Experience of Using Large-Scale Aerial Photography and Multiple Photography to Study Linear Folding in the Talas Range of the Tien Shan

Abstract

To address tectonics and geodynamic issues related to the formation of crystalline continental crust, linear folding is studied using field structural geology methods in both hard-copy and digital formats. Using the example of Caledonian fold structures in the Talas Range of the Northern Tien Shan, the results of using several methods for collecting data on the morphology of folded and faulted structures of varying scales are demonstrated. To compile short sections of a structural profile at a scale of 1 : 10 000 to 1 : 1000, conventional measurements of bedding elements (paper techniques) are used in combination with UAV aerial photography of complex areas. UAV photography and multiple digital camera shooting are used to characterize the hinges of large folds with limb widths of up to 0.5 to 1 km. These two types of photographs are transformed using the Agisoft Metashape software into 3D photomodels of these structures, suitable for office study. Multiple photography is also used to study the deformation of minor folds. The resulting description of the structural material at the digital model level is more accurate than recording structures using paper-based technologies, and the material is recorded much more quickly. The results are discussed in relation to the problem of determining the magnitude of shortening for structures of different scales: from “structural cells” (3–5 km along the profile) to small folds measuring a few centimeters.