Abstract Stromatolites are laminated biosedimentary structures of great importance for paleobiological, paleoecological, and paleoenvironmental analyses, mainly in Precambrian rocks. Their value is related to the glimpse of past life recorded in their lamination, fabric, and, eventually, due to the preservation of organic matter, including microfossils, and because their deposition is directly influenced by environmental conditions. Although stromatolites are widely described in microscopic scale, there is a lack of standardization of their nomenclature, precluding better paleoenvironmental and paleobiological interpretations. In this study, we propose a guide for the microscopic analysis of fossil stromatolites and, possibly, thrombolites, and provide a review of specialized literature and the bibliometric context of main terms. The goal is to contribute to the improvement of their application through systematization of microscopic data, in the face of novel paleoecological and paleobiological approaches and for astrobiological prospection for microbialites in therock record of Mars. analyses rocks lamination fabric eventually matter microfossils conditions scale nomenclature interpretations study possibly thrombolites terms data Mars

Abstract Microbialites are the most abundant life evidence in Precambrian sedimentary rocks. They are produced by microbial interaction activity and sedimentary processes reflecting paleoenvironmental conditions. The Ediacaran-Cambrian carbonate and siliciclastic successions in the Southern Amazon Craton in Central Brazil, provide a key opportunity to understand how the metazoan life coexisted with the microbial communities. The spatial and temporal distribution of microbialites as well as morphological and paleoenvironmental changes have been assessed, reinterpreting previous works and including new data from the Araras-Alto Paraguai and Corumbá basins. The deposition was controlled by subsidence and sea-level changes that affected these basins, considered extensions of epicontinental seas during the Gondwana assembly. The stromatolites are restricted to coastal deposits and experienced thriving flourishment intervals after the Marinoan Glaciation (635 Ma). Post-glacial transgression was marked by microbial colonization in shallow platforms represented by stratiform and giant domical stromatolites in the Araras-Alto Paraguai Basin. The continuity of the transgression generated a moderately deep aragonite sea at about 622 Ma. A progressive sea-level fall caused the implantation of coastal environments under greenhouse conditions with tidal flat and sabkha settings colonized by centimetric-scale stromatolites. The sea retreat was accompanied by progressive uplift, causing a moderate inversion of the basin and erosion of the succession until ~560 Ma with the deposition of the last preserved tidal flat deposits with the occurrence of thrombolites. The subsiding Corumbá Basin was the site of microbially-induced deposition of carbonates in a shallow platform connected to an offshore setting with the proliferation of metazoan straddling the Ediacaran-Cambrian boundary. Microbial communities were restricted to lagoon deposits during the Lower Cambrian transgression in the Araras-Alto Paraguai Basin and the last phase refers to the sea retreat towards southeast, developing a fluvial system connected with the arid and evaporitic tidal flats colonized by microbialites that lasted until the upper Cambrian. Except for the post-glacial stromatolites, the columnar and domal microbialite indicate that the coastal settings dominated the Ediacaran-Cambrian transition. The preservation of microbialites in the post-glacial intervals can be associated with the Mg-Ca-CO3 oversaturation in dolomitic platforms. The rapid calcification and ability to resist the dissolution and replacement have increased the stromatolites’ preservation potential reported here, where its well-preserved occurrence in tidal flats and sabkha occurs due to intense early diagenetic silicification. The change from carbonate accumulation to siliciclastic-rich environments contributed to the demise of microbially-induced strata. In general, the scarce coexistence between coastal stromatolite and metazoan-bearing marine deposits makes it challenging to establish a competitive relationship between these organisms, as previously postulated.

