Significado deposicional e diagenético de argilominerais na transição Ediacarano-Cambriano : formações Tamengo e Guaicurus (Grupo Corumbá, MS)

Dissertação (mestrado)—Universidade de Brasília, Instituto de Geociências, Programa de Pós-Graduação em Geologia, 2018.As formações Tamengo e Guaicurus, unidades superiores do Grupo Corumbá, estão posicionadas na transição Ediacarano-Cambriano devido a dados bioestratigráficos e quimioestratigráficos. A Formação Tamengo é composta majoritariamente por calcários com intercalações pelíticas e registra ocorrência de macro-fósseis do gênero Cloudina e Corumbella, enquanto a Formação Guaicurus é caracterizada como um extenso e homogêneo pacote de siltitos. Essa pesquisa tem como foco a caracterização sedimentar, petrográfica, mineral (Difratometria de Raios-X) e química (Fluorescência de Raios-X) de pelitos e siltitos com objetivo de definir posicionamento estratigráfico das formações Tamengo e Guaicurus, além de indicar ambiente deposicional e história diagenética das mesmas. Para tal, foram estudadas três áreas na região de Corumbá (MS-Brasil): pedreiras Laginha e Corcal e afloramento ao longo da MS-243. As rochas da Formação Tamengo, sob microscópio, apresentam feições de difusão de fluidos, laminações irregulares, lâminas de calcita como pseudomorfos de evaporitos e esteiras biogênicas. Em contraste, os siltitos da Formação Guaicurus são persistentemente laminados, bem selecionados e homogêneos. Ambos os pelitos intercalados em camadas carbonáticas e os siltitos são compostos por quartzo e mica detríticos e argilominerais diagenéticos. Ainda, composições químicas de óxidos maiores são amplamente similares, com exceção do conteúdo de Na2O, maior nos siltitos da Formação Guaicurus. A presença de rochas carbonáticas intercaladas com pelitos na Formação Tamengo implica ambiente favorável à formação de carbonatos com aporte episódico de material siliciclástico imaturo, proveniente de rochas de granulação muito fina de uma área-fonte próxima, interrompendo deposição de carbonatos. A Formação Guaicurus, distintamente, é um resultado de um aporte ininterrupto de material siliciclástico imaturo de uma área-fonte próxima, amplamente similar à Formação Tamengo, e depositado sob baixa energia com lâmina d’água espessa, abaixo do nível de base de ondas de tempo bom. A paragênese de argilominerais diagenéticos – illita, clorita e quartzo – e os valores de índice de Kübler caracterizam estágio de anquizona a diagênese tardia para ambas as formações. Todavia, a Formação Tamengo apresenta grande quantidade de esmectita, característica de diagênese precoce, além de feições petrográficas indicativas de evento de circulação de fluidos. Essas evidências revelam história diagenética complexa com ocorrência de retrodiagênese para os pelitos da Formação Tamengo. Os siltitos da Formação Guaicurus não apresentam evidências petrográficas de difusão de fluidos nem presença de esmectita na paragênese illita + clorita, confinando esse evento de circulação de fluidos na Formação Tamengo. Após caracterização, esta pesquisa ainda revelou que a porção superior da pedreira Corcal (L7) expõe rochas da Formação TamengoConselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq).The Tamengo and Guaicurus formations, upper units of the Corumbá Group, are placed at Ediacaran-Cambrian transition due to biostratigraphy and chemostratigraphy data. The Tamengo Formation is composed mainly of limestones with mudstones interbedding and record occurrences of macro-fossils Cloudina and Corumbella. The Guaicurus Formation is characterized as an extensive and homogeneous siltstone package. This paper focus in sedimentary, petrographic, mineral (X-Ray Diffraction) and chemical (X-Ray Fluorescence) characterizations of mudstones and siltstones in order to define stratigraphic positioning of the Tamengo and Guaicurus formations, to indicate depositional environment and diagenetic history. To this porpoise, three areas were studied in the vicinity of Corumbá (MS-Brazil): Laginha and Corcal quarries and an outcrop along MS-243 road. The rocks of Tamengo Formation, under microscope, present fluid diffusion features, irregular laminations, calcite laminas as evaporate pseudomorphes and biogenic mats. In contrast, siltstones of Guaicurus Formation are persistently laminated, well sorted and homogenous. Both mudstones interbedded in carbonate layers and siltstones are composed of detrital quartz, mica and diagenetic clay minerals. Furthermore, the major oxides compositions are broadly similar, except for Na2O, higher in the Guaicurus Formation. The presence of carbonate rocks and mudstones within Tamengo Formation imply environment favorable to carbonate formation with episodically immature siliciclastic supply, from very fine-grained rocks of a nearby area, interrupting carbonate depositions. The Guaicurus Formation, distinctively, is a result of an uninterrupted immature siliciclastic supply from a nearby source area, broadly similar to the Tamengo Formation, and was deposited under a low energy setting in a high water level, below fairweather wave. Diagenetic clay mineral paragenesis – illite + chlorite + quartz – and Kübler indexes characterize anquizone to late diagenesis stage for both formations. However, the Tamengo Formation presents great amounts of smectite, characteristic of early diagenesis stage, along with petrographic features indicative of a fluid circulation event. These evidences reveal a complex diagenetic history with retrograde diagenesis recorded in the mudstones of the Tamengo Formation. The siltstones of the Guaicurus Formation present neither petrographic evidences of fluid diffusion nor presence of smectite along the paragenesis illite + chlorite, constraining the fluid circulation event in the Tamengo Formation. After these characterizations, the research revealed that the superior portion of Corcal quarry (L7) exposes rocks from the Tamengo Formation

