Caracterização litofaciológica e paleontológica dos icnossítios Crispim (ou Recanto) e Lagoa do Forno III, Bacia Rio do Peixe, Nordeste do Brasil

Abstract

This study aimed to characterize the lithofacies and paleoichnology of two previously undocumented ichnosites in the Sousa Sub-basin of the Rio do Peixe Basin (RPB), Northeast Brazil: Lagoa do Forno III and Crispim (or Recanto). The RPB is an interior Cretaceous basin formed by tectonic reactivations along Neoproterozoic shear zones. The analyses combined macroscopic rock descriptions, stratigraphic column construction, identification of biogenic and abiogenic sedimentary structures, photogrammetry, 3D modeling of trace fossils, and a lithofacies analysis approach to characterize the deposits. At the Lagoa do Forno III Ichnosite, we identified paleoburrows attributable to small vertebrates, poorly preserved dinosaur footprints, and a fossiliferous layer containing disarticulated and fragmented body fossils, including fish scales and bones, as well as a rib from an indeterminate tetrapod. Meanwhile, the Crispim Ichnosite yielded intermediately preserved tracks and trackways attributed to sauropods, theropods, and ornithopods, along with bioturbation from burrowing invertebrates. The sedimentary packages were assigned to the Rio Piranhas Formation (Lagoa do Forno III) and the Sousa Formation (Crispim) based on integrated lithofacies and sedimentary structure analysis. Notable findings include the first recorded occurrence of paleoburrows and the rare presence of body fossils at the first site, as well as a diverse ichnoassociation at the second site—a pattern poorly documented in the RPB.The results expand our understanding of the paleoichnological diversity of the RPB and reinforce its scientific, heritage, and educational potential. However, the study highlights the urgent need for geoconservation measures and the valorization of regional fossil heritage before significant ichnosites like these are lost to natural and/or anthropogenic processes.