Abstract The appearance of complex megascopic multicellular eukaryotes in the Ediacaran occurred just when the dynamics of a cooling Earth allowed establishment of a new style of global tectonics that continues to the present as “modern-type plate tectonics”. The advent of this style was first registered in 620 Ma-old coesite-bearing Ultra-High Pressure eclogites within the Transbrasiliano-Kandi mega-shear zone along the site of the West Gondwana Orogeny (WGO). These eclogites comprise the oldest evidence of slab-pull deep subduction capable of inducing continental collisions and producing high-relief Himalayan-type mega-mountains. Life, prior to this time, was essentially microscopic. Yet with increasing Neoproterozoic oxygenation and intensified influx of nutrients to Ediacaran oceans, resulting from the erosion of these mountains, complex macroscopic heterotrophic eukaryotes arose and diversified, taking the biosphere to a new evolutionary threshold. The repeated elevation of Himalayan-type mega-mountains ever since then has continued to play a fundamental role in nutrient supply and biosphere evolution. Other authors have alluded to the influence of Gondwana mountain-building upon Ediacaran evolution, however we claim here to have identified when and where it began.

RESUMO Apresentamos resultados parciais de um projeto de pesquisa em que vimos discutindo o papel da escrita na formação de professores. A premissa geral é a de que escrever sobre a aula pode ser um trabalho pelo qual o professor produz, para si e para outros, dados que permitem levar adiante, por meio de uma atividade posterior, a reflexão e os posicionamentos assumidos por ele no próprio momento da aula. Neste artigo, focamos a exposição de dois aspectos dessa pesquisa: a análise de tipo "polifônico", centrada no deslindamento das "vozes" que compõem o discurso escrito sobre a aula, baseada nas ideias de O. Ducrot; e o questionamento sobre o que a configuração do enunciado pode dizer acerca do "sujeito empírico" responsável por ele, afastando-nos de Ducrot em favor de Bakhtin. Os dados discutidos aqui representam dois universos: textos escritos por estudantes cursando disciplinas de prática em cursos de Letras e artigos acadêmicos sobre o ensino de língua publicados em periódicos da área. Apontamos três problemas comuns a ambas as esferas: a) o uso de termos "vicários" em substituição ao registro de informações concretas; b) a inserção de discursos citados como enunciados a que se responde e não como dados que se analisam; c) conclusões sobre o ensino que não se vinculam aos dados ou análises apresentadas. Sintetizamos os resultados das análises afirmando que, quando se trata de discutir o que se passa na sala de aula, mesmo quando se escutam as "vozes" que emanam desse espaço, não se lhes confere um estatuto claro de dado, dando-se aos discursos citados tratamentos diversos e fazendo com que o discurso resultante seja inconsistente enquanto análise da aula.

ABSTRACT We present partial results of a research project in which we discuss the function of writing in teachers' education. The general premise is that writing about a class may be an activity through which the teacher produces, to himself and to others, data that will allow him to keep working on the ideas and positions assumed by him when in class. In this paper we focus on two aspects of this research: the "polyphonic" analysis centered on unfurling the "voices" that make up a written discourse about the class, based on the ideas of O. Ducrot; and the questioning of what the configuration of the enunciate may show about the "empirical subject" responsible for it, diverging from Ducrot in favor of M. Bakhtin's ideas. Our data comprise two universes: texts written by Language Arts students during their in-school training and papers on the teaching of Portuguese published in academic journals. We point out three problems that are common to both kinds of data: a) the use of "weasel words" in the place of concrete information; b) the insertion of cited discourses as enunciates to which one answers instead of as data that one analyses; c) conclusions about the class that do not result from the data analysis that is shown. We synthesize our results by stating that, when it comes to discussing what goes on in the classroom, even though one might listen to the "voices" that come from there, such voices hardly receive any treatment as data and are responded to in different ways; the resulting discourse is thus inconsistent as far as an analysis of the class.

