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© 2016 Geological Society of America. Different remote sensing technologies, including photogrammetry and LIDAR (light detection and ranging), allow collecting three-dimensional (3D) data sets that can be used to create 3D digital representations of outcrop surfaces, called digital outcrop models (DOM). The main advantages of photogrammetry over LIDAR are represented by the very simple and lightweight field equipment (a digital camera), and by the arbitrary spatial resolution, that can be increased simply getting closer to the outcrop or by using a different lens. The quality of photogrammetric data sets obtained with structure from motion (SFM) techniques has shown a tremendous improvement over the past few years, and this is becoming one of the more effective ways to collect DOM data sets. The Vajont Gorge (Belluno Dolomites, Italy) provides spectacular outcrops of jurassic limestones (Vajont Limestone Formation) in which mesozoic faults and fracture corridors are continuously exposed. Some of these faults acted as conduits for fluids, resulting in structurally controlled dolomitization. A 3D DOM study, based on a photogrammetric SFM data set, was carried out, aimed at enabling interdisciplinary characterization and reconstruction of coupled brittle deformation and fluid flow processes. For this study we used a DOM (730 m × 360 m × 270 m) consisting of continuous triangulated surfaces representing the outcrop, textured with highresolution images. Interpretation and modeling performed on this data set include (1) georeferencing of structural measurements and sampling stations; (2) tracing of stratigraphic boundaries, structural surfaces, and dolomitization fronts (ground-truthed); (3) correlation and extrapolation of realistic 3D surfaces from these traces; and (4) development of a 3D geological model at the scale of the Vajont Gorge, including stratigraphy, faults, dolomitization fronts, and volumetric meshes suitable for the statistical analysis of structural, diagenetic, and geochemical parameters. The DOM study highlighted the close relationship between faults and dolostone geobodies, demonstrating that dolomitization was guided by fluid infiltration along Mesozoic normal faults. In order to explore the uncertainty associated with the 3D model of irregularly shaped dolostone bodies, three different 3D dolostone geobody realizations have been modeled, providing a minimum, intermediate, and maximum estimate of the dolostone/limestone volumetric facies ratio, while honoring the field constraints. ispartof: Geosphere vol:11 issue:6 pages:2031-2048 status: published

We investigate the processes of growth and consumption of rifted stratovolcanoes to better understand their morphostructural and geological evolution in relation to sheet intrusions. Field data collected from four rifted volcanoes, located in Italy and Chile, and representing structural end members, are integrated with scaled physical models and numerical three-dimensional (3D) modeling. Due to preferential along-rift magma pathways, volcanoes grow perpendicular to rift strike mostly by intrusions, and parallel to the rift mostly by effusions. These constructive processes are partially or fully balanced by destructive processes that occur both perpendicular to the rift and along the rift zone, and that are initiated by the sheet intrusions. Field data indicate that sheets and/or fl ank eruptions increase in number approaching the summit part of a cone. Since dyking within a volcano causes a magmatic driving overpressure and lateral displacement/deformation of the cone fl ank, this displacement is assumed to be greater where intrusions have the highest frequency. Lateral deformation can also lead to fl ank failure along a deep-seated slip surface. Symmetrical rifts may produce deep-seated collapses in opposing directions, while asymmetrical rifts can preferentially lead to destruction on the tectonically downthrown side. If the collapse depression is refi lled by new volcanism, the cone attains a new critical height (and mass), setting the scene for renewed failure. This sequence inhibits the cone from widening normal to the rift zone. The fi eld examples studied, plus analog and numerical modeling, also indicate that dyking within the rift zone destabilizes the volcano fl anks along the rift: where dyke tip stresses approach the slope, surface landsliding might be induced. This in turn produces debuttressing above the dyke, favoring effusive eruptions and lavas fl owing within the landslide depression. In this case a balance can occur between new lava outpourings and gravity mass removal, or the volcano can grow along the rift if the emitted magma volume is higher than the collapsed material. From a mechanical point of view, the different behavior of volcanic slopes, both parallel to and perpendicular to dyke strike, is a function of magma forces and the cumulative dyke-induced displacement. The combination of along-rift-strike landsliding and normal-to-rift deep-seated large-scale lateral collapse, characteristically produces in map view four main zones of "consumption" and "rebuilding" on the volcano. These alternate with four triangular sectors where the volcano slopes are relatively more stable. When volcanic activity ends, cone consumption is concentrated along the rift and is favored by fault slip or channeled erosion. © 2010 Geological Society of America.