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A large‐scale array of long‐period magnetic data and a deep‐probing magnetotelluric profile were recorded in the intracratonic Paraná sedimentary basin in central eastern South America, which presents a thick and extensive sedimentary‐magmatic sequence that allows its basement to be investigated only by indirect methods. Integration of the results from both methods showed that the crust beneath the basin presents several quasi‐linear highly conductive channeled zones with limited lateral extent, in coincidence with some of the main tectonic structures recognized at the surface, and a moderate but pervasive lithosphere conductivity enhancement beneath its central part. Upward movement of CO2‐bearing volatiles and magmas precipitating highly conducting mineral phases along discrete subvertical fault zones that served as feeder conduits for Early Cretaceous voluminous continental flood basalts was a likely process responsible for the localized conductivity enhancements. Correlation between some of the linear conductive zones and elongated magnetic anomalies and between the maximum depth occurrence of most of these conductive anomalies and the Curie depth at which crustal rocks lose their magnetism gives strong support to interconnected iron oxides (especially magnetite) and iron sulfides (such as pyrrhotite) as the main conductive sources. The moderate bulk conductivity increase in the crust and upper mantle beneath the central part of the basin is unexpected for a postulated cratonic basement and is tentatively associated with impregnation of the lithosphere by conducting minerals related either to widespread tectonic events in the Ordovician or Late Precambrian or to dispersed magmatic residues of an Early Cretaceous magma differentiation contaminating the entire lithosphere. Conductivity structure imaged under a basin covered with extensive magmatismQuasi‐linear conductive zones served as feeder conduits for basaltic extrusionCrust beneath the central part of the basin impregnated by conducting minerals

Magnetotelluric (MT) soundings were carried out in the period range of 20 to 6000 s along profiles roughly orthogonal to the Campos do Jordão Railway (CJRW), in the Brazilian southeastern region. The profiles were located over two adjacent regions with contrasting conductivity, the conductive sedimentary region of the Taubaté Basin and the resistive crystalline region of the Serra da Mantiqueira. The railway operates with DC current that produces an intense electromagnetic noise but only during diurnal periods, being turned off at night. The objective of this study is to characterize the CJRW noise in order to verify its effect on MT parameters. It was inferred that the entire length of the Taubaté Basin is probably affected by the noise, whereas in the crystalline terrains the noise reaches distances in the range of 76 to 126 km. The electric channels show a strong dependence on geology which is suggestive of the potential application of the CJRW as a controlled source in geophysical studies. The data were processed with modern techniques presently available to the scientific community. Under the conditions of the present study, it was observed that the robust Single Station technique is as efficient as the robust Remote Reference to remove the kind of noise generated by the CJRW, an intense perturbation that affects only some well-defined portions of the time series. Finally, the analyses reaffirm the necessity of a careful choice of the station to be used as reference in the Remote Reference technique.