Abstract:The Central Western Carpathians are characterized by both the thick-and thin-skinned thrust tectonics that originated during the Cretaceous. The Krížna Unit (Fatric Superunit) with a thickness of only a few km is the most widespread cover nappe system that completely overthrusts the Tatric basement/cover superunit over an area of about 12 thousands square km. In searching for a reliable model of its origin and emplacement, we have collected structural data throughout the nappe body from its hinterland backstop (Veporic Superunit) to its frontal parts. Fluid inclusion (FI) data from carbonate cataclastic rocks occurring at the nappe sole provided useful information about the p-T conditions during the nappe transport. The crucial phenomena considered for formulation of our evolutionary model are: (1) the nappe was derived from a broad rifted basinal area bounded by elevated domains; (2) the nappe body is composed of alternating, rheologically very variable sedimentary rock complexes, hence creating a mechanically stratified multilayer; (3) presence of soft strata serving as décollement horizons; (4) stress and strain gradients increasing towards the backstop; (5) progressive internal deformation at very low-grade conditions partitioned into several deformation stages reflecting varying external constraints for the nappe movement; (6) a very weak nappe sole formed by cataclasites indicating fluid-assisted nappe transport during all stages; (7) injection of hot overpressured fluids from external sources (deformed basement units) facilitating frontal ramp overthrusting under supralithostatic conditions. It was found that no simple mechanical model can be applied, but that all known principal emplacement mechanisms and driving forces temporarily participated in progressive structural evolution of the nappe. The rear compression operated during the early stages, when the sedimentary succession was detached, shortened and transported over the frontal ramp. Subsequently, gravity spreading and gliding governed the final nappe emplacement over the unconstrained basinal foreland.
An active gully-related landslide system is located in a deep valley under forest canopy cover. Generally, point clouds from forested areas have a lack of data connectivity, and optical parameters of scanning cameras lead to different densities of point clouds. Data noise or systematic errors (missing data) make the automatic identification of landforms under tree canopy problematic or impossible. We processed, analyzed, and interpreted data from a large-scale landslide survey, which were acquired by the light detection and ranging (LiDAR) technology, remotely piloted aircraft system (RPAS), and close-range photogrammetry (CRP) using the ‘Structure-from-Motion’ (SfM) method. LAStools is a highly efficient Geographic Information System (GIS) tool for point clouds pre-processing and creating precise digital elevation models (DEMs). The main landslide body and its landforms indicating the landslide activity were detected and delineated in DEM-derivatives. Identification of micro-scale landforms in precise DEMs at large scales allow the monitoring and the assessment of these active parts of landslides that are invisible in digital terrain models at smaller scales (obtained from aerial LiDAR or from RPAS) due to insufficient data density or the presence of many data gaps.
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