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Pennsylvanian glacimarine sedimentation in the Cushamen Formation,western North Patagonian Massif

Geoscience Frontiers 2018年第2期9卷 485-504页

作者： Paulo Marcos Daniel A.Gregori Leonardo Benedini Mercedes Barros Leonardo Strazzere Cecilia Pavón Pivetta Cátedra de Geofísica Departamento de GeologíaUniversidad Nacional del Sur and INGEOSURSan Juan 6708000 Bahía BlancaArgentina Cátedra de Geología Argentina Departamento de GeologíaUniversidad Nacional del Sur and INGEOSURSan Juan 6708000 Bahía BlancaArgentina Cátedra de Geología Minera Departamento de GeologíaUniversidad Nacional del Sur and INGEOSURSan Juan 6708000 Bahía BlancaArgentina

The metasedimentary sequence of the Cushamen Formation in the western North Patagonian Massif is540 m thick and comprises six sedimentary lithofacies associations related to a glacimarine *** of these lithofacies represent distal glacimarine environments, whereas another one was deposited in proximal glacimarine environments, and the last includes subglacial environments. The organization and configuration of these lithofacies associations represent the advance and retreat of the glacier masses. The maximum glacial advance is correlatable with the G2 glacial interval of the Pennsylvanian Pampa de Tepuel, Las Salinas and Valley Chico, formations of the Extraandean Chubut, and the southern part of Neuquen Cordillera. Contemporaneously, in southern Chile there are marine and glacimarine sediments. The chronostratigraphic relationships between the Silurian to Permian units allow five paleogeographic stages to be distinguished. The middle Silurian-late Devonian igneous rocks represent the first magmatic stage. The second stage, which is transitional to the first, is represented by a marine basin that includes the late Devonian-early Carboniferous Esquel and Rio Pescado formations and the Llanquihue Complex. The third stage(early-late Carboniferous) includes granitoids of the second magmatic event that partially overlapped the first magmatic igneous belt. The fourth stage belongs to the late Carboniferous sedimentation of the Cushamen and equivalent formations. The extended early Permian magmatism was the last Paleozoic event in the studied area.

关键词： Pennsylvanian Glacimarine sedimentation Cushamen Formation North Patagonian Massif

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High-frequency lacustrine sequence stratigraphy of clastic lakes:lessons from ancient successions

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Journal of Palaeogeography 2024年第4期13卷 621-645页

作者： Carlos Zavala Hua-Qing Liu Xiang-Bo Li Valentin Trobbiani Yang Li Mariano Arcuri Agustin Zorzano Departamento de Geología Universidad Nacional del Sur(UNS)Bahía BlancaBuenos AiresArgentina GCS Consulting Services Bahía Blanca Buenos AiresArgentina Research Institute of Petroleum Exploration&Development-Northwest PetroChinaLanzhou 730020China Consejo nacional de Investigaciones Científicas y Técnicas(CONICET) Buenos AiresArgentina Shandong University of Science and Technology Qingdao 266590Shandong ProvinceChina

Sequence stratigraphic concepts and methods provide novel tools for performing stratigraphic analysis,allowing us to improve our understanding of depositional models and basin *** controls and depositional elements(e.g.,surfaces,systems tracts,parasequences,etc.)recognized in conventional sequence stratigraphy are designed for marine-related *** contrast,the sequence stratigraphy of lacustrine successions is much more complex and poorly understood,because it is not driven by sea-level changes,but by a complex interaction between tectonics and high-frequency climatic *** comprehensive analysis of the water balance of lacustrine systems allows the recognition of three types of lake conditions:Underfilled,balanced-fill and overfilled *** the lake conditions in ancient successions is fundamental for unraveling lacustrine sequence stratigraphy,since these conditions effectively control water salinity,internal stacking pattern and the characteristics of systems *** lakes are hydrologically closed lakes,and consequently,the lake-level can highly fluctuate,driven by high-frequency wet-dry climatic *** wet periods,rivers supply water and sediments,resulting in fining-and thinning-upward elementary depositional sequences(EDS's)accumulated during the transgressive systems tract(TST).In contrast,dry periods are characterized by a relative lake-level fall with the subaerial exposure of lake margin areas during the regressive systems tract(RST).Lake water salinity can fluctuate from brackish to ***-fill lakes are partially closed lakes,and consequently,they have characteristics of both underfilled and overfilled *** the TST,the lake is in underfilled condition,and consequently,the introduction of water and sediment will accumulate a fining-upward interval until reaching the spill point during the maximum *** RST is accumulated under an overfilled lake condition,with coarseningupwa

