Expressão geofísica do Lineamento Transbrasiliano na porção sul da Bacia Parnaíba

Abstract

This work presents a qualitative interpretation of aeromagnetic and gravity signatures of a segment of the Transbrasiliano Lineament (LTB) in the Parnaiba Basin, North-Northeast Brazil. The LTB represents an elongated NE-SW-oriented feature about 9,700 km long. The present study investigates the geophysical expression of the LTB as a key feature to understand its Mesozoic- Paleozoic evolution and its relationship with the Precambrian basement. The magnetic signature of the Parnaiba Basin is very complex. The magnetic anomalies range from -370 to 238 nT throughout the basin. The magnetic lineaments have a NE-SW principal direction, and subordinate N-S and E-W directions. Thus, four different magnetic fields were characterized using the amplitude map of the analytical signal. The gravity data show a significant gradient in the study area ranging from - 90 mGal to -18 mGal. The regional map of gravity anomalies is characterized by soft anomalies, but with along wavelength, about 450 km. The residual anomaly map highlights gravimetric lineaments related to the structures of the upper crust. These lineaments have major NE-SW direction and subordinate NW-SE. The internal structures of the basin, as depocenters and internal structural highs, are also oriented in the NE-SW direction of the Transbrasiliano Lineament.