Estudo da barreira IV na região do Cassino, Rio Grande, RS : evolução e caracterização como reservatório

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Indicative value of non-pollen palynomorphs (NPPs) and palynofacies for palaeoreconstructions: Holocene Peat, Brazil

The results of the palynological study of the samples from the core, performed in the Aguas Claras peatland, RS, Brazil (50°45′00″W, 30°00′15″S), focus on detailed taxonomic analysis of non-pollen palynomorphs (NPPs) and palynofacies from the Holocene peat and underline the Late Pleistocene mud and sandy mud that were represented. NPPs from the samples revealed taxonomic variety of fungal palynomorphs, presented by Brachysporium, Clastesporium, Dicellaesporites, Dicellaeporisporites, Gelasinospora, Glomus, Sordaria, Helicoon, and others. The habitats of above mentioned taxa are varied: aquatic, mycorrhizal, parasitic, organic matter decaying, and dung-coprophilous. Freshwater algal palynomorphs were composed of Botryococcus, Closterium, Debarya, Mougeotia, Pseudoschizaea, Spirogyra, and Zygnema. The percentage ratio between algal and fungal palynomorphs was changed from the different samples of the core, reflecting climatic oscillations (more humid-dryer). Prevalence of fungal palynomorphs was connected with dryer climate, and on the contrary, freshwater algal palynomorph predominance was related with increasing humidity. The six palynomorph zones that corresponded to the six principal phases of environmental and climatic changes were determined. The zone from the uppermost part of peat was characterized by relatively frequent dungcoprophilous and parasitic fungi, as a result of agricultural and domestic activities. Palynofacies analysis combined to NPPs was used for palaeoenvironmental and paleoclimatic reconstructions. Palynofacies from the samples were characterized by evident changes in relationship (%) between the different types of organic matter, their quality, and quantity and fluorescence index. The obtained data contribute to the understanding of the peat deposition. The combined use of NPPs and palynofacies analyses provided a valuable approach for the paleoenvironmental and paleoclimatic reconstructions

Copper bioavailability and fractionation in Copper-contaminated sandy soils in the wet subtropics (southern Brazil)

We studied the distribution, bioavailability and speciation of copper in subtropical sandy soils exposed to long-term applications of copper-based fungicide. In the surface horizon of the contaminated soils, bioavailable copper surpasses the toxic threshold for plants up to several times. Mobile fractions of copper predominate in top layers, contributing to contamination spreading downward to groundwater. Copper accumulates on the underlying iron hydroxide barrier in quantities comparable to total copper concentrations in the surface horizon. Despite the impediment of the geochemical barrier, most applied copper reaches the aquifer, contaminating the groundwater

Diversidade Polínica de Plantas em Dunas no Extremo Sul do Brasil

Neste trabalho são apresentadas a composição taxonômica das palntas em dunas e as microfotografias dos polens correspondentes e pertencentes as 43 espécies de 22 famílias de plantas vasculares, e uma espécie de uma família de pteridófitos. Esse trabalho é a primeira apresentação da variabilidade de polens de plantas de dunas atuais, nativas e invasoras no extremo sul na planície costeira do Rio Grande do Sul. Os resultados obtidos foram catalogados e armazenados na forma de uma palinoteca, e poderão facilitar futuras identificações de polens fósseis encontrados nos sedimentos quaternários e auxiliar nas reconstruções paleográficas, que incluam ambientes correlatos à cobertura vegetal de dunas costeiras.The taxonomic composition of the dune plants and pollen microphotographs of correspondent 43 species vascular plants of 22 families and one species of ferns are repredented in this paper. This paper is the first presentation of pollen variability of the extant native and introduced plants of dune, distributed in the extreme south of the coastal plain of the Rio Grande do Sul State. The obtained results based on palynoteka will facilitate inidentifications of fossil pollen concluded in the Quaternary sediments and help in palaeogeographic reconstructions, including the past history of vegetation cover of dunes in this region