关键词： Lacustrine sequence stratigraphy Underfilled lakes Balanced-fill lakes Overfilled lakes Forced transgression Forced regression

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Vegetation recovery after fire in mountain grasslands of Argentina

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Journal of Mountain Science 2020年第2期17卷 373-383页

作者： Alejandro LOYDI Flavia AFUNK Andrés GARCíA Renewable Natural Resources Center of the Semi-Arid Zone(CERZOS)–CONICET-UNS Bahia BiancaArgentina Department of Biology Biochemistry and PharmacySouth National UniversityBahfa BiancaArgentina Argentine Institute of Oceanography(IADO) CONICET-UNSBahia BlancaArgentina

Fire is a natural disturbance occurring every few years in many grasslands ecosystems. However, since European colonization, fire has been highly reduced or even suppressed in Argentinean grasslands, fostering ignitable material accumulation. This has led to occasional catastrophic controldemanding fire events, extended for larger areas. The aims of this work are to study vegetation recovery and change after a non-natural fire event in mountain grasslands. The study area is located in the Ventania mountain system, mid-eastern Argentina. We studied vegetation recovery after fire(January 2014) in two different communities: grass-steppes(grasslands) and shrub-steppes(open low shrublands). We measured vegetation cover, species richness and bare ground percentage in burned and unburned areas 1, 4, 8, 11 and 23 months after fire. Vegetation surveys were also performed at the end of the growing season(December) 11 and 23 months after fire. Data were analyzed using regression analysis, ANOVA and multivariate analysis(NMS, PERMANOVA). Both communities increased their vegetation cover at the same rate, without differences between burned and unburned areas after two years. Species richness was higher in shrublands and their recovery was alsofaster than in grasslands. Considering functional composition, besides transient changes during the first year after fire, there were no differences in abundance of different functional vegetation groups two years after fire. At the same time, shrublands showed no differences in species composition, while grasslands had a different species composition in burned and unburned plots. Also, burned grassland showed a higher species richness than unburned grassland. Data shown mountain vegetation in Pampas grassland is adapted to fire, recovering cover and richness rapidly after fire and thus reducing soil erosion risks. Vegetation in mountain Pampas seems to be well adapted to fire, but in grasslands species composition has changed due to fire.

关键词： Amelichloa caudata Forbs Grass Natural grassland Nassella trichotoma Piedmont valleys Shrubs Sierra de la Ventana Vegetation functional groups

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Early Permian arc-related volcanism and sedimentation at the western margin of Gondwana： Insight from the Choiyoi Group lower section

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Geoscience Frontiers 2016年第5期7卷 715-731页

作者： Leonardo Strazzere Daniel A.Gregori Leonardo Benedini CONICET and Catedra de Ceologia Argentina Departamento de Geologia Universidad Nacional del Sur San Juan 670 8000 Bahia Blanca Argentina