Neste artigo defendo que um dos entraves centrais do ensino de Português é a dificuldade de o professor sustentar um discurso específico sobre o seu objeto de especialidade, o que põe em jogo sua própria condição profissional. Contra isso, venho pesquisando a formação de um "discurso profissional docente" através da análise da escrita de alunos de graduação em Letras. Apresento aqui a leitura de um relatório de estágio a partir do conceito de "imagem" proposto por Pêcheux (1969). Problematizo especificamente alguns processos de escrita que parecem favorecer a evasão do sujeito em relação à sua experiência mais do que a construção de conhecimento a partir dela. Nesse caso, em vez de se valer de instrumentos teóricos para analisar dados empíricos, o sujeito adere a explicações laterais ao seu objeto de análise, cujo motor é a ocultação de uma imagem de si. O resultado é uma elaboração que dificilmente se traduz em efeitos de formação, mas antes preserva o caráter leigo de seu discurso sobre o ensino.

In this paper we defend that one of the main drawbacks in Portuguese first language teaching in Brazil is the teachers' difficulty to sustain a specific discourse about their object of expertise, which in turn puts their professional status at stake. In order to revert this, we have been studying how a "professional teacher's discourse" comes into being by analyzing pieces written by undergraduate students in Languages and Literature. We present here an analysis of an internship report based on the concept of "image" such as proposed by Pêcheux (1969). We discuss particularly writing procedures that favor the subject's evading her own experience more than using it to build new knowledge. In this case, instead of using theoretical instruments, the subject clings to explanations that stand beside her object of analysis, moved by the need to conceal an image she sustains of herself as a teacher. The result is a construction that can hardly push towards any educational improvement, but rather preserves the layman character of her discourse.

Contra a ideia de que os conhecimentos técnicos do professor de língua materna sirvam prioritariamente ao conteúdo de seu ensino ou ao planejamento de suas aulas, neste artigo, discute-se o preceito de que tal conhecimento seja assumido também como base para a elaboração de uma atitude a ser mantida nas interações face a face da sala de aula. Essa atitude diz respeito à constante necessidade de tomar decisões diante do inesperado e aponta para a construção de um lugar discursivo específico do professor de língua - o de quem escuta a palavra do aluno e a enlaça à sua, de maneira a garantir que a assunção de um lugar de sujeito passe por uma reflexão sobre os meios linguísticos disponíveis para tanto. Toma-se como exemplo para esse debate a interpretação inusitada que alguns alunos fazem da palavra "rataria", presente num texto de Monteiro Lobato. Discutem-se certas atitudes que poderiam ser tomadas em relação a esse erro de leitura e suas implicações: requisitar a modificação da resposta, modificar o material didático, explicitar o trabalho linguístico subjacente ao erro ou utilizar o erro como pretexto para outras atividades. Os encaminhamentos discutidos fundamentam-se na premissa de que erros e outras manifestações imprevistas não apenas revelam procedimentos de construção do conhecimento, mas também oferecem oportunidades importantes para que o professor se faça incluir na palavra do aluno, sendo, portanto, um aspecto fundamental na construção de uma relação em que o ensino se torne possível.

Contrary to the idea that the technical knowledge of the teacher of a native tongue serves primordially to the content of its teaching or to the planning of classes, this article discusses the precept that such knowledge should be seen as the basis for the creation of an attitude to be maintained in face-to-face interactions in the classroom. This attitude relates to the constant need to make decisions before the unexpected, and points to the construction of a specific discursive place for the language teacher - that of someone who listens to the student's words and enlaces them to his or her own words, so as to make sure that the assumption of the position of subject follows a reflection about the linguistic means available to such end. As an example to fuel this debate, the text describes the case of the unusual interpretation made by some students of the word "rataria" present in one of Monteiro Lobato's works. Some of the possible attitudes before this reading mistake are discussed, as well as their implications: to request a change in the answer, to modify the didactic material, to make explicit the linguistic work underlying the mistake, or to use the mistake as a pretext to other activities. The procedures discussed are based on the premise that mistakes and other unforeseen manifestations not only reveal procedures of construction of knowledge, but also offer important opportunities for the teacher to include him/herself into the student's word, being, therefore, a fundamental aspect in the construction of a relationship in which teaching becomes possible.