Gênese dos níveis coquinóides do membro romualdo, formação santana, na porção central e leste da bacia do Araripe

Abstract

The fundamental aim of this research is to provide subsidies that contribute to determinate the genesis of the coquinoid levels identified in the Romualdo Member, Santana Formation, Araripe Basin. Therefore, activities were developed for sampling at different points of the center and eastern border of the basin, to produce petrographic and sedimentological data that could establish inferences and deductions about constituents, features and structures identified on the rocks. It was considered the main related researches already developed, aiming the association with pre-existing data for the interpretations. Identifying the characteristics of macrofossils concentrations for each sample, and comparing them, it was possible to suggest an origin for the formation of these materials from the episodic occurrence of storms, with products characterized according to the major/minor influence of the transport vector and interference from specific paleogeographical factors. The petrographic analysis determined the lithotypes, ranging from bioclastics packstones to bioclastics wackstones, with highly demicritized portions originating grainstones. Overall, may also be interpreted as biomicrites. The taphonomical parameters analyzed, together with the siliciclastic content, suggest a transitional paleoenvironment system and a complex deposition dynamic, associated with the occurrence of rapid sedimentation events and constant reworking espisodes influenced by storms, which contributed to increase the transport energy. It was considered the Tethyan waters influence for the marine interference in this paleoenvironment during the Aptian transgression, playing an important role in the transport and depositional dynamics. The coquinoid levels are also found in others portions of the Araripe Basin (not so only in Cearense portion). Thus, a more detailed analysis for the origin of these concentrations is something more complex to treat, even more considering a magnified paleobiogeografic domain