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La Formación Guandacol en su localidad homónima es conocida por los extensos depósitos de la glaciación gondwánica. Sin embargo ésta área también es importante debido a la excelente exposición de Depósitos de Transporte en Masa (MTD) que debido a sus características y dimensiones, son ejemplos a escala sísmica en el mundo. La gran cantidad de sedimento acumulado rápidamente en una cuenca subsidente, favorecieron al desarrollo de estos depósitos, expuestos debido a la inversión tectónica a lo largo de la falla de Valle Fértil. Este trabajo documenta uno de los ejemplos más completo de una sucesión de MTD´s, desde la cicatriz de deslizamiento hasta el desarrollo de estos depósitos, con todos sus elementos sedimentarios y deformacionales característicos. Se describen tres intervalos de MTD´s: el MTD 1 aflora en los Cerros Bola y guandacol, donde en ésta última área algunos autores sugieren una discontinuidad separando la sección basal en una nueva formación. El MTD 2, de 200 m de espesor, presenta una exposición continua de 10 km en el Co Bola y 4 km en el Co Guandacol. El MTD 3 es más complejo ya que presenta fallas sinsedimentarias, que permiten el desarrollo de conglomerados de ?post-rilling? a lo largo de la superficie de la cicatriz de deslizamiento. Los tres MTDs son perfectamente correlacionables en ambos afloramientos, donde también se muestra cómo cambian facialmente desde un margen hacia el centro de cuenca. Estas sucesiones son ejemplares únicos, ya que una secuencia así, solo ha sido observada en registros sísmicos a la fecha. This paper reports and analyzes the presence of large, seismic-scale, mass transport deposits (MTDs) recorded within the Guandacol Formation. These major submarine landslides seem to be connected with the occurrence of glacial episodes. The Guandacol Formation is part of the Paganzo Basin fill of Norwest Argentina (Fig. 1), and it is well known for recording several glacial cycles of the Late Paleozoic Ice Age. In this contribution we report and describe three major glacial/deglacial cycles (Fig. 1b) of Mississippian/Pennsylvanian age (Valdez et al., 2013). Outcrops of Guandacol Formation in Cerro Bola and Sierra de Maz (Cerro Guandacol) areas preserve those glacial cycles and each consists in the succession from non-glacial deltaic deposits to proglacial and thick mass-transport deposits (resedimented diamictites), which are the aim of this study, and finally postglacial marine varied strata, including sandy turbidites, shales with and without dropstones and some deltaic deposits (Milana et al., 2010; Dykstra et al., 2011). This study focuses on Sierra de Maz and Cerro Bola localities because they show very well exposed seismic-scale MTDs that otherwise would be quite difficult to see (Fig. 2a, b). Thus, these outcrops give the opportunity to compare many characteristics that are usually seen in seismic records, directly on the ground. On this sense, this contribution is mainly oriented to describe the facial and geometrical interrelations between these large MTDs (as there are many minor MTDs) and not the detailed internal architecture or their comparison to specific seismic features. The occurrence of these large MTDs can be explained by the large amounts of sediment delivered to the basin triggered by glacial- deglacial episodes. Due to the scarcity of well-exposed mega-scale MTD successions, a detailed study is being carried out since a few years. The result of detailed mapping of this rough terrain allow an excellent correlation between single MTDs, for several kilometers from Guandacol to Bola Hill outcrops (Fig. 3), and also portraying how a single MTD changes laterally when passing from a basin-margin environment (Guandacol Hill) to a basin-center environment (Bola Hill). The local Guandacol Formation shows three large glacial cycles that are mainly represented by single large MTDs and/or MTD composite intervals. The oldest MTD1 crops out completely in the Guandacol Hill, but only the upper part is present at Bola Hill (Fig. 4). MTD1 particular diagenesis and broad folds caused some authors to separate it from the Guandacol Formation, but we did not find any significant unconformity other than the normal upper relief between it and the following inter-MTD deposits. MTD2 is the largest and occurs as basin widens and more accommodation space is available. Reaching up to 200 m thick, it crops out continuously for more than 10 km in Bola Hill and 4 km in Guandacol Hill (Figs. 5, 6). The MTD3 is more complex due to its encroaching with large syn-sedimentary faults that we interpret as a large-scale slide scar associated to the MTD3 interval (Figs. 9, 10). This potential slide scar is associated with other elements as incised valleys or rilling at the scar surface, which have been observed in subsurface examples. Therefore one of the largest example of MTD successions and probably the best exposed worldwide is documented for the first time as a large, seismic-scale slide-scar cropping out in association to an MTD interval, with all the suite of sedimentary and deformational elements that might be expected for this play. Due to the fact these features are rarely exposed altogether, we expect this outcrop could be a world-class example to observe features cropping out that otherwise could be only studied indirectly from deep-water seismic surveys. This succession also serves as an example of how some sedimentary features could be easily mistaken by tectonic features when the scale of the sedimentary processes involves the discrete movement of large volumes (several km3) of semiconsolidated sedimentary units, as in the case presented here. Fil: Buso, Victoria Valdez . Universidade do Vale do Rio Dos Sinos; Brasil Fil: Milana, Juan Pablo. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Fisicas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico San Juan. Centro de Investigaciones de la Geosfera y Biosfera; Argentina Fil: Kneller, Benjamin. University Of Aberdeen; Reino Unido