Permian sedimentary and basic to intermediate volcanic rocks assigned to the Conglomerado del Río Blanco and Portezuelo del Cenizo Formation, lower part of the Choiyoi Group, crop out between the Cordon del Plata, Cordillera Frontal and Precordillera of Mendoza Province, Argentina. The sedimentary rocks are represented by six lithofacies grouped in three facies associations. They were deposited by mantled and gravitational flows modified by high-energy fluvial currents that evolved to low-energy fluvial and lacustrine environments. They constitute the Conglomerado del Río Blanco, which cover unconformably marine Carboniferous sequences. Five volcanic and volcaniclastic facies make up the beginning of volcanic activity. The first volcanic event in the Portezuelo del Cenizo is basaltic to andesitic lava-flows emplaced in the flanks of volcanoes. Lava collapse produced thick block and ash *** in the intermediate volcanic rocks, there are dacites of different geochemical signature,which indicate that the development of acidic volcanism was coetaneous with the first volcanic *** geochemistry of these rocks induces to consider that the Choiyoi Group Lower section belongs to a magmatic arc on continental crust. The age of this section is assigned to the lower Permian（277 ？ 3.0Ma, Kungurian age）.

关键词： Choiyoi group lower section Conglomerado del Río Blanco Cordillera Frontal Argentina

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Dealing with a hyper-successful neighbor: effects of the invasive apple snail Pomacea canaliculata on exotic and native snails in South America

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Current Zoology 2019年第3期65卷 225-235页

作者： Mara A.MALDONADO Pablo R.MARTIN Laboratorio de Ecologia (DBByF) INBIOSUR (Universidad Nacional del Sur-CONICET) San Juan 670 Bahia Blanca(8000) Argentina

Pomacea canaliculata is a successful invader and also a competitor and predator of other snails and may play a key role in structuring freshwater snail communities both in its native and invaded range. In the present study we evaluated the contact and distant effects of P. canaliculata in its native range on exotic (Melanoides tuberculata and Physa acuta) and native snails (Heleobia parchappii, Biomphalaria peregrina, and Chilina parchappii). Habitat use was affected in P. acuta, H. parchappii, and B. peregrina by contact effects of P. canaliculata, whereas survival was only affected in P. acuta through combined con tact and dista nt effects. Fee undity was reduced in P. acuta and B. peregrina by combined con tact and distant effects;evidence of egg mass predation was also observed in both species. Melanoides tuberculata was not affected at all by P. canaliculata. The snail species with higher withdrawal resp on ses to con tacts with P. canaliculata were those that suffered less mortality by corporal contact, whereas snails with high crawling away responses suffered from higher mortality. The effects of P. canaliculata seem to be highly negative to small non operculate sn ails that lay gelati nous egg masses, whereas large operculate ovoviviparous snails are not affected in their survival and reproducti on. This apple snail may exert biotic resista nee agai nst P. acuta but could favor the establishme nt of M. tuberculata and other function ally similar species in new habitats in South America.

关键词： Ampullariidae behavior biotic resistance interspecific interactions

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deltas:a new classification expanding Bates's concepts

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Journal of Palaeogeography 2021年第3期10卷 341-355页

作者： Carlos Zavala Mariano Arcuri Mariano Di Meglio Agustin Zorzano German Otharan Ainara Irastorza Antonela Torresi Dpto.de Geologia Universidad Nacional del Sur(UNS)Bahia BlancaArgentina GCS Argentina SRL Molina Campos 1508000 Bahia BlancaArgentina Consejo nacional de Investigaciones Científicas y Tecnicas (CONICET)Buenos AiresArgentina

deltas constitute complex depositional systems formed when a land-derived gravity-flow(carrying water and sediments) discharges into a marine or lacustrine standing body of water. However, the complexity of deltaic sedimentary environments has been oversimplified by geoscientists over the years, considering just littoral deltas as the unique possible type of delta in natural systems. Nevertheless, a rational analysis suggests that deltas can be much more complex. In fact, the characteristics of deltaic deposits will depend on a complex interplay between the bulk density of the incoming flow and the salinity of the receiving water body. This paper explores the natural conditions of deltaic sedimentation according to different density contrasts. The rational analysis of deltaic systems allows to recognize three main fields for deltaic sedimentation, corresponding to(1) hypopycnal(2) homopycnal and(3) hyperpycnal delta settings. The hypopycnal delta field represents the situation when the bulk density of the incoming flow is lower than the density of the water in the basin. According to the salinity of the receiving water body, three different types of hypopycnal littoral deltas are recognized: hypersaline littoral deltas(HSLD), marine littoral deltas(MLD), and brackish littoral deltas(BLD). The basin salinity will determine the capacity of the delta for producing effective buoyant plumes, and consequently the characteristics and extension of prodelta *** littoral deltas(HOLD) form when the density of the incoming flow is roughly similar to the density of the water in the receiving basin. This situation is typical of clean bedload-dominated rivers entering freshwater lakes. delta front deposits are dominated by sediment avalanches. Typical fallout prodelta deposits are absent or poorly developed since no buoyant plumes are generated. Hyperpycnal deltas form when the bulk density of the incoming flow is higher than the density of the water in the receivi

