4163 20190314090616.0 10.1016/j.jsg.2019.01.001 DOI SCART-2019-0137 Triantafyllou, A. 3-D digital outcrop model for analysis of brittle deformation and lithological mapping (Lorette cave, Belgium) 2019 Project KARAG we present here a challenging study conducted in one of the main chamber (ca. 10 000 m³) of the Lorette cave (Rochefort, South Belgium). Its roof exhibits an important sedimentary pile that recorded Variscan to recent active brittle tectonics being inaccessible for direct measurements of geological structures. The aims of this research paper is to present a workflow for (i) acquiring data and building a Digital Outcrop Model of a lowlight and geometrically complex cave site using digital photogrammetry, (ii) georeferencing the 3D model in an underground environment, (iii) characterizing the geometry of inaccessible geological structures and their tectonic kinematics(e.g., faults, joints, sedimentary beds) and in fine, (iv) comparing them to accessible structures measured in the field and integrate them into the regional geodynamics. In this paper, the orientation of planar structures will be reported in full strike-dip notation and those of linear structure in full trend-plunge. 3FNRS_AQUIFERES/ 3FNRS_AQUIFERES/ 3FNRS_AQUIFERES NO SfM photogrammetry Brittle structures Paleostress reconstruction Unmanned aerial vehicle Slickenlines analysis Variscan tectonics CloudCompare Cave survey Watlet, A. Le Mouélica, S. Camelbeeck, T. Civeta, F. Kaufmann, O. Quinif, Y. Vandycke, S. Journal of Structural Geology 120 2019 55-66 michel.vancamp@observatoire.be https://doi.org/10.1016/j.jsg.2019.01.001 published in REFERD