New facies model and carbon isotope stratigraphy for an ediacaran carbonate platform from South America (Tamengo Formation—Corumbá Group, SW Brazil)

The Ediacaran is a period characterized by the diversification of early animals and extensive neritic carbonate deposits. These deposits are still not well understood in terms of facies and carbon isotope composition (δ13C). In this study we focus on the Tamengo Formation, in southwestern Brazil, which constitutes one of the most continuous and well-preserved sedimentary record of the late Ediacaran in South America. We present new detailed lithofacies and stable isotopes data from two representative sections (Corcal and Laginha) and revise the paleoenvironmental and stratigraphic interpretation of the Tamengo Formation. The Corcal section consists of neritic deposits including shallow-water limestone beds, alternated with shale and subordinate marl beds. These facies yield specimens of the Ediacaran fossils Cloudina lucianoi and Corumbella werneri. On the other hand, the Laginha section shows more heterogeneous facies, such as impure carbonates, breccias, marls, and subordinate mudstone beds, as well as no evidence of Corumbella werneri. The stable carbon isotope record is also different between the two sections, despite belonging to the same unit. The Corcal section displays higher and more homogeneous δ13C values, consistent with those of Ediacaran successions worldwide. The Laginha section, instead, displays more variable δ13C values, which suggest the influence of local and post depositional processes. The difference between the two sections was attributed to the different distance from the shore. We propose that the difference is due to topographic variations of the continental platform, which, at the Laginha site, was steeper and controlled by extensional faults. Therefore, the Corcal section is a better reference for the Tamengo Formation, whereas the Laginha is more particular and influenced by local factors. Besides, the lithofacies associations of the Tamengo Formation are like those of the Doushantuo and Dengying formatios, in South China, with no significant biogenic carbonate buildups, and different from those of other important Ediacaran units, such as the Nama Group in Nmibia and the Buah Formation in Oman. Our work highlights the complexity and heterogeneity of Ediacaran carbonate platforms and of their carbon isotopic composition. In addition, we characterize the Corcal section as a possible reference for the Ediacaran in South America

How future surgery will benefit from SARS-COV-2-related measures: a SPIGC survey conveying the perspective of Italian surgeons

