@gl.fcen.uba.ar], Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pabellón II. 1428 Buenos Aires, CONICET and Instituto Antártico Argentino, Argentina; received 25.11.2005, revised 8.9.2006.
2009
s of the 9th International Conference on Fluvial Sedimentology Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 2 Acta geológica lilloana Serie publicada por la Fundación Miguel Lillo, que tiene como objetivo divulgar trabajos originales sobre ciencias geológicas y afines. Los trabajos son evaluados por árbitros externos e internos. Correo electrónico: actageologicalilloana@gmail.com I S S N 0 5 6 7 – 7 5 1 3 © 2009, Fundación Miguel Lillo. Todos los derechos reservados. Fundación Miguel Lillo Miguel Lillo 251 (4000) San Miguel de Tucumán Argentina Telefax +54 381 433 0868 www.lillo.org.ar Editora de Acta geológica lilloana: Ana Fogliata Secretaria editorial: Lucía Ibañez Secretaria del Área Geología: Rosa Molina Editor gráfico: Gustavo Sánchez Comité editorial: Dra. Ana S. Fogliata (Coordinadora) (Fundación Miguel Lillo, Facultad de Cs. Naturales, UNT) Dra. Lucía Ibañez (Secretaria) (Fundación Miguel Lillo, Facultad de Cs. Naturales, UNT) Dra. Jud...
The objective of this paper is to make a detailed and multiproxy geomorphological study of the middle section of Amaicha River in Northwest Argentina. The obtained evolutionary model and chronological context will be linked with previous models to include the study area in a regional context. Finally, our model will be used as a morphochronological base to contextualize the lithic materials found in an area which previously lacked stratified records and absolute datings. The geomorphological study shows the high dynamic of the sector recorded in the ravine deposits during the Holocene. This process is reflected by the aggradation/degradation stages. A basal unit chronologically assimilated to the Pleistocene (Pl unit) is overlapped by four Holocene morphosedi-mentary units (H1 to H4). These units are arranged as terraces following an alternating succession of aggradative and degradative phases. The interbedding of tephra layers of known age, as well as radiometrically dated peat levels and soils, enables a very complete chronology of the Holocene sequence to be made. Lithic artifacts were found in the s1 soil, dated to 5468-4875 cal BP, providing one of the few records of stratified archaeological sites in the region for those times. This paper constitutes an initial approach in the development of a regional evolutionary model covering the period from the Late Pleistocene until the present.
Advances in Geomorphology and Quaternary Studies in Argentina
Springer earth system sciences, 2017
The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publisher, the authors and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, express or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Advances in Geomorphology and Quaternary Studies in Argentina, 2019
The present contribution involves deposits of continental Neogene age that outcrop in the Bahía Blanca region. The studies that were carried out in order to contribute to the paleoenvironmental and chronostratigraphical knowledge involve sedimentological, paleomagnetic and magnetic susceptibility analyses. One of the outcrops studied (Cueva de Los Leones) is mainly composed of facies of fine to thick sandstones, largely pedogenized and with important amounts of calcrete, whereas the other (Loma Sarmiento) has a predominance of loess-like silt facies, reddish brown in colour, an abundance of rhizoconcretions and evidence of pedogenic processes. Both outcrops culminate in an important layer of calcrete of regional scope, with particular morphologies at each of the sites. The paleomagnetic analysis leads to the conclusion that the sedimentation of the deposits underlying the calcareous crust at the two sites was not synchronous. Reverse polarity was recorded in the Cueva de Los Leones in contrast to Loma Sarmiento, where normal polarity is predominant. The paleomagnetic samples of calcareous crust on the top presented anomalous polarity directions in both sections, with very high values of magnetic intensity. The reverse directions in the Cueva de Los Leones can be assigned to the Gilbert Cron (6.0-3.6 Ma), without discarding younger ages in the Pliocene. In contrast, Loma Sarmiento seems to be older (Late Miocene). The susceptibility records also indicated differences between the two sites that would be linked to pedogenic development; they were higher in Loma Sarmiento and judging by the F% factor, in Cueva de los Leones the superparamagnetic particles contribution is higher. Petrographic, X-Ray difractometry, paleontological and soil micromorphology analyses, in some places at the studied sites, also contributed to the paleoenvironmental/paleoclimatic reconstruction carried out.
western Argentinean basins: paleontological evidences
2016
The central western Argentinean basins of Río Blanco, Calingasta-Uspallata and western Paganzo, enclose the most complete marine successions used for examining the Carboniferous-Permian boundary in Gondwana. A detailed review of the key stratigraphical sections has allowed the identification of the latest Carboniferous assemblages; NBG, Interval megafloristic Zone and DM (Raistrickia densa-Convolutispora muriornata) Palynological Zone in the lower part, and the earliest Permian T-S (Tivertonia jachalensis-Streptorhynchus inaequiornatus) invertebrate Zone and FS (Pakhapites fusus-Vittatina subsaccata) Palynological Zone in the upper part. This diagnostic mega/microflora and marine invertebrate paleontological evidence provides a biostratigraphical framework for the definition of the Carboniferous-Permian boundary inside the basins of central western Argentina.
