Structural and geophysical signature of the Northern Portion (Ceará-Piauí border) of the Transbrasiliano Lineament: reactivation in the Parnaíba Basin

Abstract

The Transbrasiliano Lineament is a major shear zone trending NE-SW, related to the Brasiliano orogeny and evolved through high to low temperature stages. In this study, the structural and geophysical signature of the northern segment of Transbrasiliano Lineament was studied in its northern border, between Ceará and Piauí states. In the literature, the phanerozoic reactivation of this structure is commonly referred, generating several late Brasiliano grabens predating the paleozoic Parnaíba syneclisis, like the Jaibaras Graben. Later on, faults that cut the stratigraphic units of the Parnaíba Basin along the entire length of the Transbrasiliano Lineament express its reactivation during successive events. Magnetic map exhibit NE-trending anomalies, interpreted as the signature of the Transbrasiliano Lineament (and Brasiliano structures of the Borborema Province) in its high-temperature expression. The Jaibaras Graben is marked by a straight anomalous track with high magnetic susceptibility, apparently without significant continuity underneath Parnaíba Basin. The geometric and kinematic analysis of the structures in the study area, using remote sensing and field data, led to the characterization of four deformation phases. The Dn deformation phase occurs exclusively in the Jaibaras Graben (constraining its ediacaran-cambrian age), with the development of comparatively higher temperature as regards to the younger events. D1 , D2 and D3 deformation phases affect both the Jaibaras Graben as well as the paleozoic sequences of the northeastern edge of Parnaíba Basin, generating low temperature, essentially brittle/cataclastic structures, which are tentatively correlated with stages of Atlantic opening or to distal orogenic events during the Paleozoic

Keywords

• Transbrasiliano Lineament
• Jaibaras Graben
• Parnaíba Basin.