Aspectos tafonômicos e paleoecológicos de ninfas de ephemeroptera e odonata do membro Crato, formação Santana, Bacia do Araripe, (Cretáceo inferior)

Abstract

The Crato Member of the Santana Formation, Araripe Basin, has one of the best and most important fossil deposit of Lower Cretaceous and presents remarkable geological site. The fossils contained in this unit are relatively abundant and diverse, including invertebrates, vertebrates and plants. The depositional system proposed for that unit is a lacustrine sequence, predominantly carbonate, consisting of cálcilutite alternating with rhythmites clayey, shales and fine sandstones. This study aims to investigate the relationship between anoxia condition (reducing agent of the post-mortem scavenger activity) in the ofodonata larvae and ephemeroptera occurrence in limestone layers CratoMember, belonging to the collection of the Paleontology Laboratory of the UFC. The relevance of this study is the comparison of the paleontological record of larvae odonata and ephemeroptera with its living equivalents, as they are extremely sensitive to environments with low oxygen concentration and commonly found in rivers and / or shallow lakes. Thus, according to the Principie of Actualism, the Odonata and Ephemeroptera Cretaceous should also exhibit a preferente for similar environments. The reduced occurrence of bioturbation observed in layers of laminated limestone is explained by the existing anoxic condition in the lake boftom, but the presence of larvae of Odonata and Ephemeroptera, and the taphonomic aspects related to them does not corroborate this idea. This paper seeks evidente, based on the fossil record, which can contribute to a reconstruction of the Crato Member paleoenvironment during the Lower Cretaceous.