关键词： deltas Hyperpycnal flows Homopycnal flows Hypopycnal flows Hyperpycnites Turbidites Sediment gravity flows Gravity flows

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Ultrastructure of multicellular dwarf males with external gametangium in Oedogonium macrandrium(Oedogoniales,Chlorophyta)

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BIOCELL 2013年第3期37卷 85-90页

作者： Silvana L.D’AMICO Patricia I.LEONARDI Eduardo J.CÁCERES Laboratorio de Ficología y Micología Departamento de BiologíaBioquímica y FarmaciaUniversidad Nacional del SurBahía BlancaArgentina CERZOS-CONICET Camino La Carrindanga Km 7Bahía BlancaArgentina

This is the first comprehensive ultrastructural study on dwarf males with external gametangia in the ge in the genus Oedogonium,from androspore germination to the liberation of mature male *** ultrastructure of the process in *** Wittrok is similar to that of Bulbochaete hiloensis(Nordstedt)Tiffany,butwith two remarkable *** ***:(1)instead of a true transverse wall,only condensed mucilage appears between the gametes of each antheridial cell,and (2)the cell wall between the basal cell and the basal most antheridial cell has simple plasmodesmata similar to those present in the transverse walls of vegetative cells,which are absent in ***.

关键词： androspores Chlorophyta dwarf males Oedogoniales Oedogonium macrandrium ultrastructure

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Seed bank dynamics of an invasive alien species, Helianthus annuus L.

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Journal of Plant Ecology 2020年第3期13卷 313-322页

作者： Alejandro Presotto Fernando Hernández Mauricio Casquero Roman Vercellino Claudio Pandolfo Mónica Poverene Miguel Cantamutto Dpto.Agronomía Universidad Nacional del Sur(UNS)San Andrés 8008000 Bahía BlancaArgentina CERZOS Universidad Nacional del Sur(UNS)-CONICETCamino La Carrindanga Km 78000 Bahía BlancaArgentina Corteva Agriscience.Integrated field Sciences RN N178 Km 112700 PergaminoArgentina Estación Experimental Agropecuaria Hilario Ascasubi Instituto Nacional de Tecnología Agropecuaria(INTA)RN N3 Km 7948142 Hilario AscasubiArgentina

Aims The ability to form persistent seed banks is one of the best predictors of species’potential to establish in new *** sunflower is native to North America where the formation of persistent seed banks is promoted by disturbance and it plays a key role on the establishment and persistence of native ***,the role of the seed banks on the establishment and persistence of invasive populations has not been ***,we evaluated the role of seed bank and disturbance on the establishment and fitness,and seed persistence in the soil in several sunflower biotypes collected in ruderal(wild Helianthus annuus)and agrestal(natural crop–wild hybrid)habitats of Argentina as well as volunteer populations(progeny of commercial cultivars).Methods In a seed-bank experiment,we evaluated emergence,survival to reproduction,survival of emerged seedlings,inflorescences per plant and per plot under disturbed and undisturbed conditions over 2 years;in a seed-burial experiment,we evaluated seed persistence in the soil over four springs(6,18,30 and 42 months).Important Findings Overall,seedling emergence was early in the growing season(during winter),and it was promoted by disturbance,especially in the first *** this,the number of inflorescences per plot was similar under both conditions,especially in *** the second year,emergence from the seed bank was much lower,but the survival rate was *** the seed-burial experiment,genetic differences were observed but seeds of ruderals and agrestals persisted up to 42 months while seeds of the volunteer did not persist longer than 6 *** agrestal biotype showed an intermediate behavior between ruderals and volunteers in both *** findings showed that wild and crop–wild sunflower can form persistent seed banks outside its native range and that disturbance may facilitate its establishment in new areas.

