Aptian marine ingression in the Araripe Basin: Implications for paleogeographic reconstruction and evaporite accumulation

Abstract

Abstract Integrated sedimentologic and palynological analysis of four outcrops in the Aptian succession of the Araripe Basin provides information on the earliest marine connection of this basin. Palynological samples revealed well-preserved palynomorphs with diverse assemblages composed of pteridophyte spores and gymnospermic pollen grains, especially Classopollis, besides phytoclasts and abundant amorphous organic matter. Microforaminiferal linings were retrieved from two samples, both from the Santana Formation, immediately underlying the “Ipubi Layers”. The few specimens recognized are well preserved, very similar to each other in size and shape (trochospiral morphology), and usually embedded within amorphous organic matter. These records indicate that the lower Crato Member was deposited in a marine environment. The increasing marine influence in the Araripe Basin, coupled with increasing aridity, allowed the accumulation of evaporites (“Ipubi Layers”) in restrict portions of the basin. The small size of the inferred marine connection is probably why it has been so difficult to identify its precise geographic location.