Digital modelling and visualization of three-dimensional sedimentary geometries. The Gorgo a Cerbara palaeoescarpment (Monte Nerone, Umbria-Marche Apennine)

In recent years, methodologies for three-dimensional digitization of geological objects have considerably grown, giving to geologists several cutting-edge approaches for collecting and manipulating field evidences, and obtaining models starting from a huge amount of raw data. Parallel to the management of field data, digital modelling proves to be a valuable tool, making the raw geological data communicable in interactive mode, and the information retrievable, and allowing to preserve sometimes unique clues of regional or global importance. This methodological enhancement could be dramatically significant in highly complex settings such as the Apennines. In the case study here presented, highresolution Digital Photogrammetry method was applied to a well-studied, key-outcrop from the Umbria-Marche Apennine. The method allows building a full three-dimensional metric model of any object in space, starting from a suitable number of photographic images (2D object projection) of a static scene taken from different points of view. The technique produces high quality dense point clouds used to generate 3D models comparable to those obtained from LiDAR technology. The concerned site is the Gorgo a Cerbara section (Piobbico, PU), where the NW-facing Jurassic escarpment of the Monte Nerone Pelagic Carbonate Platform (PCP) is magnificently exposed. Here, the Jurassic-Lower Cretaceous basin-fill succession rests on the morpho-structural high margins. The analysed outcrop represents the lowermost tract of the exposed paleoescarpment, and consists of an irregular, silicified, palaeo-surface of pre-rift ‘Calcare Massiccio’. On it rests small patches of ‘Calcare Massiccio B’ facies (drowning succession of footwall-blocks), earliest Pliensbachian in age, and of upper Sinemurian cephalopod-rich pelagites, in the form of epiescarpment deposits. The whole complex is then unconformably covered by basin-fill pelagites of the Corniola Fm., late Pliensbachian in age. The photogrammetric models return in detail the astonishing stratigraphical, sedimentological and taphonomical framework observed in the field. The complex sedimentary evolution of a PCP margin and the processes triggered within PCP/basin systems are accurately reproduced. Moreover, as ‘natural’ operation when dealing with digital stuff, all the evidence can be displayed from different perspectives with the same high confidence, further helping in the reconstruction of three-dimensional geometries which is based, as praxis, on field observations and evidence collection. High-resolution photogrammetric techniques further proven to be one the best future candidates, the most low-cost/high-performance, for modelling and visualizing the phenomenological world in the field of geology and palaeontology (but in all the geosciences sensu lato) and to construct wide-ranging three- and four-dimensional models rooted on fieldwork, to be used for visualizing geological inferences and reconstructions.