关键词： seed bank seed persistence wild sunflower invasive alien species ruderal agrestal

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Effects of absolute fasting on reproduction and survival of the invasive apple snail Pomacea canaliculata in its native range

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Current Zoology 2016年第4期62卷 369-375页

作者： Nicolas E. TAMBURI Pablo R. MARTIN INBIOsur (UNS-CONICET) Universidad Nacional del Sur Departamento de Biologla Bioquimica y Farmacia San Juan 670 8000 Bahia Blanca Argentina

A South American freshwater gastropod, the apple snail Pomacea canaliculata, has become a driver of ecosystemic changes in wetlands and an important rice pest after its introduction to various parts of the world, mainly Asia. The objective of this study was to study the effect of an abrupt interruption in food availability in the short term （up to 4 weeks） and long term （up to 8 months） on survival and re- productive activity. The main results indicate that short-term fasting mainly affects the survival of males, but only when they are raised together with females, probably due to a greater mate-searching activity that increases mortality in the individuals with lower reserves. The number of copulating snails or egg-laying females shows an abrupt drop when fasting and a rapid recovery after the food supply is restored. The strategy of discontinuing reproductive activity prioritizes energy conservation for the survival of the females. Interpopulation variation in resistance to starvation was observed in adults, which can be explained to some extent by the food availability that they experienced in their natural environment. No interpopulational differences in survival were seen in hatchlings. The mean maximum values of survival under starvation were 52.6 days in hatchlings and the 3.3% of adults survive over than 200 days, which may be a relevant trait in dispersal and establishment in new habitats.

关键词： absolute fasting reproduction invasive apple

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Grasslands Response to Livestock Grazing Intensity in the Austral Pampas(Argentina):Testing the Intermediate Disturbance Hypothesis

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Phyton-International Journal of Experimental Botany 2024年第8期93卷 2037-2050页

作者： Ana Elena de Villalobos María Andrea Long Grupo de Investigación en Ecosistemas de Pastizal(GIEP) CERZOSCONICETBahía Blanca8000Argentina Departamento de Biología Bioquímica y FarmaciaUniversidad Nacional del SurBahía Blanca8000Argentina

Livestock grazing has a significant impact on natural grasslands,with approximately one-third of the world’s land area dedicated to this *** 20%of global grasslands are highly degraded due to overgrazing,affecting their productivity and conservation *** practices are required to ensure sustainable livestock production that supports *** Intermediate Disturbance Hypothesis(IDH)suggests that environments with moderate levels of disturbance exhibit a higher species *** grazing can reduce the dominance of certain species,thereby enhancing plant ***,concerns arise regarding the increase of exotic and unpalatable species under moderate grazing levels,complicating grassland conservation *** impact of livestock grazing on the functional structure of grasslands depends on factors such as grazing intensity,livestock species,and environmental *** in grazing intensity may increase specific and functional diversity under moderate grazing,potentially masking the presence of invasive exotic *** the Austral Pampas(Pampean phytogeographic province,Buenos Aires,Argentina),grasslands face various pressures from domestic livestock grazing that endanger their integrity if not properly ***,our study aims to investigate potential differences in species richness and diversity,functional diversity,exotic plant abundance,and the number and distribution of plant functional groups across varying grazing *** IDH is utilized as a tool to regulate livestock pressure for grassland *** and functional diversity indices were used to assess the impact of grazing on grassland *** grazing increased species and functional diversity,while intensively grazed or ungrazed areas showed reduced *** presence influenced the balance between native and exotic plants,with ungrazed areas having higher native plant abundance and grazed areas exhibiti

关键词： Natural grasslands grazing effects disturbance specific and functional diversity

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