New record of late Cretaceous vertebrate tracks from the Yacoraite formation (Juella, Quebrada de Humahuaca, northwestern Argentina): aerial drone survey, preservation and sedimentary context

Abstract

The Yacoraite Formation is a worldwide known unit due to the diversity and abundance of vertebrate ichnological record. The complex tectono-sedimentary evolution related to the Andean Cycle generated high dip angles of bedding and, consequently, large tracksites are not easily accessible, making hard the ichnological analysis. Here, we describe a new tracksite named “La Banderita”, near Juella town (Quebrada de Humahuaca, Jujuy, Argentina), where abundant vertebrate and invertebrate trace fossils have been identified on different high slope surfaces. A small, portable unmanned aerial vehicle (UAV) equipped with a digital camera was employed to overcome difficulties in studying traces. After the aerial survey, digital photogrammetry was applied to get 3D models of the trampled surfaces (about 7700 m2 ) and to obtain track distribution maps (more than 100 tracks). As a complement, a detailed 3D model of an easily accessible small area was also made (about 315 m2 ). Trace fossils were preserved within three facies intervals from subtidal/lower intertidal (Intervals I-II) to intertidal (Interval III) settings. In this last interval, quadrupedal (probably sauropod), bipedal (theropod) and undetermined tracks, differently preserved as undertracks, true tracks and natural casts, are identified. These three modes are product of narrow preservational windows, which have prevented weathering destruction process after original trampling. Ichnological and sedimentological data are coherent with those of other localities from the Yacoraite Formation, and suggest that dinosaurs moved along peritidal settings. This contribution highlights the use of aerial drone survey and 3D photogrammetric models, which besides traditional ichnological and sedimentological techniques, allowed a detailed reconstruction of track formation and preservation, contextualizing the trampled surfaces in their palaeoenvironmental setting.