José Antonio Ferrari

Insolation-driven changes in atmospheric circulation over the past 116,000 years in subtropical Brazil

During the last glacial period, large millennial-scale temperature oscillations—the ‘Dansgaard/Oeschger’ cycles—were the primary climate signal in Northern Hemisphere climate archives from the high latitudes to the tropics. But whether the influence of these abrupt climate changes extended to the tropical and subtropical Southern Hemisphere, where changes in insolation are thought to be the main direct forcing of climate, has remained unclear. Here we present a high-resolution oxygen isotope record of a U/Th-dated stalagmite from subtropical southern Brazil, covering the past 116,200 years. The oxygen isotope signature varies with shifts in the source region and amount of rainfall in the area, and hence records changes in atmospheric circulation and convective intensity over South America. We find that these variations in rainfall source and amount are primarily driven by summer solar radiation, which is controlled by the Earths precessional cycle. The Dansgaard/Oeschger cycles can be detected in our record and therefore we confirm that they also affect the tropical hydrological cycle, but that in southern subtropical Brazil, millennial-scale climate changes are not as dominant as they are in the Northern Hemisphere.

Caracterização morfométrica de uma superfície cárstica do Vale do Ribeira, São Paulo (Núcleo Caboclos - Petar)

A method to obtain morphometric parameters of karst surfaces is proposed based on GIS techniques. An example of application is presented resulting in a quantitative signature of the total carbonatic surface area as well as in an individual characterization analysis of closed depressions. The following parameters were calculated: roughness, slope, topographic amplitudes, drainage density and circularity of closed depressions. Spatial and correlation analysis of the main parameters were done. The results show that more circular depressions are characterized by smaller areas and little drainage development. Larger depressions present lower circularity and possess well developed drainage networks and a higher topographic range. Based on the spatial distribution of the parameters and on the circularity values, the planimetric form of the depressions is interpreted as a result ofanisotropy of the resistance of bedrock to drainage development.

Identificação das áreas de recarga de fontes cársticas com o uso do traçador rodamina FWT , área carbonática Lajeado - Bombas, Iporanga, São Paulo

Qualitative tracing tests with rhodamine FWT dye were employed to identify the structure of underground drainage and to define recharge areas of karst springs in a limestone plateau located in the rain forests of southeastern Brazil. A method is proposed for the interpretation of qualitative tests based on natural background fluorescence obtained with charcoal detectors. The results of connection tests between sinkholes and springs showed that at least three karst conduit networks are responsible for plateau drainage: one of convergent structure (Areias), one of divergent structure (Corrego Fundo) and one whose structure has not yet been determined (Bombas). The results show that the detection of hydrologic connections with rhodamine FWT and activated charcoal is viable in the karst landscapes located in rain forests of southeast Brazil.

O carste no plano de manejo do Parque Estadual Intervales e zona de amortecimento, Estado de São Paulo, Brasil

Located in the valleys of the Ribeira de Iguape and Paranapanema Rivers, where karst features and a large number of caves can be found, the Intervales State Park and its buffer zone lie within an area of Proterozoic carbonate rocks that are of great interest to the mining industry. Based on geomorphological and geological studies, the characterization of the karst was performed in order to develop a management plan for the Intervales State Park and its buffer zone. With this, it was possible to defi ne the degree of vulnerability of the karst aquifer to contamination. The areas of greatest vulnerability are those that facilitate injection of contaminants directly into the aquifer, being characterized by such karst features as caves and sinks. In regions where recharge occurs exclusively via diffuse infi ltration, and runoff convergence with surface watercourses, the degree of vulnerability is lower. Considering this analysis, areas with the greatest impact potential were identifi ed and recommendations made regarding management of the park and its buffer zone.

