Geoquímica de sedimentos de fundo dos rios Trairí, Ararí e da Laguna Nísia Floresta (RN)

The metal concentrations (Al, Ba, Cd, Cr, Cu, Fe, Mn, Ni, Pb, Zn ) and phosforus(P) had been determined analyzed through Plasma Inductively Coupled Plasme Mass Spectrometer for fine fraction, < 0,63 mm in 22 samples. The sample preparation for analysis had been make in the laboratories of geology of the UFRN. This samples procedures consists in register, dry, bolt and send to analysis in external laboratory (LAKEFIELD GEOSOL) in Belo Horizonte (MG, Brazil). The studied area involves the rivers Trairi, Ararí and Nísia Floresta lagoon, that empties in the sea, situated in the Rio Grande do Norte State. The study objects (Rivers Trairí, Ararí and Nísia Floresta lagoon) receive influences from urban dumpies, agrotoxics and fertilizer, shrimps tank, pastoral, with this, the concentrations of metals (Al, Ba, Cd, Cr, Cu, Fe, Mn, Ni, Pb, P, Zn) (except phosforus) in some points of the study area had been above of the value of reference what it leads to classify them as not polluted to moderately polluted, as the calculated Igeo. In front of discussed, can say about the environmental problems found in Trairi, Ararí and Nísia Floresta Lagoon are still in small scale, since when regard the studied área is over human activity effects

Implicações tectônicas na hidrologia do aqüífero Barreiras e sistema lacustre do Bonfim, Nísia Floresta-RN

This MSc dissertation presents the results of a research carried out in a 500 km2 area in the Nísia Floresta county. The main goal of the research was to evaluate fault influence on hidrology features of aquifers and lakes, mainly in the Barreiras Group and in the Bonfim lake cluster respectively. The Precambrian crystalline basement is made of Caicó Complex rocks. They are capped by cretaceous sedimentary rocks and by cenozoic sedimentary rocks. Only the latter outcrop in the study area, wheareas the former are described in boreholes. Faults cut across all stratigraphic units and their main trends are NW, NE and E-W, which have been generated by E-W compression. Subordinate N-S trending faults also take place and have been generated by N-S oriented compression. Fault controlled hydrologic features are observed throughout the study area. There are sudden changes in saturated thicknesses of the Barreiras Aquifer due to vertical displacement of the Barreiras Group. The most important underground water source of the Bonfim Lake is related to abrupt thickness changes of the aquifer. In addition, the main faults control the underground drainage network and, probably, change in direction of equipotential surfaces seen on the potenciometric map. Regarding the surface hydrologic features, faults also control river and stream channels, as well as lake origin and shapes. The Bonfim Lake, in particular, has its peculiar shape, which follows NW and NE lineaments, and origin related to faulting and probably underground carstics processes

Aspectos Morfo-Dinâmicos daComplexo Lagunar Nísia Floresta-Papeba-Guaraíras, Região Costeira Sul Oriental Do RN

This dissertation presents the results of research developed in the Nísia Floresta-Papeba-Guaraíras Lagoon Complex, located on the south coast of the Rio Grande do Norte State. The main objectives of this dissertation were the stratrigraphic characterization, in detail scale, of the and the coastal dynamics study of the lagoonal deposits sedimentation, as well as the morpho-dynamic analysis of the area. Therefore, an interdisciplinary methodology was adopted, in which all sedimentological, morpho-tectonic and geomorphological data were integrated. Vibracore up to 4m in length were carried out in the lagoons. The referred lagoon complex made of a system of three lagoons that interact through two artificial channels, named Boqueirão and Surubajá. The Guaraíras lagoon, the largest one in the system, corresponds to the estuary zone of the Trairi and Jacu rivers. The sedimentary load brought by these rivers is strongly reworked by tide currents, forming an important net-work of channels and sandy bars inside this lagoon and close to its channel connection with the sea. The stratigraphic units of the area are Cenozoic in age, and are represented by sedimentary rocks of the Barreiras Formation (sandstones, mudstones and conglomerates) and by rocks beach, as well as by siliciclastics sediments related with the fluvial dynamics of tide plain (clay and sandy bars), and coast (sand dunes and beaches). Among the recognized geomorphologic aspects, there are the elements associated with continental enviroments (drainage basins of the Trairi, Baldum and Jacu rivers, coastal tableland supported by the Barreiras Formation), and transitional environments (lagoon complex, dune fields, cliffs, tidal channels and beach rocks lines). The morphotectonic analysis indicates that fauts affect Barreiras Formation sedimentary rocks, with two sets of main lineaments: SW-NE and SE-NW. The anomalies in the drainage net are directly associated with these fault/fracture system, which control and subdivede the low courses of the Trairi and Jacu rivers, at least a tail of their flowing principal courses. The Nísia Floresta, Papeba and Guaraíras lagoons present strong morphological control according to the lineament directions. Taking into account the lagoonal deposits, the sedimentological analyses reflect a sediment distribution related to the interaction of the fluvial and sea processes that act in the study area. The correlated deposits show textural mainly microclastic characteristics of shallow waters, and of currents of low to moderate energy.In general, the Nísia Floresta-Papeba-Guaraíras lagoon Complex, constitutes a very intrinsec group, that undewent important changes in historical times that are reflected in the currents clays. Inaddition to the natural processes that act in this system, we should take into account the antrohopic intervention, which have increased in the past years

Mapeamento da zona costeria protegida por arenitos de praia (Beachrocks) em Nísia Floresta - RN

The goal of this work comprises the detailed mapping of the coastal zone of the south coast of the State of Rio Grande do Norte. The emphasis of the study is the units of beachrocks and the features of the physical environment associated. The mapping of the beachrocks and of the adjacent coastal features is justified, among other aspects, by the fact that the beachrocks constitute an important protection agent against the sea erosion. By one side, they dissipate the energy of the sea waves and make possible the imprisonment of sediments in the foreshore. The beachrocks in the studied area are constituted of discontinuous strips, parallel to the coast line presenting emerged in some places, even in the highest tides, entirely submerged or partially buried by coastal sediments. These sandstones compose the landscape of big part of the coast and they are responsible for the partial dissipation of the energy of the waves on the studied coast. The methodology used in this work consisted of different techniques were used, as the use of aerial pictures of small format (FAPEFs), acquisition of data of system of global positioning (GPS) and later elaboration of thematic maps and of digital models of soil (MDTs). The results obtained in the mapping of the use and occupation of the soil, demonstrate the existence of strong human pressure in the coastal area (built lots and no built), occupying about 54,74% of built areas. This problem has been taking to degradation risks due to the inconsequent expansion of divisions into lots and tourist enterprises. The MDT came as an excellent resource, as visual as functional, being possible to visualize several angles and to act in three dimensions the relief of the area in study, as well as to identify the present features in the coastal area. By the importance of the bodies of beachrocks as a protection agent against the coastal erosion, faces were delimited in the sandstones based in geometric criteria, classifying them in, central face, outside face, inside face, break and undermiming. These last two associates to the erosion and washout in the base of these bodies. Field data indicate clearly that the most important process in the fracturing of the bodies is associated with mechanisms related to the gravity, being the joints formed by processes of gravitational sliding. Finally, the mapping of the coastal zone starting from aerial pictures of small format it made possible the identification of the elements that compose the beach strip, for accomplishing with larger detailed level and by presenting a better monitoring of the dynamics of the coastal zone