Molards are conical shaped, often-symmetrical, debris mounds with a distinctive radial grain-size gradation, which were first-named in the Alps over 100 years ago. Historically these features did not receive much academic attention as they were rarely observed. Today, six different interpretations can be applied to molards, and the most recent has suggested a link to permafrost failure. The aim of this research was to test the hypothesis that molards result from the failure of permafrost-bearing ground and subsequent melting of the frozen debris boulders. This hypothesis is tested here by: 1) reviewing the known global distribution of molard-bearing mass movements with respect to permafrost distribution; 2) investigating a landslide in the Andes of Argentina with unequivocal relation to permafrost failure, 3) the survey and interpretation of the external and internal structure of molards, applying sedimentary transport concepts and 4) reproducing molards by laboratory simulation. Results show that, with few exceptions, molards are produced from the melt-out from the ice of permafrost blocks. In particular, a permafrost source of the mass flow is more certain for molard densely populated landslide deposits. This study serves to reappraise the presence of molards as they could be used to track permafrost degradation on mountainous areas and hence climate changes (temperature or precipitation). Fil: Milana, Juan Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico San Juan. Centro de Investigaciones de la Geosfera y Biosfera; Argentina. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Fisicas y Naturales; Argentina

We thank de Silva (2010) for the opportunity to discuss the origin of the unique megaripples(MR) found on the Puna Plateau. Forman and Kröhling were invited as co-authors of this Reply,because we produced new data supplied here. De Silva suggests that the genetic relationship inferred by Milana (2009) between MR and bedrock topography is in error. The next four topics may encompass de Silva´s concerns. 1) Age of MR. 2) Structure. 3) De Silva also questioned the creep of 2–3-cm-sized volcanic clasts. 4) While creep action is not in debate, its linkage to MR final shape should be. The lack of correspondence between grain size and MR size does not accomplish the modified ballistic hypothesis. On the other hand, shape and size of MR seem controlled by topography as shown by Milana (2009, his figure 3), suggesting that wind flow structure controls, to some extent, large MR formation. However, this is hypothetical and will remain so until instrumental data can be acquired. In conclusion, we do not find any disagreement with data supplied by de Silva and the genetic relation between MR and bedrock topography. Thus, the most likely explanation for this type of bedrock erosion is the still unknown interplay between wind fl ow structure and a granular bed. Fil: Milana, Juan Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Forman, Steven. University of Illinois; Estados Unidos Fil: Krohling, Daniela Mariel Ines. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Se presentan los primeros registros paleontológicos de la Formación Lagarcito (Albiano) provenientes de la sección La Yesera Sur, sobre la ladera oriental de la sierra de Guayaguas, en el sudeste de la provincia de San Juan, en el centro-oeste de Argentina. Varios episodios lacustres se detectaron a lo largo del perfil, pero sólo en tres de ellos el contenido paleontológico y palinológico resultó abundante. Se describen e ilustran ocho especies de algas clorofíceas, tres de conchóstracos y once de ostrácodos no marinos. La asociación es indicadora de un ambiente lacustre somero, con buena disponibilidad de nutrientes en una primera etapa y alta evaporación, demostrado por la presencia de yeso interestratificado hacia la parte superior de cada episodio lacustre. Dos especies de conchóstracos son descriptas como nuevas: Dendrostracus lagarcitoensis Gallego sp. nov. y Pseudestherites rivarolai Gallego sp. nov., The first paleontological records from the Lagarcito Formation (Albian) in the eastern side of the sierra de Guayaguas (La Yesera Sur section), south-eastern San Juan Province, central-western Argentina, are presented. Although several lake episodes have been detected, only three of them have yielded abundant palynologic and paleontologic remains. Eight chlorophyte algal species, three conchostracan species and eleven non-marine ostracod species, are described and illustrated. The associations indicate a shallow lacustrine environment, that was initially rich in nutrients and with high levels of evaporation, as demonstrated by interstratified gypsum towards the top of each lacustrine episode. Two of the conchostracan species described are new: Dendrostracus lagarcitoensis Gallego sp. nov. and Pseudestherites rivarolai Gallego sp. nov., Facultad de Ciencias Naturales y Museo