Calcretes pedogenéticos da Bacia de Itaboraí, Estado do Rio de Janeiro

The Itaboraí Basin, located in Rio de Janeiro State, Brazil, is considered the first segment from the Southeastern Brazil Continental Rift opened, during the Paleocene. The occurrence of calcretes was previously reported in the literature, although studies dealing specifically with such calcretes and their distribution were not performed. Furthermore, there is limited research involving the petrographic characterization of the sedimentary deposits of the basin. This study developed a characterization on both macro and micro scale of the vadose calcretes that occur along the northern and western margins of the basin and constitute its initial infilling. The compositional, textural and fabric features of 27 thin sections prepared from calcrete samples were described and interpreted. The pedogenetic calcretes were separated in different facies (chalky, nodular, massive, platy, incipient laminar and brecciated), and classified according to morphogenetic stages. The main microscopic features include nodules, contraction cracks, vadose pisoliths, rhizocretions, infiltrated clays, corroded grains, expanded micas and clay aggregates. The pedogenetic calcretes were developed on weathered alluvial deposits during tectonic stability periods. They are typically generated on continental environments under arid to semiarid climates and occur intercalated with travertines (carbonate crusts of hydrothermal origin), which deposition is favored by fault activity during humid climate periods. The results indicate both pedogenetic and hydrothermal processes have been extremely active and have played important role during the early evolution of Itaboraí Basin. Thus, the characterization of such processes is essential to the understanding of the initial evolution of Southeastern Brazil Continental Rift.A Bacia de Itaboraí é considerada o primeiro segmento do Rifte Continental do Sudeste do Brasil a se abrir, durante o Paleoceno. Há referências à existência de calcretes na bacia, entretanto, até o momento, não foram realizados estudos específicos sobre os calcretes e sobre sua ocorrência, e ainda há um número reduzido de trabalhos envolvendo a caracterização petrográfica dos depósitos sedimentares da bacia. Apresenta-se aqui uma caracterização, macromorfológica e micromorfológica dos calcretes vadosos que constituem o preenchimento inicial da bacia e que são encontrados nas suas bordas norte e oeste. Foram descritos e interpretados os aspectos composicionais, texturais e de fábrica de 27 seções delgadas preparadas de amostras de calcretes. Os calcretes pedogenéticos mostram diferentes fácies (pulverulento, nodular, maciço, placoso, laminar incipiente e brechado), que foram atribuídas a estágios morfogenéticos distintos. As principais fei- ções micromorfológicas incluem: nódulos, gretas de contração, rizólitos, argilas infiltradas, grãos corroídos e fraturados, micas expandidas, e agregados argilosos. Os calcretes pedogenéticos se desenvolveram em depósitos aluviais intemperizados, em períodos de estabilidade tectônica e são característicos de ambientes continentais áridos a semiáridos. Ocorrem intercalados a travertinos, crostas carbonáticas de origem hidrotermal, cuja deposição é condicionada pela movimentação de falhas ativas e favorecida em períodos de clima úmido. Os resultados indicam que processos pedogenéticos e hidrotermais foram extremamente atuantes durante o início do preenchimento da Bacia de Itaboraí, e sua caracterização é importante para a compreensão da evolução inicial do Rift Continental do Sudeste do Brasil

Methodological Proposal for the Inventory and Assessment of Geomorphosites: An Integrated Approach focused on Territorial Management and Geoconservation

Geoconservation has been growing in importance within the environmental management context. The conservation of geological heritage is being more and more recognised as an essential issue in nature conservation. Inventories of geosites are considered basic steps in geoconservation strategies and constitute a tool to support management considering the sites’ values, use potential and risks of degradation. There are dozens of proposed methods to create inventories and to perform qualitative and quantitative evaluations of the sites and there are still discussions concerning the issues of how to select and evaluate sites and provide management guidelines. Geomorphosites are geosites with geomorphological nature and it is a category that presents some peculiarities highlighted in the literature. This work aimed at proposing a method for inventorying and assessing geomorphosites designed for territorial management focused on the use potential of the sites, divided into scientific, educational and geotouristic uses, the promotion conditions and the risks of degradation. The method was applied to the southeast coast of Rio de Janeiro State, Brazil, which has a high geomorphological diversity. The result was the creation of an inventory of geomorphosites in which all sites were described and quantitatively assessed, creating a product that can be easily applied in the management of the sites. The objective of this work was to contribute to the methodological discussions and to strengthen the insertion of geoconservation on territorial management

Community Perceptions for Geoconservation of a Coastal Area in Rio de Janeiro, Brazil

We collected socio-environmental data from the inhabitants of a coastal area in the State of Rio de Janeiro, Brazil, in order to investigate the local knowledge about environmental, economic and cultural particularities of the area and the main human activities that impact the environment. Community perceptions from 11 localities in the Região dos Lagos were evaluated. The data analysis can help in the development of specific geoconservation activities for the study area, which is located in the aspirant Geopark ‘Costões e Lagunas do Rio de Janeiro’. This initiative of considering community perceptions can help to maintain and protect local geological sites, raise public awareness of environmental matters and help to manage the development of the new Geopark. Furthermore, it can also contribute to the sustainable development of the area and to the planning of effective policies to sustain progress. Taking into consideration the answers and needs of the interviewed communities, the key topics requiring geoconservation activities in the study area are land use planning and biodiversity, urban mobility, continuous monitoring strategy, environmental awareness, wastewater, urbanisation, geotourism, sense of place, waste and economical activities.ISSN:1867-2477ISSN:1867-248

Targeting Sustainability Issues at Geosites: a Study in Região dos Lagos, Rio de Janeiro, Brazil

The aim of this study is to assess sustainability issues for a number of geosites in a study area of Região dos Lagos in the state of Rio de Janeiro, Brazil. The area within the proposed Geopark ‘Costões e Lagunas do Rio de Janeiro’ is well-known for its natural environment with unusual cliffs and hypersaline lagoons, some of them containing stromatolites. We have evaluated the changes in land use and land cover in this coastal area of Brazil over the last four decades and their relation to anthropogenic activities in the area. Land use change statistics indicate that the urban areas have increased to the detriment of the natural vegetation and salt pans. Local knowledge of sustainability issues were considered in order to identify the main threats to and protection needs of the geosites. The sustainability issues comprise environmental awareness, land-use planning and biodiversity protection. The geosite identified with the best sustainability is São Mateus Fort. The geosites found to be the most threatened are Brejo do Espinho, Peró Dunes, Lagoa Vermelha and Mangue de Pedra. Educational projects have been implemented in urban and rural areas of Região dos Lagos to teach the local population the importance of geosites and sustainable development.ISSN:1867-2477ISSN:1867-248

Community Perceptions for Geoconservation of a Coastal Area in Rio de Janeiro, Brazil

ISSN:1867-2477ISSN:1867-248