Journal of South American Earth Sciences, 1995
The Tunas Formation, extensively exposed in the Sierras Australes foldbelt of eastern central Argentina, completes the sedimentation of the Gondwanan (Late Carboniferous-Permian) sequence, locally known as the Pillahuincó Group. The underlying units of the Group show an integrated depositional history which can be explained in terms of glaciomarine sedimentation (Sauce Grande Formation) and postglacial transgression (Piedra Azul and Bonete Formations). This succession also has a rather uniform quartz-rich, sand-sized composition indicative of a cratonic provenance from the Tandilia Massif to the northeast.Early to Late Permian deformation folded and thrusted the southwestern basin margin (Sierras Australes) and triggered the deposition of a 1,500 m — thick, synorogenic prograding wedge, the Tunas Formation, in the adjacent foreland basin (Sauce Grande or Claromecó Basin). Sandstone detrital modes for the Tunas deposits show moderate to low contents of quartz and abundant lithics, mostly of volcanic and metasedimentary origin. Paleocurrents are consistently from the SW. Tuffs interbedded with sandstones in the upper half of Tunas Formation (Early — early Late? Permian) are interpreted as being derived from volcanic glass-rich tuffs settled in a body of water. Extensive rhyolitic ignimbrites and consanguineous airborne tuffaceous material erupted in the northern Patagonian region during that period. The age constraints and similarities in composition between these volcanics and the tuffaceous horizons present in the Sauce Grande, Parana and Karoo Basins suggest a genetic linkage between these two episodes. The intimate relationship between volcanic activity inboard of the paleo-Pacific margin, deformation in the adjacent orogenic belt and subsidence and sedimentation in the contiguous foreland basin constitutes a common motif in the Sauce Grande and Karoo Basins of southwestern Gondwana.El Grupo Pillahuincó (Carbonífero superior — Pérmico), ampliamente expuesto en las Sierras Australes de la provincia de Buenos Aires, está constituido, en orden estratigráfico ascendente, por las Formaciones Sauce Grande, Piedra Azul, Bonete y Tunas. Las primeras tres unidades comparten una proveniencia cratónica común derivada del Macizo de Tandilia ubicado hacia el NE y una evolución sedimentaria integrada por condiciones glaciamarinas (Formación Sauce Grande) seguidas por una transgresión representada por sedimentación de plataforma abierta (Formaciones Piedra Azul y Bonete).Para la Formación Tunas, por el contrario, se infieren áreas de proveniencia diferentes evidenciadas por paleocorrientes dominantes desde el SO y modas detríticas caracterizadas por contenidos moderados a bajos de cuarzo y abundantes fragmentos líticos, especialmente de origen volcánico. Estas caracteristicas se relacionan con deformación del tipo faja corrida y plegada que afectó el margen sudoccidental de la cuenca durante el Pérmico Temprano tardío y el Pérmico Tardío. Niveles tobáceos han sido identificados en la mitad superior de la unidad. Su espesor, el cual alcanza aproximadamente Ios 1500 m, y extensión areal (con afloramientos en la cuenca contigua de Sauce Grande o Claromecó) sugieren que los depósitos predominantemente arenosos de la Formación Tunas formaron parte de una cuña progradante hacia el NE. Debido a edades y rasgos composicionales similares, los niveles tobáceos pueden ser relacionados con las abundantes ignimbritas riolíticas presentes hacia el SO de las Sierras Australes en el Macizo Nordpatagónico e inclusive correlacionados con niveles tobáceos presentes en unidades contemporáneas de las cuencas de Paraná y Karoo. El carácter sinorogénico de la Formación Tunas queda además corroborado por la presencia de pliegues de crecimiento y metamorfismo contemporáneo detectado en unidades pre-carboníferas de las Sierras Australes.La relación íntima entre vulcanismo a lo largo del margen continental, deformación en la faja orogénica adyacente y sedimentación en las cuencas de antepaís contiguas constituye un rasgo común documentado en las Sierras Australes de Argentina y la zona del Cabo en Sudáfrica.
2009
A new fossil assemblage bearing graptolites, chitinozoans and acritarchs is analyzed based on material collected in the Pascha-Incamayo area, Salta Province, NW Argentina. The occurrence of Hunnegraptus copiosus (Lindholm, 1991), associated with specimens of the genus Tetragraptus (Salter, 1863), is highly relevant to improve the age assignment and correlate the fossil-bearing levels previously assigned to the Devendeus Formation. Different stages in the development of the index species of the Upper Tremadocian H. copiosus Biozone are described and illustrated. The precise stratigraphic ranges of the associated chitinozoans and acritarchs are discussed, according to the biostratigraphic analysis, and the stratigraphic relationships for the studied section are considered. © 2009 Académie des sciences. Published by Elsevier Masson SAS. All rights reserved.