Abstract Tectonic rejuvenation has been widely described in ancient rifting areas of intraplate settings, despite extensive active tectonics being discontinued long ago. Various models have been invoked to justify such tectonic rejuvenation, suggesting that the long-term deformation in intraplate interiors may be more complex than once supposed. Inherited weakness zones, e.g., pre-existing faults are stress concentrators. However, not all weakness zones in plate interiors show tectonic rejuvenation and recognizing intraplate fault reactivation remains puzzling. Bedrock channels play an essential role in tectonically unstable landscapes and therefore they may unveil which pre-existing structures have been rejuvenated. Here we explore the Cinzas Catchment in order to investigate the interactions between tectonic rejuvenation, bedrock inheritance and geomorphic river signatures in an important Brazilian rifting feature, the Ponta Grossa Arch. We perform a geomorphic analysis combined with fieldwork, dating techniques and existing data to evaluate whether the geomorphic responses of the major rivers show perturbations related to the bedrock inheritance and post-rift rejuvenation. We also show that the interactions between river signatures and the bedrock fault zones are responses to post-rifting rejuvenation coupled with bedrock inheritance. This post-rifting rejuvenation is consistent with a mosaic of superimposed mechanisms which have been invoked by previous studies.

Resumo Este artigo apresenta os resultados do mapeamento das rotas de fluxo do escoamento superficial em área caracterizada por intensas modificações do relevo causadas por intervenções antrópicas. Como estudo de caso foi escolhida a alta bacia do córrego Tucum (São Pedro - SP), por apresentar um cenário marcado pelo avanço da urbanização sobre terrenos com forte suscetibilidade à erosão, com a presença de feições erosivas lineares (ravinas e voçorocas), e um complexo histórico de intervenções buscando o controle de tais processos. Foram utilizados dados primários, obtidos a partir de levantamento topográfico em campo, e executadas operações visando à elaboração de um Modelo Digital de Elevação Hidrologicamente Consistente (MDEHC), no programa ArcGIS 10.1. Em seguida, foi elaborada a Carta de Fluxo Concentrado da área, a partir da modelagem através do algoritmo Multiple Flow, no programa ArcView 3.2. Os resultados permitiram constatar que feições topográficas de detalhe, em especial, terraços tecnogênicos, têm exercido controle marcante sobre as rotas de fluxo do escoamento superficial, contribuindo para a geração de vetores de avanço erosivo das ravinas e voçorocas existentes na área.

Abstract This article presents the results of mapping the flow routes of surface runoff in an area characterized by profound changes in relief caused by anthropic interventions. We chose the Tucum stream upper basin (Sao Pedro, São Paulo - Brazil) as a case study because it is marked by the advance of urbanization on land with strong susceptibility to erosion, with the presence of linear erosive features (ravines and gullies) and a complex history of interventions seeking to control them. We obtained primary data from a topographic survey in the field and carried out operations to develop a Hydrologically Consistent Digital Elevation Model (HCDEM) in the ArcGIS 10.1 program. Then, the Concentrated Flow Map of the area was elaborated from the modeling using the Multiple Flow algorithm in the ArcView 3.2 program. The results showed that topographic features of detail, especially technogenic terraces, have exercised marked control over the flow routes of surface runoff, contributing to generating erosive advance vectors of the ravines and gullies.

Uma forma de se observar as alterações humanas na superfície é por meio do estudo dos depósitos tecnogênicos. No caso de Presidente Prudente – SP foram estudadas duas formações tecnogênicas em planícies aluviais alteradas no entorno do perímetro urbano, nos seguintes loteamentos: Parque Residencial Francisco Belo Galindo e Vila Nova Prudente. Além de trabalhos de campo para o reconhecimento dos aspectos socioambientais, foram realizadas coletas de amostras dos depósitos tecnogênicos utilizando tubos de PVC de seis polegadas e com um metro de comprimento. Através dos trabalhos de campo e de análises físicas (texturais) realizadas em laboratório, identificou-se no Parque Residencial Francisco Belo Galindo, a presença de artefatos úrbicos (resquícios de concretos, plásticos, etc.) e material sedimentar, cuja classe textural predominante é “franco arenosa”. No caso da Vila Nova Prudente, identificou-se também artefatos úrbicos (fragmentos de concretos, plásticos, etc.) e material sedimentar, cuja classe textural predominante é “areia”. Com os dados obtidos nos levantamentos de campo e nas análises laboratoriais, foi possível a compreensão dos fatores presentes direta e indiretamente na formação dos depósitos tecnogênicos.

One way to observe the human changes on the Earth surface is by studying the technogenic deposits. Concerning Presidente Prudente - SP, two technogenic formations in altered floodplains, surrounding the urban perimeter, in the following settlements were studied: Parque Residencial Francisco Belo Galindo and Vila Nova Prudente. Beside the fieldworks to recognition of the social environmental aspects, samples of technogenic deposits were collected using six-inch-PVC tubes, with one meter in length. Through the fieldworks and physical analyses (textural) performed in laboratory, it was identified the presence of urbic artifact (holdover of concrete, plastics, etc.) and sedimentary materials in Parque Residencial Francisco Belo Galindo, whose predominant textural class is “sandy loam”. In Vila Nova Prudente, whose predominant textural class is “sandy”, urbic artifacts (holdover of concrete, plastics, etc.) sedimentary materials were also identified. With the data obtained in the field survey and laboratorial analyses, it was possible to understand the direct and indirect presence of factors in the formation of technogenic deposits.