Comportamento hidrodinâmico de sistemas cársticos na bacia do rio Betari, Município de Iporanga - SP

Time series analyses of spring hydrographs and pluviometric data are applied in order to characterize the groundwater flow in a karst aquifer of a highland plateau in the Upper Ribeira Valley (Alto Vale do Ribeira). Two kinds of karst spring behavior were revealed based on their contrasting statistical characteristics: one is extremely inertial (the Lago spring) while the other (the Areias spring) has a fast response to rainfall events, returning quickly to the pre-impulse stage. The differences are explained on the basis of system geometry together with flow dynamics (investigated by qualitative and quantitative fluorescent dye tracer tests), by recharge volume and mechanisms (identified through the mapping of catchment areas and surface karst features) and conceptual models which relate spring flow and discharge characteristics with the internal structure of the groundwater drainage. The spring with inertial behavior is part of a distributive drainage system, and the meteoric recharge is made by small catchment basins. On the other hand, the Areias spring corresponds to a convergent drainage system (which is observed along the Areais cave system) with meteoric recharge characterized by large inputs at discrete points connected to the largest allogenic recharge areas.

Análise comparativa da extração automatizada de dolinas a partir de modelos digitais de terreno

Topographic maps at semi-detailed and detailed scales (1:50,000 and 1:10,000) do not adequately represent the complexity of the drainage network and the morphological features of karstic areas. This paper evaluates the automated extraction of dolines, typical morphological features of polygonal karst, from digital terrain models generated from stereopairs of aerial photographs at the 1:25,000 scale and from SRTM (Shuttle Radar Topography Mission/NASA) sensor data with resolution of 30 and 90 m. The study area corresponds to the karst plateaus of the Ribeira do Iguape River Valley, southern Sao Paulo state, which contains important remnants of the Atlantic Forest and a rich speleological heritage. The digital terrain model obtained from aerial photographs was generated by the software Geomatica (Module OrthoEngine), using parameters of the internal calibration of the camera and control points extracted from topographic maps at scales of 1:10,000 and 1:50,000, and by GPS (Global Positioning System). Automated extraction of dolines from the models generated from aerial photographs and SRTM data was made in a GIS (Geographic Information System) environment. Based on morphometric analysis, the results were compared with topographical maps at 1:10,000 and 1:50,000 and with conventional photointerpretation. The models generated by Geomatica and SRTM (30 m resolution) detected several dolines not represented in the topographic maps nor in the SRTM (90 m resolution) model, similar to the results of conventional photointerpretation. Thus, the higher the resolution, the more sensitive the method is for extracting the dolines. Comparing the area and perimeter of the dolines, the values obtained by the Geomatica software were very close to those for photointerpretation. The use of different models thus represents an important tool that can help in conventional photointerpretation, especially in regions where there is not detailed cartographic information.

A EROSIVIDADE DAS CHUVAS NOS PLANALTOS CÁRSTICOS DO VALE DO RIO BETARI, IPORANGA (SP)

This paper presents the first estimation of rainfall erosivity calculated from pluviographic data for the karst plateaus of the Betari River. The results were used to fit a probabilistic model for evaluating the occurrence of erosive events and also to develop local models for calculating rainfall erosivity from a single rainfall coefficient (RC). The EI30 values are smaller than those estimated from the model traditionally used to calculate rainfall erosivity in Sao Paulo State.

Mapeamento e caracterização de feições cársticas de superfície na Faixa Itaiacoca nas regiões de Nova Campina e Bom Sucesso de Itararé, SP/PR

This paper presents a characterization of surface karst features identified by detailed aerial photo interpretation (1:25.000) of the carbonate terrains of the Itaiacoca Belt in the Nova Campina and Bom Sucesso de Itarare regions, Sao Paulo and Parana. The main concentrations of sinkholes and closed depressions occur within the urban areas of Nova Campina and Bom Sucesso de Itarare and in the southwestern part of the studied area in the State of Parana. In these areas a polygonal karst pattern, similar to that observed in the Betari River Basin, Upper Ribeira Valley, is present. Morphometric analysis revealed that the closed depressions in general present lower values for area, perimeter, amplitude and slope than those observed in the Lajeado and Andre Lopes belts (Ribeira Valley); circularity indices are higher. Considering the total catchment area of the closed depressions, it was possible to estimate that autochthonous recharge is more important than allochthonous recharge. Diversified land use and occupation in the area require appropriate planning in order to protect the karst. Mapping and characterization of karst features presented in this study constitute the basis for future studies related to the subterranean hydrologic dynamics of karst systems of the region.