ANÁLISE ESTRATIGRÁFICA DA BACIA DO ARARIPE, NORDESTE DO BRASIL

Abstract

STRATIGRAHUC ANALYSIS OF ARARIPE BASIN, NORTHEASTERN BRAZIL. The Araripe Basin comprises four main stratigraphic sequences separated by unconformities: 1. a Paleozoic sequence composed of the Cariri Formation; 2. a Juro-Neocomian sequence composed of the Brejo Santo Formation, Missão Velha Formation (redefined) and Abaiara Formation; 3. an Aptian-Albian sequence composed of the Barbalna Formation and Santana Formation; and 4. an Albian-Cenomanian sequence composed of the Exu Formation. The Juro- Neocomian sequence is characterized by horsts and grabens displayed in two sub-basins: Cariri and Serrolândia sub- basins. The Aptian-Cenomanian is characterized by sub-horizontal bedding and localized brittle deformation. The events of sedimentation, erosion, and deformation proposed for the sequences above, integrate the Phanerozoic evolution in Northeastern Brazil. The Paleozoic deposits which have, in attempt, been classified as Upper Ordovician/ Lower Silurian, have also been interpreted as an extension of the cratonic Parnaiba Basin. The Juro-Neoconian sequence is ú» sedimentary response to the mechanical subsidence brought about by the Gondwana rifting processes. The Barbalha and Santana formations comprise a transgressive-regressive cycle characterized by short-lived sea ingression which has deposited an exuberant fossiliferous carbonate concretions level and extensive gypsum beds. The presence of alluvial deposits of Exu Formation, deposited contemporaneously to a global eustatic sea level rising, suggests an epeirogenic uplift early in the Albian-Cenomanian time.