Paulo Sérgio Gomes Paim

ESTÁGIOS EVOLUTIVOS DA BACIA DO CAMAQUÃ (RS)

This chapter presents a revision of concepts and hypotheses previously presented about the evolution of the Camaqua Basin, central portion of the Rio Grande...

Lowstand Turbidites and Delta Systems of the Itararé Group in the Vidal Ramos region (SC), southern Brazil

Turbidites have captioned the attention of sedimentologists during the last decades due their importance as hydrocarbon reservoirs. However, their relationship to delta systems still deserves further studies. This paper presents examples from a late deglacial to early post-glacial deltaic and turbidite strata exposed in the surroundings of Vidal Ramos (Santa Catarina State, Brazil), southern portion of the Parana Basin. There, the uppermost part of the Mafra Formation and the Rio do Sul Formation onlap the Proterozoic basement and comprises an up to 360 m thick package. It includes (base to top) black shales, mass transport deposits (MTD) and sandy turbidites (Mafra Formation) as well as thin bedded turbidites (tbt), including one interval of black shales and sandy turbidites, overlain by proximal delta front sandstones (Rio do Sul Formation). The analysis of the succession shows two more than 150 m thick coarsening-upwards deltaic successions composed of turbidite sand sheets at their base (prodelta), followed by partially collapsed thin bedded turbidites (delta slope wedge) and delta front sandstones. Both turbidite sand-sheets abruptly overlay black shale intervals related to maximum flooding surfaces and therefore record correlative conformities. A detailed stratigraphic section elaborated from the correlation of four logs (1/100) suggests that distal delta front sands includes both thin bedded turbidites and wave reworked sands whereas the proximal delta front was dominated by long-lived underflows (hyperpycnal flows). The succession suggests that the most expressive turbidite beds (base of the delta systems) have resulted from relative sea-level falls (early lowstand) whereas the thin-bedded turbidites were related to the development of the late lowstand wedge. Black shales represent the transgressive systems tract and HST were not deposited or preserved in the area. High sediment supply associated with lowstand tracts could explain the occasional (Vidal Ramos) to common occurrence of slope failures (slumps and diamictites) involving thin bedded turbidites and delta front sandstones. This situation is quite logical in terms of deglacial periods, and resulting high sediment supply, within a long-term icehouse context, with prevalence of lowstand to transgressive settings.

Contaminação por chorume e sua detecção por resistividade

Resistivity geophysical techniques were applied closed to the Londrinas county sanitary landfill, allowing the detection and mapping of leachate contamination plume. The study area lies on the Parana Basin which is locally represented by basaltic rocks of the Serra Geral Formation. A correlation between lower resistivity values and the supposed leachate contaminations was stablished, once the electrical conduction, under natural conditions, occurs mainly in an ionic way, which are normally presented in the leachate. The main contamination flows in a general SE direction. An unexpected finding of this work was the detection of another flux direction of contamination plume to SW, which flows trough horizontal fractures or alteration surfaces of basaltic contacts.