Holocene paleoinlet of the Bojuru region, southern Brazil

The Holocene environmental evolution of the Bojuru region, Rio Grande do Sul state, southern Brazil, was inferred from seismic, geochronologic, sedimentologic, and paleontologic data. The absolute ages of two samples, determined by the 14 C method, are 9400+-140 Cal BP and 7370+-150 Cal BP. On the basis of lithology and palynomorph and diatom data, the six stages of paleoenvironmental development of this region were chosen. Layers of muddy sediments characterized by a significant incidence of marine palynomorphs and marine and estuarine diatoms were deposited during the Early and Middle Holocene. Seismic records (3.5 kHz) revealed a prominent buried paleochannel that can be correlated to the present Barra Falsa channel. The main period of the channel incision was related to the last regressive event of the Late Pleistocene. During the last Holocene transgression, this paleochannel was filled up by fluvial, estuarine, and marine sediments. The integrated analysis of data reveals that the Barra Falsa feature resulted from a former channel connecting the Patos lagoon and the Atlantic Ocean. The closure of this inlet channel is attributed to shifts in the sedimentation milieu related to the transgressive maximum and subsequent regression during the Late Holocene.A evolução ambiental holocênica da região de Bojuru, estado do Rio Grande do Sul, Brasil, é aqui reconstruída tendo como base novos dados paleontológicos, sedimentológicos, sísmicos e de datação radiométrica do carbono. Duas amostras foram datadas por 14C, fornecendo idades absolutas de 7370 ±150 e 9400 ±140 anos AP. Dados litológicos, palinológicos e de diatomáceas permitiram o reconhecimento de seis etapas paleoambientais para a região, relacionadas com oscilações do nível do mar e mudanças climáticas. Camadas de argila e lama, caracterizadas pela presença significativa de palinomórfos marinhos e de diatomáceas marinhas e estuarinas, foram depositadas durante o aumento do nível do mar correspondente á última transgressão marinha. Dados sísmicos de 3,5 kHz revelam a existência de um grande paleocanal correlacionável ao canal atual da Barra Falsa. O período principal de formação do canal é relacionado ao último evento regressivo do final do Pleistoceno. No decorrer do último grande evento transgressivo o canal foi sendo progressivamente preenchido por sedimentos fluviais, estuarinos e marinhos. A análise integrada dos dados indica que o canal da Barra Falsa é uma herança morfológica de um antigo canal que conectava a laguna dos Patos ao oceano aberto. O fechamento deste canal é atribuído as mudanças nas condições ambientais ocorridas durante o máximo transgressivo e subseqüente regressão do final do Holoceno.Fil: Weschenfelder, Jair. Universidade Federal do Rio Grande do Sul; BrasilFil: Medeanic, Svetlana. Universidade Federal do Rio Grande do Sul; BrasilFil: Corrêa, Iran C. S.. Universidade Federal do Rio Grande do Sul; BrasilFil: Aliotta, Salvador. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Argentino de Oceanografía. Universidad Nacional del Sur. Instituto Argentino de Oceanografía; Argentin

Os palinomorfos nas reconstruções paleoambientais: Azolla filiculoides Lam. Nos sedimentos holocênicos da planície costeira do Rio Grande do Sul

Com base no estudo de 11 amostras de lama do fundo da laguna dos Patos, palinomorfos variáveis representados por poles e esporos de plantas terrestres e aquáticas vasculares, zigósporos, coenobium e colônias de clorofilas, cistos de dinoflagelados e de acritarcas, e palinomorfos de fungos foram registrados. As assembléias de palinomorfos são de origem alóctone e se diferenciam pela diversidade taxônomica e frequência de taxa, vinculadas com as características ecológicas da laguna, a vegetação terrestre e aquática, nas áreas adjacentes à laguna, influência do oceano e proximidade da bacia de drenagem. Os palinomorfos de algas são mais abundantes na parte sul da laguna(pré- límnica), mas são mais diversos pelos taxa na parte norte(límnica). A maior diversidade de polens e esporos ocorre nas amostras de áreas sob a influência do Rio Camaquã e do Lago Guaíba. A frequência maior de polens de plantas de dunas e de marismas ocorre na parte leste. Os diversos fitólitos são relativamente frequentes nas amostras de locais próximos as dunas e marismas.Based on 11 muddy samples of bottom sediments from the Patos Lagoon, various palynomorphs represented by pollen, and spores of terrestrial and aquatic vascular plants , zygospores, coenobias and colonies of Chlorophyta, cysts of dinoflagellates and acritarchs and fungal palynomorphs were registered. The palynomorph assemblages are allochtonous by origin and are differed by taxonomic diversity and frequency of taxons which are connected with ecological characteristic of the Lagoon , terrestrial and aquatic vegetation in adjacent to lagoon areas, ocean influence, and proximity to drainage basin. The algal palynomorphs are more abundant in the southern part of the Lagoon(pre-limnic), but are more diverse by taxons in the northern part(limnic). The most pollen-and-spore diversity is encoutered in the samples from the points subjected by River Camaquã and Lago Guaíba influence. In the east, there are more pollen of dune and intertidal marsh plants. Diverse phytoliths are relative abundant from the samples in the points of sampling not far from the dune and intertidal marshes

Os fitólitos em gramíneas de dunas do extremo sul do Brasil: variabilidade morfológica e importância nas reconstruções paleoambientais costeiras