COVID-19 negatively affected surgical activity, but the potential benefits resulting from adopted measures remain unclear. The aim of this study was to evaluate the change in surgical activity and potential benefit from COVID-19 measures in perspective of Italian surgeons on behalf of SPIGC. A nationwide online survey on surgical practice before, during, and after COVID-19 pandemic was conducted in March-April 2022 (NCT:05323851). Effects of COVID-19 hospital-related measures on surgical patients' management and personal professional development across surgical specialties were explored. Data on demographics, pre-operative/peri-operative/post-operative management, and professional development were collected. Outcomes were matched with the corresponding volume. Four hundred and seventy-three respondents were included in final analysis across 14 surgical specialties. Since SARS-CoV-2 pandemic, application of telematic consultations (4.1% vs. 21.6%; p < 0.0001) and diagnostic evaluations (16.4% vs. 42.2%; p < 0.0001) increased. Elective surgical activities significantly reduced and surgeons opted more frequently for conservative management with a possible indication for elective (26.3% vs. 35.7%; p < 0.0001) or urgent (20.4% vs. 38.5%; p < 0.0001) surgery. All new COVID-related measures are perceived to be maintained in the future. Surgeons' personal education online increased from 12.6% (pre-COVID) to 86.6% (post-COVID; p < 0.0001). Online educational activities are considered a beneficial effect from COVID pandemic (56.4%). COVID-19 had a great impact on surgical specialties, with significant reduction of operation volume. However, some forced changes turned out to be benefits. Isolation measures pushed the use of telemedicine and telemetric devices for outpatient practice and favored communication for educational purposes and surgeon-patient/family communication. From the Italian surgeons' perspective, COVID-related measures will continue to influence future surgical clinical practice

Global disparities in surgeons’ workloads, academic engagement and rest periods: the on-calL shIft fOr geNEral SurgeonS (LIONESS) study

: The workload of general surgeons is multifaceted, encompassing not only surgical procedures but also a myriad of other responsibilities. From April to May 2023, we conducted a CHERRIES-compliant internet-based survey analyzing clinical practice, academic engagement, and post-on-call rest. The questionnaire featured six sections with 35 questions. Statistical analysis used Chi-square tests, ANOVA, and logistic regression (SPSS® v. 28). The survey received a total of 1.046 responses (65.4%). Over 78.0% of responders came from Europe, 65.1% came from a general surgery unit; 92.8% of European and 87.5% of North American respondents were involved in research, compared to 71.7% in Africa. Europe led in publishing research studies (6.6 ± 8.6 yearly). Teaching involvement was high in North America (100%) and Africa (91.7%). Surgeons reported an average of 6.7 ± 4.9 on-call shifts per month, with European and North American surgeons experiencing 6.5 ± 4.9 and 7.8 ± 4.1 on-calls monthly, respectively. African surgeons had the highest on-call frequency (8.7 ± 6.1). Post-on-call, only 35.1% of respondents received a day off. Europeans were most likely (40%) to have a day off, while African surgeons were least likely (6.7%). On the adjusted multivariable analysis HDI (Human Development Index) (aOR 1.993) hospital capacity > 400 beds (aOR 2.423), working in a specialty surgery unit (aOR 2.087), and making the on-call in-house (aOR 5.446), significantly predicted the likelihood of having a day off after an on-call shift. Our study revealed critical insights into the disparities in workload, access to research, and professional opportunities for surgeons across different continents, underscored by the HDI

Alternative nursery propagation for vineyards establishment

Dead vines are often a problem present in many vineyards and are due to physiological or pathological causes whereby the vines need to be replaced. The aim of the trial was to create in the nursery plant material of four cultivars in order to easily replace the dead vines in the vineyards but also to anticipate the first harvest and to improve the vineyard uniformity and synchronize the vineyard management practices during the first two years of plantation. During the first year in the nursery, the effect of plant density on the percentage of success and vegetative growth was evaluated. During the second year, in the open field and only for one cultivar, the vegetative and reproductive parameters were evaluated in vines with or without bunches. Results in the nursery showed that the row spacing did not affect nursery success. Only the cultivars showed significant effects. Instead, plant density influenced the stock and shoot diameters that were increased by the widest in-row spacing. Results in the field showed that bunch removal affected shoot elongation, daily shoot growth, stem diameter, pruning mass and root mass. Yield was strongly related with the nursery shoot diameter. Crop load affected root mass

Il paesaggio antico in Molise nell’area del cratere: nuovi dati dai recenti scavi della Soprintendenza

Polo Museale del Molise; SABAP-Mol, Giornata di Studi “Il paesaggio antico tra passato, presente e futuro”, Campobasso Palazzo Iapoce 14 marzo 2017: Il paesaggio antico in Molise nell’area del cratere: nuovi dati dai recenti scavi della Soprintendenz