Discriminação dos depósitos cenozoicos da parte emersa da Bacia Paraíba (NE, Brasil) por meio de minerais pesados e granulometria

Abstract

Controversies about the stratigraphy of the Cenozoic deposits of the Paraiba Basin outcropping onshore motivated the analysis of the heavy minerals assemblage and the morphology of zircon and tourmaline grains with the purpose of improve the stratigraphic framework of the basin. These studies revealed strong similarity among the heavy mineral assemblage of the outcropping stratigraphical units (Barreiras Formation and Post-Barreiras I and II units), with the predominance of zircon, tourmaline, kyanite and rutile. An improved stratigraphic discrimination was obtained using morphological analysis of zircon and tourmaline grains, with increasing grain roundness towards younger units. Moreover, the fact that the ZTR index increases gradually towards younger units, and that the RZ index remains constant suggests that older sedimentary units and, subordinately, metamorphic rocks from the Transversal Zone of the Borborema Province are the main sources of the studied Cenozoic sediments.