Os fitólitos produzidos pelas monocotiledôneas e preservados nos sedimentos quaternários, nas planícies costeiras, são ferramentas importantes nas reconstruções paleoambientais. Atualmente, a aplicação dos fitólitos em estudos do Quaternário das áreas costeiras do Brasil ainda não foi elaborada. A implicação convincente dos fitólitos poderá ser feita com base em coleção de referência dos fitólitos de plantas atuais. Neste trabalho, são apresentadas as descrições morfológicas dos fitólitos de sete espécies de gramíneas atuais, as quais são amplamente distribuídas nas dunas, no extremo sul da planície costeira do Rio Grande do Sul (RS), Brasil. Os resultados mostram a grande variedade dos fitólitos de gramíneas, e as suas características morfológicas e específicas para cada espécie. As características mais próximas dos fitólitos, entre si, foram observadas nas espécies pertencentes às subfamílias de Panicoideae, Pooideae e de Chloridoideae. Alguns fitólitos dispersos encontrados nos sedimentos foram identificados com base em comparações com os fitólitos descritos em plantas de gramíneas, e outros ainda não foram identificados. A frequência relativa dos fitólitos nos sedimentos de ambientes diferentes ao relato de palinomorfos mostra que os fitólitos possuem uma capacidade limitada de transporte para longas distâncias. Foram registrados abundantemente em turfeiras holocênicas onde eles se depositaram “in situ” após a decomposição das plantas-mães.The phytoliths, produced bby monocotiledonous plants and preserved in the Quaternary sediments in the coastal plains are important indicators for palaeoenvironmental reconstructions. Present day, the using of phytoliths for the Quaternary studies in the coastal areas in Brazil has not been elaborated yet. The persuasive implications of phytoliths will be made on the base of reference collection of phytoliths obtained from extant plants. In this work, the morphological descriptions of phytoliths in seven species of ramineous plants, wide spread in dunes of the extreme south coastal plain of Rio Grande do Sul State (RS), Brazil are represented. The results show a great variety of phytoliths in gramineous plants whose morphological characteristic are resembled between specie in subfamilies of Panicoideae, Pooideae, and Chloridoideae. Some dispersed phytoliths which were encountered in sediments were identified basing in comparison with the described phytoliths, and others have not been identified yet. The approximate relative frequencies of phytoliths in the different sediments may indicate on their limited capacity to transport for the long distance. The most abundant and diverse phytoliths were registered in the Holocene peat where they were probably deposited “in situ” after parent plant decomposition

Notas sobre Fitólitos em Androtrichum trigynum (Spr.)Pfeiffer no Extremo suldo Brasil: Tipos morfológicos e uso nas paleoreconstruções costeiras

A convincente identificação dos fitólitos dispersos nos sedimentos quaternários poderá ser feita com base em uma coleção de referência de fitólitos obtidos de plantas atuais da mesma família. Neste trabalho foram descritos os fitólitos produzidos por Androtrichum trigynum, ciperácea psamófila, endêmica nas regiões de dunas e inter dunas das planícies costeiras do sul da América do Sul. Os principais morfotipos de fitólitos para essa espécie são: (1) alongados irregularmente e ondulados, (2) de contornos irregulares ondulados (Lobulisaxum), (3) com formad de trapézios sinuosos curtos soltos ou articulados, e (4) arredondados. Os fitólitos lobados são extremamente raros. Alguns fitólitos encontrados nos sedimentos holocênicos lagunares da planície costeira do Rio Grande do Sul foram comparados com os fitólitos descritos para Androtrichum trigynum. As descrições dos fitólitos são acompanhadas de ilustrações.Convincing recognition of dispersed in the quaternary sediments phytoliths could be made using reference collection of phytoliths from the parent extant plants. In this work, phytoliths produced by one psammophylous species of sedge Androtrichum trigynum, an endemic species, in dunes and interdunes in the coastal plains of the South America, were described. The main morphological types of phytoliths for this species are: (1) elongate irregularly waved, (2) contours wavy irregular (Lobulisaxum). (3) single or articulated short wavy trapeziums, and (4) rounded. Lobate phytoliths are extremely rare. Some phytoliths, encountered in the Holocene lagoon sediments in the coastal plain of the Rio Grande do Sul State werw compared with the phytoliths defined from Androtrichum trigynum. The descriptions of phytoliths are accompanied by illustrations

Estudo da barreira IV na região do Cassino, Rio Grande, RS : evolução e caracterização como reservatório

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Characterization and environmental interpretation of a floodplain Holocene paleosoil: Implications for paleohydrological reconstructions in the Upper Paraná River, Brazil

Alluvial paleosoil horizons from the 3 to 4 m high banks of the Paraná River were used to reconstruct the palaeoenvironmental history and palaeohydrological regime of the river. The bank consists of a Middle to Late Holocene sequence of sandy to silty clay layers of overbank deposits. The paleosoil horizon is located to a depth of 1.95 m from the top of the bank and is recognized as a guide horizon throughout the floodplain of the Upper Paraná River floodplain. Analyses of organic matter (δ13C and humic/fulvic acids), palynology (pollen and charcoal fragments), magnetic susceptibility, micromorphology, x-ray diffraction and 14C dating were conducted for samples from two representative profiles of the study area. Two phases were characterized in the history of the river: 1) An older phase, of stability in fluvial hydrology (stasis) with low frequency of floods, which produced conditions for soil development (14C 1700 ± 70 yr. BP). At this period, the predominance of herbaceous vegetation (determinated by pollen and δ13C analyses) suggests a climate less humid than the present one, and 2) A second phase, when climate changed to the present conditions of humidity (annual rain fall of 1600 rum) and characterized by the predominance of C3 plants. Under this new hydrological regime, the river developed an agradational floodplain, with a depositional sedimentary rate of 1.2 mm.y-1. © 2006 Gebrüder Borntraeger