LITHOSTRATIGRAPHIC CONTEXT AND PRELIMINARY CONSIDERATION OF THE FORMATION OF THE FOSSILIFEROUS DEPOSITS IN THE MUNICIPALITY OF CRUZEIRO DO OESTE, STATE OF PARANÁ

Abstract

The objective of the present study was the stratigraphic contextualization of the fossiliferous deposit and the interpretation of the deposition conditions, as well as the lithofaciological relationships of the sedimentary sequence of the Rio Paraná Formation, with emphasis on the paleontological site in Cruzeiro do Oeste, Paraná. From the results obtained, it was found that the outcrop is represented by a rhythmic sequence of centimetric strata, predominantly composed of fine sand, forming a sequence of at least three strata, interspersed by millimetric clayey levels with hematite, rich in pterosaur fossils. The chaotic arrangement of these elements near the top of each stratum indicates a deposition under water overflow conditions, with distal ephemeral surface runoff, which we call Lithofacies of Floodplain. This lithofacies transitionally grades upwards to a fine sandy sequence with tenuous sedimentary structures associated with wave marks in the basal part of the layer. This sequence was interpreted as Lithofacies of Sand Sheetes, deposited initially in conditions of higher substrate humidity and grading to drier conditions towards the top.