Autor(es): Nascimento Junior, Daniel Rodrigues do ; Silva Filho, Wellington Ferreira da ; Freire Junior, José Gervásio ; Santos, Felipe Holanda dos
Data: 2022
Origem: Oasisbr
Assunto(s): Evaporites; Gypsum; Ceará State (Brazil); Araripe Basin; Ipubi Formation
The Ipubi Formation in the Araripe Basin (Northeast Brazil) has evaporite-lutite successions rich in gypsum, a mineral of great regional economic relevance, a highlighted stratigraphic mark, and also a natural boundary for underlying successions potentially analogous to “Pre-Salt” hydrocarbon reservoirs of the Brazilian coastal basins. In this study, syngenetic and diagenetic aspects of the Ipubi Formation at Santana do Cariri (Ceara State) were investigated by means of facies analysis, petrography, and miner- alogical/chemical analyses of evaporites and shales.The results show that the contact relationship between evaporites and marly shales, without signs of subaerial exposure and laterally adjacent, was associated with shallow, calm and somewhat anoxic waterbodies, locally salt-supersaturated (brines) but under seasonal variations of water levels. This scenario could have shared place with hydrothermal phenomena in a playa lake depositional system. Regarding diagenesis, although there is evidence supporting pseudomorphic replacement of gypsum by anhydrite, the burial of the Ipubi Formation would have been limited due to the frequent occurrence of gypsum without any trace of chemical replacement.
