Mapeamento geológico de porção da borda norte da bacia do Araripe, nordeste do Brasil

Abstract

Due tothe scientific and industrial interest, the Araripe Basin is a constant target of research. The northern border of the basin, due to its lower production of gypsum and limestone for civil construction, still lacks workson a larger scale of detail. In this context, this paper presents the results of a 1:25,000 scale geological mapping of a portion of the northern border of the Araripe Basin, in Northeastern Brazil, between the citiesof Nova Olinda and Santana do Cariri, state of Ceará. Through the appliedmethodology, six lithostratigraphic units were, one of them belonging to the basin basement formed by gneissic rocks with high angle foliation trend NE-SW, suggesting influence of the Patos Lineament in its structure. Sedimentary units include the MauritiFormation, consisting of ortho and para-conglomeratesof intertwined fluvial depositional environment with unidirectional flow to the NE; The Crato Formation, composed of laminated limestones, marl, shales and sandstones, has root marks in lattice geometry, implying a depositional environment near the palaeo-lakeborder, with subaerial exposure; the Romualdo Formation, composed of sandstones and shales; the Exu Formation, composed of sandstones; and alluvial deposits consisting of clayey land. In general, the study area showed typical stratigraphic stacking sequences of the Araripe Basin. The presence of calcite-filled fractures and textures indicative of seismites in the Crato Formation suggest a possible tectonic influence on the depositional context of this set of lithotypes. Sudden changes in drainage direction suggest a possible neotectonic influence on the area. The activity was successful in characterizing the northern edge portion of the Araripe Basin, contributing to a better understanding of its depositional and post-depositional context and serving as a basis for further in-depth work in the region.