The São Pedro tectonostratigraphic terrane: West of the Transversal Zone - Borborema Province

With the present paper, we are completing the description of the basement fractions of the Borborema Province with a discus-sion of the tectonostratigraphic terrane of the central part of the aforementioned province (so-called Transversal Zone), which is partially covered by the Gondwanic sediments of the Parnaíba Syneclise, on most of the western part of the province and of its basement (which is partially composed of paleo-cratonic segments, posing metacratonic behavior, detected by geopysical methods). The basement of this wide tectonostratigraphic terrane ('São Pedro Terrane') is characterized by a complex setting of Archean rock units (western part of it, sheets of Patos do Piauí and Simões, Piauí State) with fast passage to Paleoproterozoic rock units that dominate in the whole eastern domains (Sheets of Ouricuri and Bodocó, Pernambuco State). To the south and southeast of this pre-Paleozoic terrane it is possible to see the development of a straight and long linear belt (SW-NE) the Ouricuri-Bodocó belt. This orogenic belt (of evolution in the Brasiliano cycle) is presenting different linear bands of metasedimentary and volcano-sedimentary rock assemblages at green schist facies (northern band) and amphibolite faceis (southern band), and they are both intruded by various Ediacaran stocks and batholiths. This orogenic belt, to the south, is limited by another Pre-Brasiliano tectonostratigraphic terrane, so-called Icaiçara. Both limits of this Ouricuri–Bodocó belt (northwest and southeast) are strongly marked by shear zones, associated with thrusts. South of Exu, a small perpendicular paleo- rift zone is exposed (as a paleo-aulacogen), now presenting an interesting example of local impactogenic structure. (author)