Unmanned aerial vehicle oblique photography‐based superposed fold analysis of outcrops in the Xuhuai region, North China

Abstract

Unmanned aerial vehicle (UAV) oblique photography technology is widely utilized in various fields owing to such advantages as true three‐dimensional (3D), high precision, and low expenses. We explored the application of UAV oblique photography in the superposed fold analysis conducted in the Xuhuai region. Three feasible and time‐efficient steps were established to fulfil the task. The tile images from UAV oblique photography are first synthesized on the Altizure website into a 3D outcrop model, which is then imported into ArcScene to extract bedding and lineation attitudes by GeoAnalysis Tools. The fold geometry and superposed style were characterized and analysed based on the 3D model, followed by extending the 3D structure morphology across the entire outcrop scale and illustrating the superposition style and sequence in the GOCAD platform. The geological conclusions were drawn by applying the method for analysing two outcrops in the Xuhuai region. Two phases of folds were identified, with the first generation nearly E‐W‐trending oblique‐recumbent folds overprinted by the second‐generation NNE‐NE‐trending wide and upright folds. The nearly E‐W‐striking fold is inferred to be related to the compressive orogeny in the Dabie Orogenic Belt in the Triassic. The NNE‐NE‐striking fold is related to the northwest subduction of the Pacific Plate or the northward thrust of the Sulu Orogenic Belt in the Jurassic. This example demonstrates that UAV oblique photography is a powerful and reliable method for structural analysis at the outcrop scale, especially for the inaccessible outcrops with weak vegetation cover.